2011-06-01 07:08:32 +08:00
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<CENTER><A HREF = "http://lammps.sandia.gov">LAMMPS WWW Site</A> - <A HREF = "Manual.html">LAMMPS Documentation</A> - <A HREF = "Section_commands.html#comm">LAMMPS Commands</A>
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<HR>
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<H3>package command
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</H3>
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<P><B>Syntax:</B>
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</P>
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<PRE>package style args
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</PRE>
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2011-08-17 22:20:30 +08:00
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<UL><LI>style = <I>gpu</I> or <I>cuda</I> or <I>omp</I>
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2011-06-01 07:08:32 +08:00
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2011-08-17 22:20:30 +08:00
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<LI>args = arguments specific to the style
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2011-06-01 07:08:32 +08:00
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2011-08-17 22:22:48 +08:00
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<PRE> <I>gpu</I> args = mode first last split
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mode = force or force/neigh
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first = ID of first GPU to be used on each node
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last = ID of last GPU to be used on each node
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split = fraction of particles assigned to the GPU
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<I>cuda</I> args = to be determined
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<I>omp</I> args = Nthreads
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Nthreads = # of OpenMP threads to associate with each MPI process
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2011-06-01 07:08:32 +08:00
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</PRE>
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</UL>
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<P><B>Examples:</B>
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</P>
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2011-08-17 22:20:30 +08:00
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<PRE>package gpu force 0 0 1.0
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package gpu force 0 0 0.75
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package gpu force/neigh 0 0 1.0
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package gpu force/neigh 0 1 -1.0
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package cuda blah
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package omp 4
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2011-06-01 07:08:32 +08:00
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</PRE>
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<P><B>Description:</B>
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</P>
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2011-08-17 22:20:30 +08:00
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<P>This command invokes package-specific settings. Currently the
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following packages use it: GPU, USER-CUDA, and USER-OMP.
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</P>
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2011-08-17 22:22:48 +08:00
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<P>See <A HREF = "Section_accelerate.html">this section</A> of the manual for more
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2011-08-17 22:20:30 +08:00
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details about using these various packages for accelerating
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a LAMMPS calculation.
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</P>
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<HR>
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<P>The <I>gpu</I> style invokes options associated with the use of the GPU
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package. It allows you to select and initialize GPUs to be used for
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acceleration via this package and configure how the GPU acceleration
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is performed. These settings are required in order to use any style
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with GPU acceleration.
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</P>
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<P>The <I>mode</I> setting specifies where neighbor list calculations will be
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performed. If <I>mode</I> is force, neighbor list calculation is performed
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on the CPU. If <I>mode</I> is force/neigh, neighbor list calculation is
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performed on the GPU. GPU neighbor list calculation currently cannot
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be used with a triclinic box. GPU neighbor list calculation currently
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cannot be used with <A HREF = "pair_hybrid.html">hybrid</A> pair styles. GPU
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neighbor lists are not compatible with styles that are not
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GPU-enabled. When a non-GPU enabled style requires a neighbor list,
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it will also be built using CPU routines. In these cases, it will
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typically be more efficient to only use CPU neighbor list builds.
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</P>
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<P>The <I>first</I> and <I>last</I> settings specify the GPUs that will be used for
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simulation. On each node, the GPU IDs in the inclusive range from
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<I>first</I> to <I>last</I> will be used.
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</P>
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<P>The <I>split</I> setting can be used for load balancing force calculation
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work between CPU and GPU cores in GPU-enabled pair styles. If 0 <
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<I>split</I> < 1.0, a fixed fraction of particles is offloaded to the GPU
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while force calculation for the other particles occurs simulataneously
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on the CPU. If <I>split</I><0, the optimal fraction (based on CPU and GPU
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timings) is calculated every 25 timesteps. If <I>split</I> = 1.0, all force
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calculations for GPU accelerated pair styles are performed on the
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GPU. In this case, <A HREF = "pair_hybrid.html">hybrid</A>, <A HREF = "bond_style.html">bond</A>,
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<A HREF = "angle_style.html">angle</A>, <A HREF = "dihedral_style.html">dihedral</A>,
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<A HREF = "improper_style.html">improper</A>, and <A HREF = "kspace_style.html">long-range</A>
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calculations can be performed on the CPU while the GPU is performing
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force calculations for the GPU-enabled pair style. If all CPU force
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computations complete before the GPU, LAMMPS will block until the GPU
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has finished before continuing the timestep.
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</P>
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<P>As an example, if you have two GPUs per node and 8 CPU cores per node,
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and would like to run on 4 nodes (32 cores) with dynamic balancing of
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force calculation across CPU and GPU cores, you could specify
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2011-06-01 07:08:32 +08:00
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</P>
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2011-08-17 22:20:30 +08:00
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<PRE>package gpu force/neigh 0 1 -1
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</PRE>
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<P>In this case, all CPU cores and GPU devices on the nodes would be
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utilized. Each GPU device would be shared by 4 CPU cores. The CPU
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cores would perform force calculations for some fraction of the
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particles at the same time the GPUs performed force calculation for
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the other particles.
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</P>
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<HR>
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2011-06-01 07:08:32 +08:00
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<P>The <I>cuda</I> style invokes options associated with the use of the
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2011-08-18 05:55:22 +08:00
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USER-CUDA package. These still need to be documented.
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2011-08-17 22:20:30 +08:00
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</P>
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<HR>
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<P>The <I>omp</I> style invokes options associated with the use of the
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USER-OMP package.
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2011-06-01 07:08:32 +08:00
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</P>
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2011-08-17 22:20:30 +08:00
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<P>The only setting to make is the number of OpenMP threads to be
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allocated for each MPI process. For example, if your system has nodes
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with dual quad-core processors, it has a total of 8 cores per node.
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You could run MPI on 2 cores on each node (e.g. using options for the
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mpirun command), and set the <I>Nthreads</I> setting to 4. This would
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effectively use all 8 cores on each node. Since each MPI process
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would spawn 4 threads (one of which runs as part of the MPI process
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itself).
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</P>
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<P>For performance reasons, you should not set <I>Nthreads</I> to more threads
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than there are physical cores, but LAMMPS does not check for this.
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</P>
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<HR>
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2011-06-01 07:08:32 +08:00
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<P><B>Restrictions:</B>
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</P>
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2011-08-17 22:20:30 +08:00
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<P>This command cannot be used after the simulation box is defined by a
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<A HREF = "read_data.html">read_data</A> or <A HREF = "create_box.html">create_box</A> command.
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</P>
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2011-06-01 07:08:32 +08:00
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<P>The cuda style of this command can only be invoked if LAMMPS was built
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with the USER-CUDA package. See the <A HREF = "Section_start.html#2_3">Making
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LAMMPS</A> section for more info.
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</P>
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2011-08-17 22:20:30 +08:00
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<P>The gpu style of this command can only be invoked if LAMMPS was built
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with the GPU package. See the <A HREF = "Section_start.html#2_3">Making LAMMPS</A>
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section for more info.
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2011-06-01 07:08:32 +08:00
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</P>
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2011-08-17 22:20:30 +08:00
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<P>The omp style of this command can only be invoked if LAMMPS was built
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with the USER-OMP package. See the <A HREF = "Section_start.html#2_3">Making
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LAMMPS</A> section for more info.
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2011-06-01 07:08:32 +08:00
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</P>
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2011-08-17 22:20:30 +08:00
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<P><B>Related commands:</B> none
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2011-06-01 07:08:32 +08:00
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</P>
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<P><B>Default:</B> none
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</P>
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</HTML>
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