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sjplimp
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@ -1,15 +1,21 @@
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This directory has a simple C and C++ code that shows how LAMMPS can
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be linked to a driver application as a library. The purpose is to
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illustrate how another code could perform computations while using
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LAMMPS to perform MD, or how an umbrella code or script could call
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both LAMMPS and some other code to perform a coupled calculation.
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This directory has a simple C, C++, and Fortran code that shows how
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LAMMPS can be linked to a driver application as a library. The purpose
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is to illustrate how another code could perform computations while
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using LAMMPS to perform MD on all or a subset of the processors, or
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how an umbrella code or script could call both LAMMPS and some other
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code to perform a coupled calculation.
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simple.cpp is the C++ driver
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simple.c is the C driver
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simple.cpp is the C++ driver
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simple.c is the C driver
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simple.f90 is the Fortran driver
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libfwrapper.c is the Fortran-to-C wrapper
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The 2 codes do the same thing, so you can compare them to see how to
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drive LAMMPS in this manner. The C driver is similar in spirit to
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what one could use from a Fortran program or scripting language.
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The 3 codes do the same thing, so you can compare them to see how to
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drive LAMMPS in this manner. The C driver is similar in spirit to what
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one could use to write a scripting language interface. The Fortran
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driver in addition requires a wrapper library that interfaces the C
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interface of the LAMMPS library to Fortran and also translates the MPI
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communicator from Fortran to C.
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You can then build either driver code with a compile line something
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like this, which includes paths to the LAMMPS library interface, MPI,
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@ -28,8 +34,17 @@ gcc -I/home/sjplimp/lammps/src -c simple.c
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gcc -L/home/sjplimp/lammps/src simple.o \
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-llmp_g++ -lfftw -lmpich -lpthread -lstdc++ -o simpleC
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You then run simpleCC or simpleC on a parallel machine on some number
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of processors Q with 2 arguments:
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This builds the Fortran wrapper and driver with the LAMMPS library
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using a Fortran and C compiler:
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cp ../fortran/libfwrapper.c .
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gcc -I/home/sjplimp/lammps/src -c libfwrapper.c
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gfortran -I/home/sjplimp/lammps/src -c simple.f90
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gfortran -L/home/sjplimp/lammps/src simple.o libfwrapper.o \
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-llmp_g++ -lfftw -lfmpich -lmpich -lpthread -lstdc++ -o simpleF
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You then run simpleCC, simpleC, or simpleF on a parallel machine
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on some number of processors Q with 2 arguments:
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mpirun -np Q simpleCC P in.lj
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@ -49,6 +64,11 @@ The C driver is calling C-style routines in the src/library.cpp file
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of LAMMPS. You could add any functions you wish to this file to
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manipulate LAMMPS data however you wish.
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The Fortran driver is using the same C-style routines, but requires an
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additional wrapper to make them Fortran callable. Only a subset of the
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library functions are currently wrapped, but it should be clear how to
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extend the wrapper if desired.
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The C++ driver does the same thing, except that it instantiates LAMMPS
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as an object first. Some of the functions in src/library.cpp can be
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invoked directly as methods within appropriate LAMMPS classes, which
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@ -0,0 +1,135 @@
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! LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
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! www.cs.sandia.gov/~sjplimp/lammps.html
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! Steve Plimpton, sjplimp@sandia.gov, Sandia National Laboratories
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!
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! Copyright (2003) Sandia Corporation. Under the terms of Contract
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! DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
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! certain rights in this software. This software is distributed under
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! the GNU General Public License.
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!
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! See the README file in the top-level LAMMPS directory.
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! f_driver = simple example of how an umbrella program
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! can invoke LAMMPS as a library on some subset of procs
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! Syntax: f_driver P in.lammps
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! P = # of procs to run LAMMPS on
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! must be <= # of procs the driver code itself runs on
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! in.lammps = LAMMPS input script
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! See README for compilation instructions
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PROGRAM f_driver
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IMPLICIT NONE
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INCLUDE 'mpif.h'
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INTEGER, PARAMETER :: fp=20
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INTEGER :: n, narg, ierr, me, nprocs, natoms
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INTEGER :: lammps, nprocs_lammps, comm_lammps
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INTEGER (kind=8) :: ptr
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REAL (kind=8), ALLOCATABLE :: x(:)
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REAL (kind=8), PARAMETER :: epsilon=0.1
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CHARACTER (len=64) :: arg
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CHARACTER (len=1024) :: line
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! setup MPI and various communicators
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! driver runs on all procs in MPI_COMM_WORLD
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! comm_lammps only has 1st P procs (could be all or any subset)
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CALL mpi_init(ierr)
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narg = command_argument_count()
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IF (narg /= 2) THEN
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PRINT *, 'Syntax: f_driver P in.lammps'
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CALL mpi_abort(MPI_COMM_WORLD,1,ierr)
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END IF
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CALL mpi_comm_rank(MPI_COMM_WORLD,me,ierr);
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CALL mpi_comm_size(MPI_COMM_WORLD,nprocs,ierr);
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CALL get_command_argument(1,arg)
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READ (arg,'(I10)') nprocs_lammps
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IF (nprocs_lammps > nprocs) THEN
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IF (me == 0) THEN
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PRINT *, 'ERROR: LAMMPS cannot use more procs than available'
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CALL mpi_abort(MPI_COMM_WORLD,2,ierr)
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END IF
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END IF
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lammps = 0
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IF (me < nprocs_lammps) THEN
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lammps = 1
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ELSE
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lammps = MPI_UNDEFINED
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END IF
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CALL mpi_comm_split(MPI_COMM_WORLD,lammps,0,comm_lammps,ierr)
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! open LAMMPS input script on rank zero
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CALL get_command_argument(2,arg)
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OPEN(UNIT=fp, FILE=arg, ACTION='READ', STATUS='OLD', IOSTAT=ierr)
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IF (ierr /= 0) THEN
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PRINT *, 'ERROR: Could not open LAMMPS input script'
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CALL mpi_abort(MPI_COMM_WORLD,3,ierr);
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END IF
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! run the input script thru LAMMPS one line at a time until end-of-file
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! driver proc 0 reads a line, Bcasts it to all procs
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! (could just send it to proc 0 of comm_lammps and let it Bcast)
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! all LAMMPS procs call lammps_command() on the line */
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IF (lammps == 1) CALL lammps_open(comm_lammps,ptr)
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n = 0
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DO
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IF (me == 0) THEN
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READ (UNIT=fp, FMT='(A)', IOSTAT=ierr) line
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n = 0
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IF (ierr == 0) THEN
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n = LEN(TRIM(line))
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IF (n == 0 ) THEN
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line = ' '
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n = 1
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END IF
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END IF
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END IF
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CALL mpi_bcast(n,1,MPI_INTEGER,0,MPI_COMM_WORLD,ierr)
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IF (n == 0) EXIT
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CALL mpi_bcast(line,n,MPI_CHARACTER,0,MPI_COMM_WORLD,ierr)
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IF (lammps == 1) CALL lammps_command(ptr,line,n)
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END DO
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CLOSE(UNIT=fp)
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! run 10 more steps
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! get coords from LAMMPS
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! change coords of 1st atom
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! put coords back into LAMMPS
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! run a single step with changed coords */
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IF (lammps == 1) THEN
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CALL lammps_command(ptr,'run 10',6)
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CALL lammps_get_natoms(ptr,natoms)
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ALLOCATE(x(3*natoms))
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CALL lammps_get_coords(ptr,x)
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x(1) = x(1) + epsilon
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CALL lammps_put_coords(ptr,x)
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DEALLOCATE(x)
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CALL lammps_command(ptr,'run 1',5);
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END IF
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! free LAMMPS object
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IF (lammps == 1) CALL lammps_close(ptr);
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! close down MPI
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CALL mpi_finalize(ierr)
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END PROGRAM f_driver
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