Have PyTorch interface for MLIAP working in Kokkos. This uses cuPy and a simple example is provided

examples/mliap/mliap_pytorch_Ta06A_kokkos.py

@@ -0,0 +1,104 @@
+# Demonstrate how to load a model from the python side.
+# This is essentially the same as in.mliap.pytorch.Ta06A
+# except that python is the driving program, and lammps
+# is in library mode.
+
+before_loading =\
+"""# Demonstrate MLIAP/PyTorch interface to linear SNAP potential
+
+# Initialize simulation
+
+variable nsteps index 100
+variable nrep equal 4
+variable a equal 3.316
+units           metal
+
+# generate the box and atom positions using a BCC lattice
+
+variable nx equal ${nrep}
+variable ny equal ${nrep}
+variable nz equal ${nrep}
+
+boundary        p p p
+
+lattice         bcc $a
+region          box block 0 ${nx} 0 ${ny} 0 ${nz}
+create_box      1 box
+create_atoms    1 box
+
+mass 1 180.88
+
+# choose potential
+
+# DATE: 2014-09-05 UNITS: metal CONTRIBUTOR: Aidan Thompson athomps@sandia.gov CITATION: Thompson, Swiler, Trott, Foiles and Tucker, arxiv.org, 1409.3880 (2014)
+
+# Definition of SNAP potential Ta_Cand06A
+# Assumes 1 LAMMPS atom type
+
+variable zblcutinner equal 4
+variable zblcutouter equal 4.8
+variable zblz equal 73
+
+# Specify hybrid with SNAP, ZBL
+
+pair_style hybrid/overlay &
+zbl ${zblcutinner} ${zblcutouter} &
+mliap model mliappy LATER &
+descriptor sna Ta06A.mliap.descriptor
+pair_coeff 1 1 zbl ${zblz} ${zblz}
+pair_coeff * * mliap Ta
+"""
+after_loading =\
+"""
+
+# Setup output
+
+compute  eatom all pe/atom
+compute  energy all reduce sum c_eatom
+
+compute  satom all stress/atom NULL
+compute  str all reduce sum c_satom[1] c_satom[2] c_satom[3]
+variable press equal (c_str[1]+c_str[2]+c_str[3])/(3*vol)
+
+thermo_style    custom step temp epair c_energy etotal press v_press
+thermo          10
+thermo_modify norm yes
+
+# Set up NVE run
+
+timestep 0.5e-3
+neighbor 1.0 bin
+neigh_modify once no every 1 delay 0 check yes
+
+# Run MD
+
+velocity all create 300.0 4928459 loop geom
+fix 1 all nve
+run             ${nsteps}
+"""
+
+import lammps
+
+lmp = lammps.lammps(cmdargs=['-k', 'on', 'g', '1', '-sf', 'kk', '-pk', 'kokkos', 'neigh', 'full', 'newton', 'on', '-echo', 'both'])
+
+# Before defining the pair style, one must do the following:
+import lammps.mliap
+lammps.mliap.activate_mliappy_kokkos(lmp)
+# Otherwise, when running lammps in library mode,
+# you will get an error:
+# "ERROR: Loading MLIAPPY coupling module failure."
+
+# Setup the simulation and declare an empty model
+# by specifying model filename as "LATER"
+lmp.commands_string(before_loading)
+
+# Define the model however you like. In this example
+# we load it from disk:
+import torch
+model = torch.load('Ta06A.mliap.pytorch.model.pt')
+
+# Connect the PyTorch model to the mliap pair style.
+lammps.mliap.load_model_kokkos(model)
+  
+# run the simulation with the mliap pair style
+lmp.commands_string(after_loading)