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lammps.py
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Tue, May 14, 15:33

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:
def __init__(self,name="",cmdargs=None,ptr=None):
# determine module location
modpath = dirname(abspath(getsourcefile(lambda:0)))
# load liblammps.so by default
# if name = "g++", load liblammps_g++.so
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:
type,value,tb = sys.exc_info()
traceback.print_exception(type,value,tb)
raise OSError,"Could not load LAMMPS dynamic library from %s" % modpath
# if no ptr provided, create an instance of LAMMPS
# don't know how to pass an MPI communicator from PyPar
# 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:
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):
self.lib.lammps_file(self.lmp,file)
def command(self,cmd):
self.lib.lammps_command(self.lmp,cmd)
def extract_global(self,name,type):
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):
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):
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):
if type == 0:
if style > 0: return None
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
if type == 1:
self.lib.lammps_extract_fix.restype = POINTER(c_double)
ptr = self.lib.lammps_extract_fix(self.lmp,id,style,type,i,j)
return ptr
if type == 2:
self.lib.lammps_extract_fix.restype = POINTER(POINTER(c_double))
ptr = self.lib.lammps_extract_fix(self.lmp,id,style,type,i,j)
return ptr
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):
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):
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):
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):
self.lib.lammps_scatter_atoms(self.lmp,name,type,count,data)

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