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</CENTER>
<HR>
<H3>2. Getting Started
</H3>
<P>This section describes how to build and run LAMMPS, for both new and
experienced users.
</P>
2.1 <A HREF = "#start_1">What's in the LAMMPS distribution</A><BR>
2.2 <A HREF = "#start_2">Making LAMMPS</A><BR>
2.3 <A HREF = "#start_3">Making LAMMPS with optional packages</A><BR>
2.4 <A HREF = "#start_4">Building LAMMPS via the Make.py script</A><BR>
2.5 <A HREF = "#start_5">Building LAMMPS as a library</A><BR>
2.6 <A HREF = "#start_6">Running LAMMPS</A><BR>
2.7 <A HREF = "#start_7">Command-line options</A><BR>
2.8 <A HREF = "#start_8">Screen output</A><BR>
2.9 <A HREF = "#start_9">Tips for users of previous versions</A> <BR>
<HR>
<HR>
<H4><A NAME = "start_1"></A>2.1 What's in the LAMMPS distribution
</H4>
<P>When you download a LAMMPS tarball you will need to unzip and untar
the downloaded file with the following commands, after placing the
tarball in an appropriate directory.
</P>
<PRE>gunzip lammps*.tar.gz
tar xvf lammps*.tar
</PRE>
<P>This will create a LAMMPS directory containing two files and several
sub-directories:
</P>
<DIV ALIGN=center><TABLE BORDER=1 >
<TR><TD >README</TD><TD > text file</TD></TR>
<TR><TD >LICENSE</TD><TD > the GNU General Public License (GPL)</TD></TR>
<TR><TD >bench</TD><TD > benchmark problems</TD></TR>
<TR><TD >doc</TD><TD > documentation</TD></TR>
<TR><TD >examples</TD><TD > simple test problems</TD></TR>
<TR><TD >potentials</TD><TD > embedded atom method (EAM) potential files</TD></TR>
<TR><TD >src</TD><TD > source files</TD></TR>
<TR><TD >tools</TD><TD > pre- and post-processing tools
</TD></TR></TABLE></DIV>
<P>Note that the <A HREF = "download">download page</A> also has links to download
Windows exectubles and installers, as well as pre-built executables
for a few specific Linux distributions. It also has instructions for
how to download/install LAMMPS for Macs (via Homebrew), and to
download and update LAMMPS from SVN and Git repositories, which gives
you the same files that are in the download tarball.
</P>
<P>The Windows and Linux executables for serial or parallel only include
certain packages and bug-fixes/upgrades listed on <A HREF = "http://lammps.sandia.gov/bug.html">this
page</A> up to a certain date, as
stated on the download page. If you want an executable with
non-included packages or that is more current, then you'll need to
build LAMMPS yourself, as discussed in the next section.
</P>
<P>Skip to the <A HREF = "#start_6">Running LAMMPS</A> sections for info on how to
launch a LAMMPS Windows executable on a Windows box.
</P>
<HR>
<H4><A NAME = "start_2"></A>2.2 Making LAMMPS
</H4>
<P>This section has the following sub-sections:
</P>
<UL><LI><A HREF = "#start_2_1">Read this first</A>
<LI><A HREF = "#start_2_2">Steps to build a LAMMPS executable</A>
<LI><A HREF = "#start_2_3">Common errors that can occur when making LAMMPS</A>
<LI><A HREF = "#start_2_4">Additional build tips</A>
<LI><A HREF = "#start_2_5">Building for a Mac</A>
<LI><A HREF = "#start_2_6">Building for Windows</A>
</UL>
<HR>
<A NAME = "start_2_1"></A><B><I>Read this first:</I></B>
<P>If you want to avoid building LAMMPS, read the preceeding section
about options available for downloading and installing executables.
Details are discussed on the <A HREF = "download">download</A> page.
</P>
<P>Building LAMMPS can be simple or not-so-simple. If MPI is already
installed on your machine (or you just want to run LAMMPS in serial)
and you can use one of the provided machine Makefiles and the build
works on your platform, then it's simple.
</P>
<P>If you want to do one of these:
</P>
<UL><LI>use optional LAMMPS features that require additional libraries
<LI>use optional packages that require additional libraries
<LI>use optional accelerator packages that require special compiler/linker settings
<LI>run on a specialized platform like a supercomputer that has its own compilers, settings, or other libs to use
</UL>
<P>then building LAMMPS is more complicated. You may need to find where
auxiliary libraries exist on your machine or install them if they
don't. You may need to build additional libraries that are part of
the LAMMPS package, before building LAMMPS. You may need to edit a
machine Makefile to make it compatible with your system.
</P>
<P>Please read the following sections carefully. If you are not
comfortable with makefiles, or building codes on a Unix platform, or
running an MPI job on your machine, please find a local expert to help
you. Many compilation, linking, and run problems that users have are
often not really LAMMPS issues - they are peculiar to the user's
system, compilers, libraries, etc. Such questions are better answered
by a local expert.
</P>
<P>If you have a build problem that you are convinced is a LAMMPS issue
(e.g. the compiler complains about a line of LAMMPS source code), then
please post the issue to the <A HREF = "http://lammps.sandia.gov/mail.html">LAMMPS mail
list</A>.
</P>
<P>If you succeed in building LAMMPS on a new kind of machine, for which
there isn't a similar machine Makefile included in the src/MAKE
directory, then send it to the developers and we can include it in the
LAMMPS distribution.
</P>
<HR>
<A NAME = "start_2_2"></A><B><I>Steps to build a LAMMPS executable:</I></B>
<P><B>Step 0</B>
</P>
<P>The src directory contains the C++ source and header files for LAMMPS.
It also contains a top-level Makefile and a MAKE sub-directory with
low-level Makefile.* files for many machines. From within the src
directory, type "make" or "gmake". You should see a list of available
choices. If one of those is the machine and options you want, you can
type a command like:
</P>
<PRE>make linux
or
gmake mac
</PRE>
<P>Note that on a multi-processor or multi-core platform you can launch a
parallel make, by using the "-j" switch with the make command, which
will build LAMMPS more quickly.
</P>
<P>If you get no errors and an executable like lmp_linux or lmp_mac is
produced, you're done; it's your lucky day.
</P>
<P>Note that by default only a few of LAMMPS optional packages are
installed. To build LAMMPS with optional packages, see <A HREF = "#start_3">this
section</A> below.
</P>
<P><B>Step 1</B>
</P>
<P>If Step 0 did not work, you will need to create a low-level Makefile
for your machine, like Makefile.foo. You should make a copy of an
existing src/MAKE/Makefile.* as a starting point. The only portions
of the file you need to edit are the first line, the "compiler/linker
settings" section, and the "LAMMPS-specific settings" section.
</P>
<P><B>Step 2</B>
</P>
<P>Change the first line of src/MAKE/Makefile.foo to list the word "foo"
after the "#", and whatever other options it will set. This is the
line you will see if you just type "make".
</P>
<P><B>Step 3</B>
</P>
<P>The "compiler/linker settings" section lists compiler and linker
settings for your C++ compiler, including optimization flags. You can
use g++, the open-source GNU compiler, which is available on all Unix
systems. You can also use mpicc which will typically be available if
MPI is installed on your system, though you should check which actual
compiler it wraps. Vendor compilers often produce faster code. On
boxes with Intel CPUs, we suggest using the commercial Intel icc
compiler, which can be downloaded from <A HREF = "http://www.intel.com/software/products/noncom">Intel's compiler site</A>.
</P>
<P>If building a C++ code on your machine requires additional libraries,
then you should list them as part of the LIB variable.
</P>
<P>The DEPFLAGS setting is what triggers the C++ compiler to create a
dependency list for a source file. This speeds re-compilation when
source (*.cpp) or header (*.h) files are edited. Some compilers do
not support dependency file creation, or may use a different switch
than -D. GNU g++ works with -D. If your compiler can't create
dependency files, then you'll need to create a Makefile.foo patterned
after Makefile.storm, which uses different rules that do not involve
dependency files. Note that when you build LAMMPS for the first time
on a new platform, a long list of *.d files will be printed out
rapidly. This is not an error; it is the Makefile doing its normal
creation of dependencies.
</P>
<P><B>Step 4</B>
</P>
<P>The "system-specific settings" section has several parts. Note that
if you change any -D setting in this section, you should do a full
re-compile, after typing "make clean" (which will describe different
clean options).
</P>
<P>The LMP_INC variable is used to include options that turn on ifdefs
within the LAMMPS code. The options that are currently recogized are:
</P>
<UL><LI>-DLAMMPS_GZIP
<LI>-DLAMMPS_JPEG
<LI>-DLAMMPS_PNG
<LI>-DLAMMPS_FFMPEG
<LI>-DLAMMPS_MEMALIGN
<LI>-DLAMMPS_XDR
<LI>-DLAMMPS_SMALLBIG
<LI>-DLAMMPS_BIGBIG
<LI>-DLAMMPS_SMALLSMALL
<LI>-DLAMMPS_LONGLONG_TO_LONG
<LI>-DPACK_ARRAY
<LI>-DPACK_POINTER
<LI>-DPACK_MEMCPY
</UL>
<P>The read_data and dump commands will read/write gzipped files if you
compile with -DLAMMPS_GZIP. It requires that your machine supports
the "popen" function in the standard runtime library and that a gzip
executable can be found by LAMMPS during a run.
</P>
<P>If you use -DLAMMPS_JPEG, the <A HREF = "dump_image.html">dump image</A> command
will be able to write out JPEG image files. For JPEG files, you must
also link LAMMPS with a JPEG library, as described below. If you use
-DLAMMPS_PNG, the <A HREF = "dump.html">dump image</A> command will be able to write
out PNG image files. For PNG files, you must also link LAMMPS with a
PNG library, as described below. If neither of those two defines are
used, LAMMPS will only be able to write out uncompressed PPM image
files.
</P>
<P>If you use -DLAMMPS_FFMPEG, the <A HREF = "dump_image.html">dump movie</A> command
will be available to support on-the-fly generation of rendered movies
the need to store intermediate image files. It requires that your
machines supports the "popen" function in the standard runtime library
and that an FFmpeg executable can be found by LAMMPS during the run.
</P>
<P>Using -DLAMMPS_MEMALIGN=<bytes> enables the use of the
posix_memalign() call instead of malloc() when large chunks or memory
are allocated by LAMMPS. This can help to make more efficient use of
vector instructions of modern CPUS, since dynamically allocated memory
has to be aligned on larger than default byte boundaries (e.g. 16
bytes instead of 8 bytes on x86 type platforms) for optimal
performance.
</P>
<P>If you use -DLAMMPS_XDR, the build will include XDR compatibility
files for doing particle dumps in XTC format. This is only necessary
if your platform does have its own XDR files available. See the
Restrictions section of the <A HREF = "dump.html">dump</A> command for details.
</P>
<P>Use at most one of the -DLAMMPS_SMALLBIG, -DLAMMPS_BIGBIG, -D-
DLAMMPS_SMALLSMALL settings. The default is -DLAMMPS_SMALLBIG. These
settings refer to use of 4-byte (small) vs 8-byte (big) integers
within LAMMPS, as specified in src/lmptype.h. The only reason to use
the BIGBIG setting is to enable simulation of huge molecular systems
(which store bond topology info) with more than 2 billion atoms, or to
track the image flags of moving atoms that wrap around a periodic box
more than 512 times. The only reason to use the SMALLSMALL setting is
if your machine does not support 64-bit integers. See the <A HREF = "#start_2_4">Additional
build tips</A> section below for more details.
</P>
<P>The -DLAMMPS_LONGLONG_TO_LONG setting may be needed if your system or
MPI version does not recognize "long long" data types. In this case a
"long" data type is likely already 64-bits, in which case this setting
will convert to that data type.
</P>
<P>Using one of the -DPACK_ARRAY, -DPACK_POINTER, and -DPACK_MEMCPY
options can make for faster parallel FFTs (in the PPPM solver) on some
platforms. The -DPACK_ARRAY setting is the default. See the
<A HREF = "kspace_style.html">kspace_style</A> command for info about PPPM. See
Step 6 below for info about building LAMMPS with an FFT library.
</P>
<P><B>Step 5</B>
</P>
<P>The 3 MPI variables are used to specify an MPI library to build LAMMPS
with.
</P>
<P>If you want LAMMPS to run in parallel, you must have an MPI library
installed on your platform. If you use an MPI-wrapped compiler, such
as "mpicc" to build LAMMPS, you should be able to leave these 3
variables blank; the MPI wrapper knows where to find the needed files.
If not, and MPI is installed on your system in the usual place (under
/usr/local), you also may not need to specify these 3 variables. On
some large parallel machines which use "modules" for their
compile/link environements, you may simply need to include the correct
module in your build environment. Or the parallel machine may have a
vendor-provided MPI which the compiler has no trouble finding.
</P>
<P>Failing this, with these 3 variables you can specify where the mpi.h
file (MPI_INC) and the MPI library file (MPI_PATH) are found and the
name of the library file (MPI_LIB).
</P>
<P>If you are installing MPI yourself, we recommend Argonne's MPICH2
or OpenMPI. MPICH can be downloaded from the <A HREF = "http://www.mcs.anl.gov/research/projects/mpich2/">Argonne MPI
site</A>. OpenMPI can
be downloaded from the <A HREF = "http://www.open-mpi.org">OpenMPI site</A>.
Other MPI packages should also work. If you are running on a big
parallel platform, your system people or the vendor should have
already installed a version of MPI, which is likely to be faster
than a self-installed MPICH or OpenMPI, so find out how to build
and link with it. If you use MPICH or OpenMPI, you will have to
configure and build it for your platform. The MPI configure script
should have compiler options to enable you to use the same compiler
you are using for the LAMMPS build, which can avoid problems that can
arise when linking LAMMPS to the MPI library.
</P>
<P>If you just want to run LAMMPS on a single processor, you can use the
dummy MPI library provided in src/STUBS, since you don't need a true
MPI library installed on your system. See the
src/MAKE/Makefile.serial file for how to specify the 3 MPI variables
in this case. You will also need to build the STUBS library for your
platform before making LAMMPS itself. To build from the src
directory, type "make stubs", or from the STUBS dir, type "make".
This should create a libmpi_stubs.a file suitable for linking to
LAMMPS. If the build fails, you will need to edit the STUBS/Makefile
for your platform.
</P>
<P>The file STUBS/mpi.c provides a CPU timer function called
MPI_Wtime() that calls gettimeofday() . If your system doesn't
support gettimeofday() , you'll need to insert code to call another
timer. Note that the ANSI-standard function clock() rolls over after
an hour or so, and is therefore insufficient for timing long LAMMPS
simulations.
</P>
<P><B>Step 6</B>
</P>
<P>The 3 FFT variables allow you to specify an FFT library which LAMMPS
uses (for performing 1d FFTs) when running the particle-particle
particle-mesh (PPPM) option for long-range Coulombics via the
<A HREF = "kspace_style.html">kspace_style</A> command.
</P>
<P>LAMMPS supports various open-source or vendor-supplied FFT libraries
for this purpose. If you leave these 3 variables blank, LAMMPS will
use the open-source <A HREF = "http://kissfft.sf.net">KISS FFT library</A>, which is
included in the LAMMPS distribution. This library is portable to all
platforms and for typical LAMMPS simulations is almost as fast as FFTW
or vendor optimized libraries. If you are not including the KSPACE
package in your build, you can also leave the 3 variables blank.
</P>
<P>Otherwise, select which kinds of FFTs to use as part of the FFT_INC
setting by a switch of the form -DFFT_XXX. Recommended values for XXX
are: MKL, SCSL, FFTW2, and FFTW3. Legacy options are: INTEL, SGI,
ACML, and T3E. For backward compatability, using -DFFT_FFTW will use
the FFTW2 library. Using -DFFT_NONE will use the KISS library
described above.
</P>
<P>You may also need to set the FFT_INC, FFT_PATH, and FFT_LIB variables,
so the compiler and linker can find the needed FFT header and library
files. Note that on some large parallel machines which use "modules"
for their compile/link environements, you may simply need to include
the correct module in your build environment. Or the parallel machine
may have a vendor-provided FFT library which the compiler has no
trouble finding.
</P>
<P>FFTW is a fast, portable library that should also work on any
platform. You can download it from
<A HREF = "http://www.fftw.org">www.fftw.org</A>. Both the legacy version 2.1.X and
the newer 3.X versions are supported as -DFFT_FFTW2 or -DFFT_FFTW3.
Building FFTW for your box should be as simple as ./configure; make.
Note that on some platforms FFTW2 has been pre-installed, and uses
renamed files indicating the precision it was compiled with,
e.g. sfftw.h, or dfftw.h instead of fftw.h. In this case, you can
specify an additional define variable for FFT_INC called -DFFTW_SIZE,
which will select the correct include file. In this case, for FFT_LIB
you must also manually specify the correct library, namely -lsfftw or
-ldfftw.
</P>
<P>The FFT_INC variable also allows for a -DFFT_SINGLE setting that will
use single-precision FFTs with PPPM, which can speed-up long-range
calulations, particularly in parallel or on GPUs. Fourier transform
and related PPPM operations are somewhat insensitive to floating point
truncation errors and thus do not always need to be performed in
double precision. Using the -DFFT_SINGLE setting trades off a little
accuracy for reduced memory use and parallel communication costs for
transposing 3d FFT data. Note that single precision FFTs have only
been tested with the FFTW3, FFTW2, MKL, and KISS FFT options.
</P>
<P><B>Step 7</B>
</P>
<P>The 3 JPG variables allow you to specify a JPEG and/or PNG library
which LAMMPS uses when writing out JPEG or PNG files via the <A HREF = "dump_image.html">dump
image</A> command. These can be left blank if you do not
use the -DLAMMPS_JPEG or -DLAMMPS_PNG switches discussed above in Step
4, since in that case JPEG/PNG output will be disabled.
</P>
<P>A standard JPEG library usually goes by the name libjpeg.a or
libjpeg.so and has an associated header file jpeglib.h. Whichever
JPEG library you have on your platform, you'll need to set the
appropriate JPG_INC, JPG_PATH, and JPG_LIB variables, so that the
compiler and linker can find it.
</P>
<P>A standard PNG library usually goes by the name libpng.a or libpng.so
and has an associated header file png.h. Whichever PNG library you
have on your platform, you'll need to set the appropriate JPG_INC,
JPG_PATH, and JPG_LIB variables, so that the compiler and linker can
find it.
</P>
<P>As before, if these header and library files are in the usual place on
your machine, you may not need to set these variables.
</P>
<P><B>Step 8</B>
</P>
<P>Note that by default only a few of LAMMPS optional packages are
installed. To build LAMMPS with optional packages, see <A HREF = "#start_3">this
section</A> below, before proceeding to Step 9.
</P>
<P><B>Step 9</B>
</P>
<P>That's it. Once you have a correct Makefile.foo, you have installed
the optional LAMMPS packages you want to include in your build, and
you have pre-built any other needed libraries (e.g. MPI, FFT, package
libraries), all you need to do from the src directory is type
something like this:
</P>
<PRE>make foo
or
gmake foo
</PRE>
<P>You should get the executable lmp_foo when the build is complete.
</P>
<HR>
<A NAME = "start_2_3"></A><B><I>Errors that can occur when making LAMMPS:</I></B>
<P>IMPORTANT NOTE: If an error occurs when building LAMMPS, the compiler
or linker will state very explicitly what the problem is. The error
message should give you a hint as to which of the steps above has
failed, and what you need to do in order to fix it. Building a code
with a Makefile is a very logical process. The compiler and linker
need to find the appropriate files and those files need to be
compatible with LAMMPS source files. When a make fails, there is
usually a very simple reason, which you or a local expert will need to
fix.
</P>
<P>Here are two non-obvious errors that can occur:
</P>
<P>(1) If the make command breaks immediately with errors that indicate
it can't find files with a "*" in their names, this can be because
your machine's native make doesn't support wildcard expansion in a
makefile. Try gmake instead of make. If that doesn't work, try using
a -f switch with your make command to use a pre-generated
Makefile.list which explicitly lists all the needed files, e.g.
</P>
<PRE>make makelist
make -f Makefile.list linux
gmake -f Makefile.list mac
</PRE>
<P>The first "make" command will create a current Makefile.list with all
the file names in your src dir. The 2nd "make" command (make or
gmake) will use it to build LAMMPS. Note that you should
include/exclude any desired optional packages before using the "make
makelist" command.
</P>
<P>(2) If you get an error that says something like 'identifier "atoll"
is undefined', then your machine does not support "long long"
integers. Try using the -DLAMMPS_LONGLONG_TO_LONG setting described
above in Step 4.
</P>
<HR>
<A NAME = "start_2_4"></A><B><I>Additional build tips:</I></B>
<P>(1) Building LAMMPS for multiple platforms.
</P>
<P>You can make LAMMPS for multiple platforms from the same src
directory. Each target creates its own object sub-directory called
Obj_target where it stores the system-specific *.o files.
</P>
<P>(2) Cleaning up.
</P>
<P>Typing "make clean-all" or "make clean-machine" will delete *.o object
files created when LAMMPS is built, for either all builds or for a
particular machine.
</P>
<P>(3) Changing the LAMMPS size limits via -DLAMMPS_SMALLBIG or
-DLAMMPS_BIGBIG or -DLAMMPS_SMALLSMALL
</P>
<P>As explained above, any of these 3 settings can be specified on the
LMP_INC line in your low-level src/MAKE/Makefile.foo.
</P>
<P>The default is -DLAMMPS_SMALLBIG which allows for systems with up to
2^63 atoms and 2^63 timesteps (about 9e18). The atom limit is for
atomic systems which do not store bond topology info and thus do not
require atom IDs. If you use atom IDs for atomic systems (which is
the default) or if you use a molecular model, which stores bond
topology info and thus requires atom IDs, the limit is 2^31 atoms
(about 2 billion). This is because the IDs are stored in 32-bit
integers.
</P>
<P>Likewise, with this setting, the 3 image flags for each atom (see the
<A HREF = "dump.html">dump</A> doc page for a discussion) are stored in a 32-bit
integer, which means the atoms can only wrap around a periodic box (in
each dimension) at most 512 times. If atoms move through the periodic
box more than this many times, the image flags will "roll over",
e.g. from 511 to -512, which can cause diagnostics like the
mean-squared displacement, as calculated by the <A HREF = "compute_msd.html">compute
msd</A> command, to be faulty.
</P>
<P>To allow for larger atomic systems with atom IDs or larger molecular
systems or larger image flags, compile with -DLAMMPS_BIGBIG. This
stores atom IDs and image flags in 64-bit integers. This enables
atomic or molecular systems with atom IDS of up to 2^63 atoms (about
9e18). And image flags will not "roll over" until they reach 2^20 =
1048576.
</P>
<P>If your system does not support 8-byte integers, you will need to
compile with the -DLAMMPS_SMALLSMALL setting. This will restrict the
total number of atoms (for atomic or molecular systems) and timesteps
to 2^31 (about 2 billion). Image flags will roll over at 2^9 = 512.
</P>
<P>Note that in src/lmptype.h there are definitions of all these data
types as well as the MPI data types associated with them. The MPI
types need to be consistent with the associated C data types, or else
LAMMPS will generate a run-time error. As far as we know, the
settings defined in src/lmptype.h are portable and work on every
current system.
</P>
<P>In all cases, the size of problem that can be run on a per-processor
basis is limited by 4-byte integer storage to 2^31 atoms per processor
(about 2 billion). This should not normally be a limitation since such
a problem would have a huge per-processor memory footprint due to
neighbor lists and would run very slowly in terms of CPU secs/timestep.
</P>
<HR>
<A NAME = "start_2_5"></A><B><I>Building for a Mac:</I></B>
<P>OS X is BSD Unix, so it should just work. See the
src/MAKE/Makefile.mac file.
</P>
<HR>
<A NAME = "start_2_6"></A><B><I>Building for Windows:</I></B>
<P>The LAMMPS download page has an option to download both a serial and
parallel pre-built Windows executable. See the <A HREF = "#start_6">Running
LAMMPS</A> section for instructions on running these executables
on a Windows box.
</P>
<P>The pre-built executables hosted on the <A HREF = "http://lammps.sandia.gov/download.html">LAMMPS download
page</A> are built with a subset
of the available packages; see the download page for the list. These
are single executable files. No examples or documentation in
included. You will need to download the full source code package to
obtain those.
</P>
<P>As an alternative, you can download "daily builds" (and some older
versions) of the installer packages from
<A HREF = "http://rpm.lammps.org/windows.html">rpm.lammps.org/windows.html</A>.
These executables are built with most optional packages and the
download includes documentation, some tools and most examples.
</P>
<P>If you want a Windows version with specific packages included and
excluded, you can build it yourself.
</P>
<P>One way to do this is install and use cygwin to build LAMMPS with a
standard unix style make program, just as you would on a Linux box;
see src/MAKE/Makefile.cygwin.
</P>
<P>The other way to do this is using Visual Studio and project files.
See the src/WINDOWS directory and its README.txt file for instructions
on both a basic build and a customized build with pacakges you select.
</P>
<HR>
<H4><A NAME = "start_3"></A>2.3 Making LAMMPS with optional packages
</H4>
<P>This section has the following sub-sections:
</P>
<UL><LI><A HREF = "#start_3_1">Package basics</A>
<LI><A HREF = "#start_3_2">Including/excluding packages</A>
<LI><A HREF = "#start_3_3">Packages that require extra libraries</A>
<LI><A HREF = "#start_3_4">Packages that use make variable settings</A>
</UL>
<HR>
<A NAME = "start_3_1"></A><B><I>Package basics:</I></B>
<P>The source code for LAMMPS is structured as a set of core files which
are always included, plus optional packages. Packages are groups of
files that enable a specific set of features. For example, force
fields for molecular systems or granular systems are in packages. You
can see the list of all packages by typing "make package" from within
the src directory of the LAMMPS distribution.
</P>
<P>If you use a command in a LAMMPS input script that is specific to a
particular package, you must have built LAMMPS with that package, else
you will get an error that the style is invalid or the command is
unknown. Every command's doc page specfies if it is part of a
package. You can also type
</P>
<PRE>lmp_machine -h
</PRE>
<P>to run your executable with the optional <A HREF = "#start_7">-h command-line
switch</A> for "help", which will list the styles and commands
known to your executable.
</P>
<P>There are two kinds of packages in LAMMPS, standard and user packages.
More information about the contents of standard and user packages is
given in <A HREF = "Section_packages.html">Section_packages</A> of the manual. The
difference between standard and user packages is as follows:
</P>
<P>Standard packages are supported by the LAMMPS developers and are
written in a syntax and style consistent with the rest of LAMMPS.
This means we will answer questions about them, debug and fix them if
necessary, and keep them compatible with future changes to LAMMPS.
</P>
<P>User packages have been contributed by users, and always begin with
the user prefix. If they are a single command (single file), they are
typically in the user-misc package. Otherwise, they are a a set of
files grouped together which add a specific functionality to the code.
</P>
<P>User packages don't necessarily meet the requirements of the standard
packages. If you have problems using a feature provided in a user
package, you will likely need to contact the contributor directly to
get help. Information on how to submit additions you make to LAMMPS
as a user-contributed package is given in <A HREF = "Section_modify.html#mod_15">this
section</A> of the documentation.
</P>
<P>Some packages (both standard and user) require additional libraries.
See more details below.
</P>
<HR>
<A NAME = "start_3_2"></A><B><I>Including/excluding packages:</I></B>
<P>To use or not use a package you must include or exclude it before
building LAMMPS. From the src directory, this is typically as simple
as:
</P>
<PRE>make yes-colloid
make g++
</PRE>
<P>or
</P>
<PRE>make no-manybody
make g++
</PRE>
<P>IMPORTANT NOTE: You should NOT include/exclude packages and build
LAMMPS in a single make command by using multiple targets, e.g. make
yes-colloid g++. This is because the make procedure creates a list of
source files that will be out-of-date for the build if the package
configuration changes during the same command.
</P>
<P>Some packages have individual files that depend on other packages
being included. LAMMPS checks for this and does the right thing.
I.e. individual files are only included if their dependencies are
already included. Likewise, if a package is excluded, other files
dependent on that package are also excluded.
</P>
<P>The reason to exclude packages is if you will never run certain kinds
of simulations. For some packages, this will keep you from having to
build auxiliary libraries (see below), and will also produce a smaller
executable which may run a bit faster.
</P>
<P>When you download a LAMMPS tarball, these packages are pre-installed
in the src directory: KSPACE, MANYBODY,MOLECULE. When you download
LAMMPS source files from the SVN or Git repositories, no packages are
pre-installed.
</P>
<P>Packages are included or excluded by typing "make yes-name" or "make
no-name", where "name" is the name of the package in lower-case, e.g.
name = kspace for the KSPACE package or name = user-atc for the
USER-ATC package. You can also type "make yes-standard", "make
no-standard", "make yes-user", "make no-user", "make yes-all" or "make
no-all" to include/exclude various sets of packages. Type "make
package" to see the all of the package-related make options.
</P>
<P>IMPORTANT NOTE: Inclusion/exclusion of a package works by simply
moving files back and forth between the main src directory and
sub-directories with the package name (e.g. src/KSPACE, src/USER-ATC),
so that the files are seen or not seen when LAMMPS is built. After
you have included or excluded a package, you must re-build LAMMPS.
</P>
<P>Additional package-related make options exist to help manage LAMMPS
files that exist in both the src directory and in package
sub-directories. You do not normally need to use these commands
unless you are editing LAMMPS files or have downloaded a patch from
the LAMMPS WWW site.
</P>
<P>Typing "make package-update" will overwrite src files with files from
the package sub-directories if the package has been included. It
should be used after a patch is installed, since patches only update
the files in the package sub-directory, but not the src files. Typing
"make package-overwrite" will overwrite files in the package
sub-directories with src files.
</P>
<P>Typing "make package-status" will show which packages are currently
included. Of those that are included, it will list files that are
different in the src directory and package sub-directory. Typing
"make package-diff" lists all differences between these files. Again,
type "make package" to see all of the package-related make options.
</P>
<HR>
<A NAME = "start_3_3"></A><B><I>Packages that require extra libraries:</I></B>
<P>A few of the standard and user packages require additional auxiliary
libraries. They must be compiled first, before LAMMPS is built. If
you get a LAMMPS build error about a missing library, this is likely
the reason. See the <A HREF = "Section_packages.html">Section_packages</A> doc page
for a list of packages that have auxiliary libraries.
</P>
<P>Code for some of these auxiliary libraries is included in the LAMMPS
distribution under the lib directory. Examples are the USER-ATC and
MEAM packages. Some auxiliary libraries are NOT included with LAMMPS;
to use the associated package you must download and install the
auxiliary library yourself. Examples are the KIM and VORONOI and
USER-MOLFILE packages.
</P>
<P>For libraries with provided source code, each lib directory has a
README file (e.g. lib/reax/README) with instructions on how to build
that library. Typically this is done by typing something like:
</P>
<PRE>make -f Makefile.g++
</PRE>
<P>If one of the provided Makefiles is not appropriate for your system
you will need to edit or add one. Note that all the Makefiles have a
setting for EXTRAMAKE at the top that specifies a Makefile.lammps.*
file.
</P>
<P>If the library build is successful, it will produce 2 files in the lib
directory:
</P>
<PRE>libpackage.a
Makefile.lammps
</PRE>
<P>The Makefile.lammps file will be a copy of the EXTRAMAKE file setting
specified in the library Makefile.* you used.
</P>
<P>Note that you must insure that the settings in Makefile.lammps are
appropriate for your system. If they are not, the LAMMPS build will
fail.
</P>
<P>As explained in the lib/package/README files, the settings in
Makefile.lammps are used to specify additional system libraries and
their locations so that LAMMPS can build with the auxiliary library.
For example, if the MEAM or REAX packages are used, the auxiliary
libraries consist of F90 code, built with a Fortran complier. To link
that library with LAMMPS (a C++ code) via whatever C++ compiler LAMMPS
is built with, typically requires additional Fortran-to-C libraries be
included in the link. Another example are the BLAS and LAPACK
libraries needed to use the USER-ATC or USER-AWPMD packages.
</P>
<P>For libraries without provided source code, see the
src/package/Makefile.lammps file for information on where to find the
library and how to build it. E.g. the file src/KIM/Makefile.lammps or
src/VORONOI/Makefile.lammps or src/UESR-MOLFILE/Makefile.lammps.
These files serve the same purpose as the lib/package/Makefile.lammps
files described above. The files have settings needed when LAMMPS is
built to link with the corresponding auxiliary library.
</P>
<P>Again, you must insure that the settings in
src/package/Makefile.lammps are appropriate for your system and where
you installed the auxiliary library. If they are not, the LAMMPS
build will fail.
</P>
<HR>
<A NAME = "start_3_4"></A><B><I>Packages that use make variable settings</I></B>
<P>One package, the KOKKOS package, allows its build options to be
specified by setting variables via the "make" command, rather than by
first building an auxiliary library and editing a Makefile.lammps
file, as discussed in the previous sub-section for other packages.
This is for convenience since it is common to want to experiment with
different Kokkos library options. Using variables enables a direct
re-build of LAMMPS and its Kokkos dependencies, so that a benchmark
test with different Kokkos options can be quickly performed.
</P>
<P>The syntax for setting make variables is as follows. You must
use a GNU-compatible make command for this to work. Try "gmake"
if your system's standard make complains.
</P>
<PRE>make yes-kokkos
make g++ VAR1=value VAR2=value ...
</PRE>
<P>The first line installs the KOKKOS package, which only needs to be
done once. The second line builds LAMMPS with src/MAKE/Makefile.g++
and optionally sets one or more variables that affect the build. Each
variable is specified in upper-case; its value follows an equal sign
with no spaces. The second line can be repeated with different
variable settings, though a "clean" must be done before the rebuild.
Type "make clean" to see options for this operation.
</P>
<P>These are the variables that can be specified. Each takes a value of
<I>yes</I> or <I>no</I>. The default value is listed, which is set in the
lib/kokkos/Makefile.lammps file. See <A HREF = "Section_accelerate.html#acc_8">this
section</A> for a discussion of what is
meant by "host" and "device" in the Kokkos context.
</P>
<UL><LI>OMP, default = <I>yes</I>
<LI>CUDA, default = <I>no</I>
<LI>HWLOC, default = <I>no</I>
<LI>AVX, default = <I>no</I>
<LI>MIC, default = <I>no</I>
<LI>LIBRT, default = <I>no</I>
<LI>DEBUG, default = <I>no</I>
</UL>
<P>OMP sets the parallelization method used for Kokkos code (within
LAMMPS) that runs on the host. OMP=yes means that OpenMP will be
used. OMP=no means that pthreads will be used.
</P>
<P>CUDA sets the parallelization method used for Kokkos code (within
LAMMPS) that runs on the device. CUDA=yes means an NVIDIA GPU running
CUDA will be used. CUDA=no means that the OMP=yes or OMP=no setting
will be used for the device as well as the host.
</P>
<P>If CUDA=yes, then the lo-level Makefile in the src/MAKE directory must
use "nvcc" as its compiler, via its CC setting. For best performance
its CCFLAGS setting should use -O3 and have an -arch setting that
matches the compute capability of your NVIDIA hardware and software
installation, e.g. -arch=sm_20. Generally Fermi Generation GPUs are
sm_20, while Kepler generation GPUs are sm_30 or sm_35 and Maxwell
cards are sm_50. A complete list can be found on
<A HREF = "http://en.wikipedia.org/wiki/CUDA#Supported_GPUs">wikipedia</A>. You can
also use the deviceQuery tool that comes with the CUDA samples. Note
the minimal required compute capability is 2.0, but this will give
signicantly reduced performance compared to Kepler generation GPUs
with compute capability 3.x. For the LINK setting, "nvcc" should not
be used; instead use g++ or another compiler suitable for linking C++
applications. Often you will want to use your MPI compiler wrapper
for this setting (i.e. mpicxx). Finally, the lo-level Makefile must
also have a "Compilation rule" for creating *.o files from *.cu files.
See src/Makefile.cuda for an example of a lo-level Makefile with all
of these settings.
</P>
<P>HWLOC binds threads to hardware cores, so they do not migrate during a
simulation. HWLOC=yes should always be used if running with OMP=no
for pthreads. It is not necessary for OMP=yes for OpenMP, because
OpenMP provides alternative methods via environment variables for
binding threads to hardware cores. More info on binding threads to
cores is given in <A HREF = "Section_accelerate.html#acc_8">this section</A>.
</P>
<P>AVX enables Intel advanced vector extensions when compiling for an
Intel-compatible chip. AVX=yes should only be set if your host
hardware supports AVX. If it does not support it, this will cause a
run-time crash.
</P>
<P>MIC enables compiler switches needed when compling for an Intel Phi
processor.
</P>
<P>LIBRT enables use of a more accurate timer mechanism on most Unix
platforms. This library is not available on all platforms.
</P>
<P>DEBUG is only useful when developing a Kokkos-enabled style within
LAMMPS. DEBUG=yes enables printing of run-time debugging information
that can be useful. It also enables runtime bounds checking on Kokkos
data structures.
</P>
<HR>
<H4><A NAME = "start_4"></A>2.4 Building LAMMPS via the Make.py script
</H4>
<P>The src directory includes a Make.py script, written
in Python, which can be used to automate various steps
of the build process.
</P>
<P>You can run the script from the src directory by typing either:
</P>
<PRE>Make.py
python Make.py
</PRE>
<P>which will give you info about the tool. For the former to work, you
may need to edit the 1st line of the script to point to your local
Python. And you may need to insure the script is executable:
</P>
<PRE>chmod +x Make.py
</PRE>
<P>The following options are supported as switches:
</P>
<UL><LI>-i file1 file2 ...
<LI>-p package1 package2 ...
<LI>-u package1 package2 ...
<LI>-e package1 arg1 arg2 package2 ...
<LI>-o dir
<LI>-b machine
<LI>-s suffix1 suffix2 ...
<LI>-l dir
<LI>-j N
<LI>-h switch1 switch2 ...
</UL>
<P>Help on any switch can be listed by using -h, e.g.
</P>
<PRE>Make.py -h -i -p
</PRE>
<P>At a hi-level, these are the kinds of package management
and build tasks that can be performed easily, using
the Make.py tool:
</P>
<UL><LI>install/uninstall packages and build the associated external libs (use -p and -u and -e)
<LI>install packages needed for one or more input scripts (use -i and -p)
<LI>build LAMMPS, either in the src dir or new dir (use -b)
<LI>create a new dir with only the source code needed for one or more input scripts (use -i and -o)
</UL>
<P>The last bullet can be useful when you wish to build a stripped-down
version of LAMMPS to run a specific script(s). Or when you wish to
move the minimal amount of files to another platform for a remote
LAMMPS build.
</P>
<P>Note that using Make.py is not a substitute for insuring you have a
valid src/MAKE/Makefile.foo for your system, or that external library
Makefiles in any lib/* directories you use are also valid for your
system. But once you have done that, you can use Make.py to quickly
include/exclude the packages and external libraries needed by your
input scripts.
</P>
<HR>
<H4><A NAME = "start_5"></A>2.5 Building LAMMPS as a library
</H4>
<P>LAMMPS can be built as either a static or shared library, which can
then be called from another application or a scripting language. See
<A HREF = "Section_howto.html#howto_10">this section</A> for more info on coupling
LAMMPS to other codes. See <A HREF = "Section_python.html">this section</A> for
more info on wrapping and running LAMMPS from Python.
</P>
<H5><B>Static library:</B>
</H5>
<P>To build LAMMPS as a static library (*.a file on Linux), type
</P>
<PRE>make makelib
make -f Makefile.lib foo
</PRE>
<P>where foo is the machine name. This kind of library is typically used
to statically link a driver application to LAMMPS, so that you can
insure all dependencies are satisfied at compile time. Note that
inclusion or exclusion of any desired optional packages should be done
before typing "make makelib". The first "make" command will create a
current Makefile.lib with all the file names in your src dir. The
second "make" command will use it to build LAMMPS as a static library,
using the ARCHIVE and ARFLAGS settings in src/MAKE/Makefile.foo. The
build will create the file liblammps_foo.a which another application can
link to.
</P>
<H5><B>Shared library:</B>
</H5>
<P>To build LAMMPS as a shared library (*.so file on Linux), which can be
dynamically loaded, e.g. from Python, type
</P>
<PRE>make makeshlib
make -f Makefile.shlib foo
</PRE>
<P>where foo is the machine name. This kind of library is required when
wrapping LAMMPS with Python; see <A HREF = "Section_python.html">Section_python</A>
for details. Again, note that inclusion or exclusion of any desired
optional packages should be done before typing "make makelib". The
first "make" command will create a current Makefile.shlib with all the
file names in your src dir. The second "make" command will use it to
build LAMMPS as a shared library, using the SHFLAGS and SHLIBFLAGS
settings in src/MAKE/Makefile.foo. The build will create the file
liblammps_foo.so which another application can link to dyamically. It
will also create a soft link liblammps.so, which the Python wrapper uses
by default.
</P>
<P>Note that for a shared library to be usable by a calling program, all
the auxiliary libraries it depends on must also exist as shared
libraries. This will be the case for libraries included with LAMMPS,
such as the dummy MPI library in src/STUBS or any package libraries in
lib/packges, since they are always built as shared libraries with the
-fPIC switch. However, if a library like MPI or FFTW does not exist
as a shared library, the second make command will generate an error.
This means you will need to install a shared library version of the
package. The build instructions for the library should tell you how
to do this.
</P>
<P>As an example, here is how to build and install the <A HREF = "http://www-unix.mcs.anl.gov/mpi">MPICH
library</A>, a popular open-source version of MPI, distributed by
Argonne National Labs, as a shared library in the default
/usr/local/lib location:
</P>
<PRE>./configure --enable-shared
make
make install
</PRE>
<P>You may need to use "sudo make install" in place of the last line if
you do not have write privileges for /usr/local/lib. The end result
should be the file /usr/local/lib/libmpich.so.
</P>
<H5><B>Additional requirement for using a shared library:</B>
</H5>
<P>The operating system finds shared libraries to load at run-time using
the environment variable LD_LIBRARY_PATH. So you may wish to copy the
file src/liblammps.so or src/liblammps_g++.so (for example) to a place
the system can find it by default, such as /usr/local/lib, or you may
wish to add the LAMMPS src directory to LD_LIBRARY_PATH, so that the
current version of the shared library is always available to programs
that use it.
</P>
<P>For the csh or tcsh shells, you would add something like this to your
~/.cshrc file:
</P>
<PRE>setenv LD_LIBRARY_PATH $<I>LD_LIBRARY_PATH</I>:/home/sjplimp/lammps/src
</PRE>
<H5><B>Calling the LAMMPS library:</B>
</H5>
<P>Either flavor of library (static or shared0 allows one or more LAMMPS
objects to be instantiated from the calling program.
</P>
<P>When used from a C++ program, all of LAMMPS is wrapped in a LAMMPS_NS
namespace; you can safely use any of its classes and methods from
within the calling code, as needed.
</P>
<P>When used from a C or Fortran program or a scripting language like
Python, the library has a simple function-style interface, provided in
src/library.cpp and src/library.h.
</P>
<P>See the sample codes in examples/COUPLE/simple for examples of C++ and
C and Fortran codes that invoke LAMMPS thru its library interface.
There are other examples as well in the COUPLE directory which are
discussed in <A HREF = "Section_howto.html#howto_10">Section_howto 10</A> of the
manual. See <A HREF = "Section_python.html">Section_python</A> of the manual for a
description of the Python wrapper provided with LAMMPS that operates
through the LAMMPS library interface.
</P>
<P>The files src/library.cpp and library.h define the C-style API for
using LAMMPS as a library. See <A HREF = "Section_howto.html#howto_19">Section_howto
19</A> of the manual for a description of the
interface and how to extend it for your needs.
</P>
<HR>
<H4><A NAME = "start_6"></A>2.6 Running LAMMPS
</H4>
<P>By default, LAMMPS runs by reading commands from standard input. Thus
if you run the LAMMPS executable by itself, e.g.
</P>
<PRE>lmp_linux
</PRE>
<P>it will simply wait, expecting commands from the keyboard. Typically
you should put commands in an input script and use I/O redirection,
e.g.
</P>
<PRE>lmp_linux < in.file
</PRE>
<P>For parallel environments this should also work. If it does not, use
the '-in' command-line switch, e.g.
</P>
<PRE>lmp_linux -in in.file
</PRE>
<P><A HREF = "Section_commands.html">This section</A> describes how input scripts are
structured and what commands they contain.
</P>
<P>You can test LAMMPS on any of the sample inputs provided in the
examples or bench directory. Input scripts are named in.* and sample
outputs are named log.*.name.P where name is a machine and P is the
number of processors it was run on.
</P>
<P>Here is how you might run a standard Lennard-Jones benchmark on a
Linux box, using mpirun to launch a parallel job:
</P>
<PRE>cd src
make linux
cp lmp_linux ../bench
cd ../bench
mpirun -np 4 lmp_linux < in.lj
</PRE>
<P>See <A HREF = "http://lammps.sandia.gov/bench.html">this page</A> for timings for this and the other benchmarks on
various platforms. Note that some of the example scripts require
LAMMPS to be built with one or more of its optional packages.
</P>
<HR>
<P>On a Windows box, you can skip making LAMMPS and simply download an
executable, as described above, though the pre-packaged executables
include only certain packages.
</P>
<P>To run a LAMMPS executable on a Windows machine, first decide whether
you want to download the non-MPI (serial) or the MPI (parallel)
version of the executable. Download and save the version you have
chosen.
</P>
<P>For the non-MPI version, follow these steps:
</P>
<UL><LI>Get a command prompt by going to Start->Run... ,
then typing "cmd".
<LI>Move to the directory where you have saved lmp_win_no-mpi.exe
(e.g. by typing: cd "Documents").
<LI>At the command prompt, type "lmp_win_no-mpi -in in.lj", replacing in.lj
with the name of your LAMMPS input script.
</UL>
<P>For the MPI version, which allows you to run LAMMPS under Windows on
multiple processors, follow these steps:
</P>
<UL><LI>Download and install
<A HREF = "http://www.mcs.anl.gov/research/projects/mpich2/downloads/index.php?s=downloads">MPICH2</A>
for Windows.
<LI>You'll need to use the mpiexec.exe and smpd.exe files from the MPICH2
package. Put them in same directory (or path) as the LAMMPS Windows
executable.
<LI>Get a command prompt by going to Start->Run... ,
then typing "cmd".
<LI>Move to the directory where you have saved lmp_win_mpi.exe
(e.g. by typing: cd "Documents").
<LI>Then type something like this: "mpiexec -localonly 4 lmp_win_mpi -in
in.lj", replacing in.lj with the name of your LAMMPS input script.
<LI>Note that you may need to provide smpd with a passphrase (it doesn't
matter what you type).
<LI>In this mode, output may not immediately show up on the screen, so if
your input script takes a long time to execute, you may need to be
patient before the output shows up. :l Alternatively, you can still
use this executable to run on a single processor by typing something
like: "lmp_win_mpi -in in.lj".
</UL>
<HR>
<P>The screen output from LAMMPS is described in the next section. As it
runs, LAMMPS also writes a log.lammps file with the same information.
</P>
<P>Note that this sequence of commands copies the LAMMPS executable
(lmp_linux) to the directory with the input files. This may not be
necessary, but some versions of MPI reset the working directory to
where the executable is, rather than leave it as the directory where
you launch mpirun from (if you launch lmp_linux on its own and not
under mpirun). If that happens, LAMMPS will look for additional input
files and write its output files to the executable directory, rather
than your working directory, which is probably not what you want.
</P>
<P>If LAMMPS encounters errors in the input script or while running a
simulation it will print an ERROR message and stop or a WARNING
message and continue. See <A HREF = "Section_errors.html">Section_errors</A> for a
discussion of the various kinds of errors LAMMPS can or can't detect,
a list of all ERROR and WARNING messages, and what to do about them.
</P>
<P>LAMMPS can run a problem on any number of processors, including a
single processor. In theory you should get identical answers on any
number of processors and on any machine. In practice, numerical
round-off can cause slight differences and eventual divergence of
molecular dynamics phase space trajectories.
</P>
<P>LAMMPS can run as large a problem as will fit in the physical memory
of one or more processors. If you run out of memory, you must run on
more processors or setup a smaller problem.
</P>
<HR>
<H4><A NAME = "start_7"></A>2.7 Command-line options
</H4>
<P>At run time, LAMMPS recognizes several optional command-line switches
which may be used in any order. Either the full word or a one-or-two
letter abbreviation can be used:
</P>
<UL><LI>-c or -cuda
<LI>-e or -echo
<LI>-i or -in
<LI>-h or -help
<LI>-k or -kokkos
<LI>-l or -log
<LI>-nc or -nocite
<LI>-p or -partition
<LI>-pl or -plog
<LI>-ps or -pscreen
<LI>-r or -restart
<LI>-ro or -reorder
<LI>-sc or -screen
<LI>-sf or -suffix
<LI>-v or -var
</UL>
<P>For example, lmp_ibm might be launched as follows:
</P>
<PRE>mpirun -np 16 lmp_ibm -v f tmp.out -l my.log -sc none < in.alloy
mpirun -np 16 lmp_ibm -var f tmp.out -log my.log -screen none < in.alloy
</PRE>
<P>Here are the details on the options:
</P>
<PRE>-cuda on/off
</PRE>
<P>Explicitly enable or disable CUDA support, as provided by the
USER-CUDA package. Even if LAMMPS is built with this package, as
described above in <A HREF = "#start_3">Section 2.3</A>, this switch must be set to
enable running with the CUDA-enabled styles the package provides. If
the switch is not set (the default), LAMMPS will operate as if the
USER-CUDA package were not installed; i.e. you can run standard LAMMPS
or with the GPU package, for testing or benchmarking purposes.
</P>
<PRE>-echo style
</PRE>
<P>Set the style of command echoing. The style can be <I>none</I> or <I>screen</I>
or <I>log</I> or <I>both</I>. Depending on the style, each command read from
the input script will be echoed to the screen and/or logfile. This
can be useful to figure out which line of your script is causing an
input error. The default value is <I>log</I>. The echo style can also be
set by using the <A HREF = "echo.html">echo</A> command in the input script itself.
</P>
<PRE>-in file
</PRE>
<P>Specify a file to use as an input script. This is an optional switch
when running LAMMPS in one-partition mode. If it is not specified,
LAMMPS reads its script from standard input, typically from a script
via I/O redirection; e.g. lmp_linux < in.run. I/O redirection should
also work in parallel, but if it does not (in the unlikely case that
an MPI implementation does not support it), then use the -in flag.
Note that this is a required switch when running LAMMPS in
multi-partition mode, since multiple processors cannot all read from
stdin.
</P>
<PRE>-help
</PRE>
<P>Print a brief help summary and a list of options compiled into this
executable for each LAMMPS style (atom_style, fix, compute,
pair_style, bond_style, etc). This can tell you if the command you
want to use was included via the appropriate package at compile time.
LAMMPS will print the info and immediately exit if this switch is
used.
</P>
<PRE>-kokkos on/off keyword/value ...
</PRE>
<P>Explicitly enable or disable KOKKOS support, as provided by the KOKKOS
package. Even if LAMMPS is built with this package, as described
above in <A HREF = "#start_3">Section 2.3</A>, this switch must be set to enable
running with the KOKKOS-enabled styles the package provides. If the
switch is not set (the default), LAMMPS will operate as if the KOKKOS
package were not installed; i.e. you can run standard LAMMPS or with
the GPU or USER-CUDA or USER-OMP packages, for testing or benchmarking
purposes.
</P>
<P>Additional optional keyword/value pairs can be specified which
determine how Kokkos will use the underlying hardware on your
platform. These settings apply to each MPI task you launch via the
"mpirun" or "mpiexec" command. You may choose to run one or more MPI
tasks per physical node. Note that if you are running on a desktop
machine, you typically have one physical node. On a cluster or
supercomputer there may be dozens or 1000s of physical nodes.
</P>
<P>Either the full word or an abbreviation can be used for the keywords.
Note that the keywords do not use a leading minus sign. I.e. the
keyword is "t", not "-t". Also note that each of the keywords has a
default setting. Example of when to use these options and what
settings to use on different platforms is given in <A HREF = "Section_accelerate.html#acc_8">Section
5.8</A>.
</P>
<UL><LI>d or device
<LI>g or gpus
<LI>t or threads
<LI>n or numa
</UL>
<PRE>device Nd
</PRE>
<P>This option is only relevant if you built LAMMPS with CUDA=yes, you
have more than one GPU per node, and if you are running with only one
MPI task per node. The Nd setting is the ID of the GPU on the node to
run on. By default Nd = 0. If you have multiple GPUs per node, they
have consecutive IDs numbered as 0,1,2,etc. This setting allows you
to launch multiple independent jobs on the node, each with a single
MPI task per node, and assign each job to run on a different GPU.
</P>
<PRE>gpus Ng Ns
</PRE>
<P>This option is only relevant if you built LAMMPS with CUDA=yes, you
have more than one GPU per node, and you are running with multiple MPI
tasks per node (up to one per GPU). The Ng setting is how many GPUs
you will use. The Ns setting is optional. If set, it is the ID of a
GPU to skip when assigning MPI tasks to GPUs. This may be useful if
your desktop system reserves one GPU to drive the screen and the rest
are intended for computational work like running LAMMPS. By default
Ng = 1 and Ns is not set.
</P>
<P>Depending on which flavor of MPI you are running, LAMMPS will look for
one of these 3 environment variables
</P>
<PRE>SLURM_LOCALID (various MPI variants compiled with SLURM support)
MV2_COMM_WORLD_LOCAL_RANK (Mvapich)
OMPI_COMM_WORLD_LOCAL_RANK (OpenMPI)
</PRE>
<P>which are initialized by the "srun", "mpirun" or "mpiexec" commands.
The environment variable setting for each MPI rank is used to assign a
unique GPU ID to the MPI task.
</P>
<PRE>threads Nt
</PRE>
<P>This option assigns Nt number of threads to each MPI task for
performing work when Kokkos is executing in OpenMP or pthreads mode.
The default is Nt = 1, which essentially runs in MPI-only mode. If
there are Np MPI tasks per physical node, you generally want Np*Nt =
the number of physical cores per node, to use your available hardware
optimally. This also sets the number of threads used by the host when
LAMMPS is compiled with CUDA=yes.
</P>
<PRE>numa Nm
</PRE>
<P>This option is only relevant when using pthreads with hwloc support.
In this case Nm defines the number of NUMA regions (typicaly sockets)
on a node which will be utilizied by a single MPI rank. By default Nm
= 1. If this option is used the total number of worker-threads per
MPI rank is threads*numa. Currently it is always almost better to
assign at least one MPI rank per NUMA region, and leave numa set to
its default value of 1. This is because letting a single process span
multiple NUMA regions induces a significant amount of cross NUMA data
traffic which is slow.
</P>
<PRE>-log file
</PRE>
<P>Specify a log file for LAMMPS to write status information to. In
one-partition mode, if the switch is not used, LAMMPS writes to the
file log.lammps. If this switch is used, LAMMPS writes to the
specified file. In multi-partition mode, if the switch is not used, a
log.lammps file is created with hi-level status information. Each
partition also writes to a log.lammps.N file where N is the partition
ID. If the switch is specified in multi-partition mode, the hi-level
logfile is named "file" and each partition also logs information to a
file.N. For both one-partition and multi-partition mode, if the
specified file is "none", then no log files are created. Using a
<A HREF = "log.html">log</A> command in the input script will override this setting.
Option -plog will override the name of the partition log files file.N.
</P>
<PRE>-nocite
</PRE>
<P>Disable writing the log.cite file which is normally written to list
references for specific cite-able features used during a LAMMPS run.
See the <A HREF = "http://lammps.sandia.gov/cite.html">citation page</A> for more
details.
</P>
<PRE>-partition 8x2 4 5 ...
</PRE>
<P>Invoke LAMMPS in multi-partition mode. When LAMMPS is run on P
processors and this switch is not used, LAMMPS runs in one partition,
i.e. all P processors run a single simulation. If this switch is
used, the P processors are split into separate partitions and each
partition runs its own simulation. The arguments to the switch
specify the number of processors in each partition. Arguments of the
form MxN mean M partitions, each with N processors. Arguments of the
form N mean a single partition with N processors. The sum of
processors in all partitions must equal P. Thus the command
"-partition 8x2 4 5" has 10 partitions and runs on a total of 25
processors.
</P>
<P>Running with multiple partitions can e useful for running
<A HREF = "Section_howto.html#howto_5">multi-replica simulations</A>, where each
replica runs on on one or a few processors. Note that with MPI
installed on a machine (e.g. your desktop), you can run on more
(virtual) processors than you have physical processors.
</P>
<P>To run multiple independent simulatoins from one input script, using
multiple partitions, see <A HREF = "Section_howto.html#howto_4">Section_howto 4</A>
of the manual. World- and universe-style <A HREF = "variable.html">variables</A>
are useful in this context.
</P>
<PRE>-plog file
</PRE>
<P>Specify the base name for the partition log files, so partition N
writes log information to file.N. If file is none, then no partition
log files are created. This overrides the filename specified in the
-log command-line option. This option is useful when working with
large numbers of partitions, allowing the partition log files to be
suppressed (-plog none) or placed in a sub-directory (-plog
replica_files/log.lammps) If this option is not used the log file for
partition N is log.lammps.N or whatever is specified by the -log
command-line option.
</P>
<PRE>-pscreen file
</PRE>
<P>Specify the base name for the partition screen file, so partition N
writes screen information to file.N. If file is none, then no
partition screen files are created. This overrides the filename
specified in the -screen command-line option. This option is useful
when working with large numbers of partitions, allowing the partition
screen files to be suppressed (-pscreen none) or placed in a
sub-directory (-pscreen replica_files/screen). If this option is not
used the screen file for partition N is screen.N or whatever is
specified by the -screen command-line option.
</P>
<PRE>-restart restartfile <I>remap</I> datafile keyword value ...
</PRE>
<P>Convert the restart file into a data file and immediately exit. This
is the same operation as if the following 2-line input script were
run:
</P>
<PRE>read_restart restartfile <I>remap</I>
write_data datafile keyword value ...
</PRE>
<P>Note that the specified restartfile and datafile can have wild-card
characters ("*",%") as described by the
<A HREF = "read_restart.html">read_restart</A> and <A HREF = "write_data.html">write_data</A>
commands. But a filename such as file.* will need to be enclosed in
quotes to avoid shell expansion of the "*" character.
</P>
<P>Note that following restartfile, the optional flag <I>remap</I> can be
used. This has the same effect as adding it to the
<A HREF = "read_restart.html">read_restart</A> command, as explained on its doc
page. This is only useful if the reading of the restart file triggers
an error that atoms have been lost. In that case, use of the remap
flag should allow the data file to still be produced.
</P>
<P>Also note that following datafile, the same optional keyword/value
pairs can be listed as used by the <A HREF = "write_data.html">write_data</A>
command.
</P>
<PRE>-reorder nth N
-reorder custom filename
</PRE>
<P>Reorder the processors in the MPI communicator used to instantiate
LAMMPS, in one of several ways. The original MPI communicator ranks
all P processors from 0 to P-1. The mapping of these ranks to
physical processors is done by MPI before LAMMPS begins. It may be
useful in some cases to alter the rank order. E.g. to insure that
cores within each node are ranked in a desired order. Or when using
the <A HREF = "run_style.html">run_style verlet/split</A> command with 2 partitions
to insure that a specific Kspace processor (in the 2nd partition) is
matched up with a specific set of processors in the 1st partition.
See the <A HREF = "Section_accelerate.html">Section_accelerate</A> doc pages for
more details.
</P>
<P>If the keyword <I>nth</I> is used with a setting <I>N</I>, then it means every
Nth processor will be moved to the end of the ranking. This is useful
when using the <A HREF = "run_style.html">run_style verlet/split</A> command with 2
partitions via the -partition command-line switch. The first set of
processors will be in the first partition, the 2nd set in the 2nd
partition. The -reorder command-line switch can alter this so that
the 1st N procs in the 1st partition and one proc in the 2nd partition
will be ordered consecutively, e.g. as the cores on one physical node.
This can boost performance. For example, if you use "-reorder nth 4"
and "-partition 9 3" and you are running on 12 processors, the
processors will be reordered from
</P>
<PRE>0 1 2 3 4 5 6 7 8 9 10 11
</PRE>
<P>to
</P>
<PRE>0 1 2 4 5 6 8 9 10 3 7 11
</PRE>
<P>so that the processors in each partition will be
</P>
<PRE>0 1 2 4 5 6 8 9 10
3 7 11
</PRE>
<P>See the "processors" command for how to insure processors from each
partition could then be grouped optimally for quad-core nodes.
</P>
<P>If the keyword is <I>custom</I>, then a file that specifies a permutation
of the processor ranks is also specified. The format of the reorder
file is as follows. Any number of initial blank or comment lines
(starting with a "#" character) can be present. These should be
followed by P lines of the form:
</P>
<PRE>I J
</PRE>
<P>where P is the number of processors LAMMPS was launched with. Note
that if running in multi-partition mode (see the -partition switch
above) P is the total number of processors in all partitions. The I
and J values describe a permutation of the P processors. Every I and
J should be values from 0 to P-1 inclusive. In the set of P I values,
every proc ID should appear exactly once. Ditto for the set of P J
values. A single I,J pairing means that the physical processor with
rank I in the original MPI communicator will have rank J in the
reordered communicator.
</P>
<P>Note that rank ordering can also be specified by many MPI
implementations, either by environment variables that specify how to
order physical processors, or by config files that specify what
physical processors to assign to each MPI rank. The -reorder switch
simply gives you a portable way to do this without relying on MPI
itself. See the <A HREF = "processors">processors out</A> command for how to output
info on the final assignment of physical processors to the LAMMPS
simulation domain.
</P>
<PRE>-screen file
</PRE>
<P>Specify a file for LAMMPS to write its screen information to. In
one-partition mode, if the switch is not used, LAMMPS writes to the
screen. If this switch is used, LAMMPS writes to the specified file
instead and you will see no screen output. In multi-partition mode,
if the switch is not used, hi-level status information is written to
the screen. Each partition also writes to a screen.N file where N is
the partition ID. If the switch is specified in multi-partition mode,
the hi-level screen dump is named "file" and each partition also
writes screen information to a file.N. For both one-partition and
multi-partition mode, if the specified file is "none", then no screen
output is performed. Option -pscreen will override the name of the
partition screen files file.N.
</P>
<PRE>-suffix style args
</PRE>
<P>Use variants of various styles if they exist. The specified style can
be <I>cuda</I>, <I>gpu</I>, <I>intel</I>, <I>kk</I>, <I>omp</I>, or <I>opt</I>. These refer to
optional packages that LAMMPS can be built with, as described above in
<A HREF = "#start_3">Section 2.3</A>. The "cuda" style corresponds to the USER-CUDA
package, the "gpu" style to the GPU package, the "intel" style to the
USER-INTEL package, the "kk" style to the KOKKOS package, the "opt"
style to the OPT package, and the "omp" style to the USER-OMP package.
</P>
<P>As an example, all of the packages provide a <A HREF = "pair_lj.html">pair_style
lj/cut</A> variant, with style names lj/cut/cuda,
lj/cut/gpu, lj/cut/intel, lj/cut/kk, lj/cut/omp, or lj/cut/opt. A
variant styles can be specified explicitly in your input script,
e.g. pair_style lj/cut/gpu. If the -suffix switch is used, you do not
need to modify your input script. The specified suffix
(cuda,gpu,intel,kk,omp,opt) is automatically appended whenever your
input script command creates a new <A HREF = "atom_style.html">atom</A>,
<A HREF = "pair_style.html">pair</A>, <A HREF = "fix.html">fix</A>, <A HREF = "compute.html">compute</A>, or
<A HREF = "run_style.html">run</A> style. If the variant version does not exist,
the standard version is created.
</P>
<P>For the GPU package, using this command-line switch also invokes the
default GPU settings, as if the command "package gpu force/neigh 0 0
1" were used at the top of your input script. These settings can be
changed by using the <A HREF = "package.html">package gpu</A> command in your script
if desired.
</P>
<P>For the USER-INTEL package, using this command-line switch also invokes the
default USER-INTEL settings, as if the command "package intel * mixed
balance -1" were used at the top of your input script. These settings
can be changed by using the <A HREF = "package.html">package intel</A> command in
your script if desired. If the USER-OMP package is installed, the
intel suffix will make the omp suffix a second choice, if a requested
style is not available in the USER-INTEL package.
</P>
<P>For the KOKKOS package, using this command-line switch also invokes
the default KOKKOS settings, as if the command "package kokkos neigh
full comm/exchange host comm/forward host " were used at the top of
your input script. These settings can be changed by using the
<A HREF = "package.html">package kokkos</A> command in your script if desired.
</P>
<P>For the OMP package, using this command-line switch also invokes the
default OMP settings, as if the command "package omp *" were used at
the top of your input script. These settings can be changed by using
the <A HREF = "package.html">package omp</A> command in your script if desired.
</P>
<P>The <A HREF = "suffix.html">suffix</A> command can also be used to set a suffix and
it can also turn off or back on any suffix setting made via the
command line.
</P>
<PRE>-var name value1 value2 ...
</PRE>
<P>Specify a variable that will be defined for substitution purposes when
the input script is read. "Name" is the variable name which can be a
single character (referenced as $x in the input script) or a full
string (referenced as ${abc}). An <A HREF = "variable.html">index-style
variable</A> will be created and populated with the
subsequent values, e.g. a set of filenames. Using this command-line
option is equivalent to putting the line "variable name index value1
value2 ..." at the beginning of the input script. Defining an index
variable as a command-line argument overrides any setting for the same
index variable in the input script, since index variables cannot be
re-defined. See the <A HREF = "variable.html">variable</A> command for more info on
defining index and other kinds of variables and <A HREF = "Section_commands.html#cmd_2">this
section</A> for more info on using variables
in input scripts.
</P>
<P>NOTE: Currently, the command-line parser looks for arguments that
start with "-" to indicate new switches. Thus you cannot specify
multiple variable values if any of they start with a "-", e.g. a
negative numeric value. It is OK if the first value1 starts with a
"-", since it is automatically skipped.
</P>
<HR>
<H4><A NAME = "start_8"></A>2.8 LAMMPS screen output
</H4>
<P>As LAMMPS reads an input script, it prints information to both the
screen and a log file about significant actions it takes to setup a
simulation. When the simulation is ready to begin, LAMMPS performs
various initializations and prints the amount of memory (in MBytes per
processor) that the simulation requires. It also prints details of
the initial thermodynamic state of the system. During the run itself,
thermodynamic information is printed periodically, every few
timesteps. When the run concludes, LAMMPS prints the final
thermodynamic state and a total run time for the simulation. It then
appends statistics about the CPU time and storage requirements for the
simulation. An example set of statistics is shown here:
</P>
<PRE>Loop time of 49.002 on 2 procs for 2004 atoms
</PRE>
<PRE>Pair time (%) = 35.0495 (71.5267)
Bond time (%) = 0.092046 (0.187841)
Kspce time (%) = 6.42073 (13.103)
Neigh time (%) = 2.73485 (5.5811)
Comm time (%) = 1.50291 (3.06703)
Outpt time (%) = 0.013799 (0.0281601)
Other time (%) = 2.13669 (4.36041)
</PRE>
<PRE>Nlocal: 1002 ave, 1015 max, 989 min
Histogram: 1 0 0 0 0 0 0 0 0 1
Nghost: 8720 ave, 8724 max, 8716 min
Histogram: 1 0 0 0 0 0 0 0 0 1
Neighs: 354141 ave, 361422 max, 346860 min
Histogram: 1 0 0 0 0 0 0 0 0 1
</PRE>
<PRE>Total # of neighbors = 708282
Ave neighs/atom = 353.434
Ave special neighs/atom = 2.34032
Number of reneighborings = 42
Dangerous reneighborings = 2
</PRE>
<P>The first section gives the breakdown of the CPU run time (in seconds)
into major categories. The second section lists the number of owned
atoms (Nlocal), ghost atoms (Nghost), and pair-wise neighbors stored
per processor. The max and min values give the spread of these values
across processors with a 10-bin histogram showing the distribution.
The total number of histogram counts is equal to the number of
processors.
</P>
<P>The last section gives aggregate statistics for pair-wise neighbors
and special neighbors that LAMMPS keeps track of (see the
<A HREF = "special_bonds.html">special_bonds</A> command). The number of times
neighbor lists were rebuilt during the run is given as well as the
number of potentially "dangerous" rebuilds. If atom movement
triggered neighbor list rebuilding (see the
<A HREF = "neigh_modify.html">neigh_modify</A> command), then dangerous
reneighborings are those that were triggered on the first timestep
atom movement was checked for. If this count is non-zero you may wish
to reduce the delay factor to insure no force interactions are missed
by atoms moving beyond the neighbor skin distance before a rebuild
takes place.
</P>
<P>If an energy minimization was performed via the
<A HREF = "minimize.html">minimize</A> command, additional information is printed,
e.g.
</P>
<PRE>Minimization stats:
E initial, next-to-last, final = -0.895962 -2.94193 -2.94342
Gradient 2-norm init/final= 1920.78 20.9992
Gradient inf-norm init/final= 304.283 9.61216
Iterations = 36
Force evaluations = 177
</PRE>
<P>The first line lists the initial and final energy, as well as the
energy on the next-to-last iteration. The next 2 lines give a measure
of the gradient of the energy (force on all atoms). The 2-norm is the
"length" of this force vector; the inf-norm is the largest component.
The last 2 lines are statistics on how many iterations and
force-evaluations the minimizer required. Multiple force evaluations
are typically done at each iteration to perform a 1d line minimization
in the search direction.
</P>
<P>If a <A HREF = "kspace_style.html">kspace_style</A> long-range Coulombics solve was
performed during the run (PPPM, Ewald), then additional information is
printed, e.g.
</P>
<PRE>FFT time (% of Kspce) = 0.200313 (8.34477)
FFT Gflps 3d 1d-only = 2.31074 9.19989
</PRE>
<P>The first line gives the time spent doing 3d FFTs (4 per timestep) and
the fraction it represents of the total KSpace time (listed above).
Each 3d FFT requires computation (3 sets of 1d FFTs) and communication
(transposes). The total flops performed is 5Nlog_2(N), where N is the
number of points in the 3d grid. The FFTs are timed with and without
the communication and a Gflop rate is computed. The 3d rate is with
communication; the 1d rate is without (just the 1d FFTs). Thus you
can estimate what fraction of your FFT time was spent in
communication, roughly 75% in the example above.
</P>
<HR>
<H4><A NAME = "start_9"></A>2.9 Tips for users of previous LAMMPS versions
</H4>
<P>The current C++ began with a complete rewrite of LAMMPS 2001, which
was written in F90. Features of earlier versions of LAMMPS are listed
in <A HREF = "Section_history.html">Section_history</A>. The F90 and F77 versions
(2001 and 99) are also freely distributed as open-source codes; check
the <A HREF = "http://lammps.sandia.gov">LAMMPS WWW Site</A> for distribution information if you prefer
those versions. The 99 and 2001 versions are no longer under active
development; they do not have all the features of C++ LAMMPS.
</P>
<P>If you are a previous user of LAMMPS 2001, these are the most
significant changes you will notice in C++ LAMMPS:
</P>
<P>(1) The names and arguments of many input script commands have
changed. All commands are now a single word (e.g. read_data instead
of read data).
</P>
<P>(2) All the functionality of LAMMPS 2001 is included in C++ LAMMPS,
but you may need to specify the relevant commands in different ways.
</P>
<P>(3) The format of the data file can be streamlined for some problems.
See the <A HREF = "read_data.html">read_data</A> command for details. The data file
section "Nonbond Coeff" has been renamed to "Pair Coeff" in C++ LAMMPS.
</P>
<P>(4) Binary restart files written by LAMMPS 2001 cannot be read by C++
LAMMPS with a <A HREF = "read_restart.html">read_restart</A> command. This is
because they were output by F90 which writes in a different binary
format than C or C++ writes or reads. Use the <I>restart2data</I> tool
provided with LAMMPS 2001 to convert the 2001 restart file to a text
data file. Then edit the data file as necessary before using the C++
LAMMPS <A HREF = "read_data.html">read_data</A> command to read it in.
</P>
<P>(5) There are numerous small numerical changes in C++ LAMMPS that mean
you will not get identical answers when comparing to a 2001 run.
However, your initial thermodynamic energy and MD trajectory should be
close if you have setup the problem for both codes the same.
</P>
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