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lammps.py
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lammps.py
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# ----------------------------------------------------------------------
# LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
# http://lammps.sandia.gov, Sandia National Laboratories
# Steve Plimpton, sjplimp@sandia.gov
#
# Copyright (2003) Sandia Corporation. Under the terms of Contract
# DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
# certain rights in this software. This software is distributed under
# the GNU General Public License.
#
# See the README file in the top-level LAMMPS directory.
# -------------------------------------------------------------------------
# Python wrapper on LAMMPS library via ctypes
import sys,traceback,types
from ctypes import *
from os.path import dirname,abspath,join
from inspect import getsourcefile
class lammps:
# detect if Python is using version of mpi4py that can pass a communicator
has_mpi4py_v2 = False
try:
from mpi4py import MPI
from mpi4py import __version__ as mpi4py_version
if mpi4py_version.split('.')[0] == '2':
has_mpi4py_v2 = True
except:
pass
# create instance of LAMMPS
def __init__(self,name="",cmdargs=None,ptr=None,comm=None):
# determine module location
modpath = dirname(abspath(getsourcefile(lambda:0)))
# load liblammps.so unless name is given.
# e.g. if name = "g++", load liblammps_g++.so
# try loading the LAMMPS shared object from the location
# of lammps.py with an absolute path (so that LD_LIBRARY_PATH
# does not need to be set for regular installations.
# fall back to loading with a relative path, which typically
# requires LD_LIBRARY_PATH to be set appropriately.
try:
if not name: self.lib = CDLL(join(modpath,"liblammps.so"),RTLD_GLOBAL)
else: self.lib = CDLL(join(modpath,"liblammps_%s.so" % name),RTLD_GLOBAL)
except:
if not name: self.lib = CDLL("liblammps.so",RTLD_GLOBAL)
else: self.lib = CDLL("liblammps_%s.so" % name,RTLD_GLOBAL)
# if no ptr provided, create an instance of LAMMPS
# don't know how to pass an MPI communicator from PyPar
# but we can pass an MPI communicator from mpi4py v2.0.0 and later
# no_mpi call lets LAMMPS use MPI_COMM_WORLD
# cargs = array of C strings from args
# if ptr, then are embedding Python in LAMMPS input script
# ptr is the desired instance of LAMMPS
# just convert it to ctypes ptr and store in self.lmp
if not ptr:
# with mpi4py v2, can pass MPI communicator to LAMMPS
# need to adjust for type of MPI communicator object
# allow for int (like MPICH) or void* (like OpenMPI)
if lammps.has_mpi4py_v2 and comm != None:
if lammps.MPI._sizeof(lammps.MPI.Comm) == sizeof(c_int):
MPI_Comm = c_int
else:
MPI_Comm = c_void_p
narg = 0
cargs = 0
if cmdargs:
cmdargs.insert(0,"lammps.py")
narg = len(cmdargs)
cargs = (c_char_p*narg)(*cmdargs)
self.lib.lammps_open.argtypes = [c_int, c_char_p*narg, \
MPI_Comm, c_void_p()]
else:
self.lib.lammps_open.argtypes = [c_int, c_int, \
MPI_Comm, c_void_p()]
self.lib.lammps_open.restype = None
self.opened = 1
self.lmp = c_void_p()
comm_ptr = lammps.MPI._addressof(comm)
comm_val = MPI_Comm.from_address(comm_ptr)
self.lib.lammps_open(narg,cargs,comm_val,byref(self.lmp))
else:
self.opened = 1
if cmdargs:
cmdargs.insert(0,"lammps.py")
narg = len(cmdargs)
cargs = (c_char_p*narg)(*cmdargs)
self.lmp = c_void_p()
self.lib.lammps_open_no_mpi(narg,cargs,byref(self.lmp))
else:
self.lmp = c_void_p()
self.lib.lammps_open_no_mpi(0,None,byref(self.lmp))
# could use just this if LAMMPS lib interface supported it
# self.lmp = self.lib.lammps_open_no_mpi(0,None)
else:
self.opened = 0
# magic to convert ptr to ctypes ptr
pythonapi.PyCObject_AsVoidPtr.restype = c_void_p
pythonapi.PyCObject_AsVoidPtr.argtypes = [py_object]
self.lmp = c_void_p(pythonapi.PyCObject_AsVoidPtr(ptr))
def __del__(self):
if self.lmp and self.opened: self.lib.lammps_close(self.lmp)
def close(self):
if self.opened: self.lib.lammps_close(self.lmp)
self.lmp = None
def version(self):
return self.lib.lammps_version(self.lmp)
def file(self,file):
file = file.encode()
self.lib.lammps_file(self.lmp,file)
def command(self,cmd):
cmd = cmd.encode()
self.lib.lammps_command(self.lmp,cmd)
def extract_global(self,name,type):
name = name.encode()
if type == 0:
self.lib.lammps_extract_global.restype = POINTER(c_int)
elif type == 1:
self.lib.lammps_extract_global.restype = POINTER(c_double)
else: return None
ptr = self.lib.lammps_extract_global(self.lmp,name)
return ptr[0]
def extract_atom(self,name,type):
name = name.encode()
if type == 0:
self.lib.lammps_extract_atom.restype = POINTER(c_int)
elif type == 1:
self.lib.lammps_extract_atom.restype = POINTER(POINTER(c_int))
elif type == 2:
self.lib.lammps_extract_atom.restype = POINTER(c_double)
elif type == 3:
self.lib.lammps_extract_atom.restype = POINTER(POINTER(c_double))
else: return None
ptr = self.lib.lammps_extract_atom(self.lmp,name)
return ptr
def extract_compute(self,id,style,type):
id = id.encode()
if type == 0:
if style > 0: return None
self.lib.lammps_extract_compute.restype = POINTER(c_double)
ptr = self.lib.lammps_extract_compute(self.lmp,id,style,type)
return ptr[0]
if type == 1:
self.lib.lammps_extract_compute.restype = POINTER(c_double)
ptr = self.lib.lammps_extract_compute(self.lmp,id,style,type)
return ptr
if type == 2:
self.lib.lammps_extract_compute.restype = POINTER(POINTER(c_double))
ptr = self.lib.lammps_extract_compute(self.lmp,id,style,type)
return ptr
return None
# in case of global datum, free memory for 1 double via lammps_free()
# double was allocated by library interface function
def extract_fix(self,id,style,type,i=0,j=0):
id = ide.encode()
if style == 0:
self.lib.lammps_extract_fix.restype = POINTER(c_double)
ptr = self.lib.lammps_extract_fix(self.lmp,id,style,type,i,j)
result = ptr[0]
self.lib.lammps_free(ptr)
return result
elif (style == 1) or (style == 2):
if type == 1:
self.lib.lammps_extract_fix.restype = POINTER(c_double)
elif type == 2:
self.lib.lammps_extract_fix.restype = POINTER(POINTER(c_double))
else:
return None
ptr = self.lib.lammps_extract_fix(self.lmp,id,style,type,i,j)
return ptr
else:
return None
# free memory for 1 double or 1 vector of doubles via lammps_free()
# for vector, must copy nlocal returned values to local c_double vector
# memory was allocated by library interface function
def extract_variable(self,name,group,type):
name = name.encode()
group = group.encode()
if type == 0:
self.lib.lammps_extract_variable.restype = POINTER(c_double)
ptr = self.lib.lammps_extract_variable(self.lmp,name,group)
result = ptr[0]
self.lib.lammps_free(ptr)
return result
if type == 1:
self.lib.lammps_extract_global.restype = POINTER(c_int)
nlocalptr = self.lib.lammps_extract_global(self.lmp,"nlocal")
nlocal = nlocalptr[0]
result = (c_double*nlocal)()
self.lib.lammps_extract_variable.restype = POINTER(c_double)
ptr = self.lib.lammps_extract_variable(self.lmp,name,group)
for i in xrange(nlocal): result[i] = ptr[i]
self.lib.lammps_free(ptr)
return result
return None
# set variable value
# value is converted to string
# returns 0 for success, -1 if failed
def set_variable(self,name,value):
name = name.encode()
value = str(value).encode()
return self.lib.lammps_set_variable(self.lmp,name,str(value))
# return total number of atoms in system
def get_natoms(self):
return self.lib.lammps_get_natoms(self.lmp)
# return vector of atom properties gathered across procs, ordered by atom ID
def gather_atoms(self,name,type,count):
name = name.encode()
natoms = self.lib.lammps_get_natoms(self.lmp)
if type == 0:
data = ((count*natoms)*c_int)()
self.lib.lammps_gather_atoms(self.lmp,name,type,count,data)
elif type == 1:
data = ((count*natoms)*c_double)()
self.lib.lammps_gather_atoms(self.lmp,name,type,count,data)
else: return None
return data
# scatter vector of atom properties across procs, ordered by atom ID
# assume vector is of correct type and length, as created by gather_atoms()
def scatter_atoms(self,name,type,count,data):
name = name.encode()
self.lib.lammps_scatter_atoms(self.lmp,name,type,count,data)

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