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! LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
! www.cs.sandia.gov/~sjplimp/lammps.html
! Steve Plimpton, sjplimp@sandia.gov, Sandia National Laboratories
!
! 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.
! f_driver = simple example of how an umbrella program
! can invoke LAMMPS as a library on some subset of procs
! Syntax: simpleF P in.lammps
! P = # of procs to run LAMMPS on
! must be <= # of procs the driver code itself runs on
! in.lammps = LAMMPS input script
! See README for compilation instructions
PROGRAM f_driver
IMPLICIT NONE
INCLUDE 'mpif.h'
INTEGER, PARAMETER :: fp=20
INTEGER :: n, narg, ierr, me, nprocs, natoms
INTEGER :: lammps, nprocs_lammps, comm_lammps
INTEGER (kind=8) :: ptr
REAL (kind=8), ALLOCATABLE :: x(:)
REAL (kind=8), PARAMETER :: epsilon=0.1
CHARACTER (len=64) :: arg
CHARACTER (len=1024) :: line
! setup MPI and various communicators
! driver runs on all procs in MPI_COMM_WORLD
! comm_lammps only has 1st P procs (could be all or any subset)
CALL mpi_init(ierr)
narg = command_argument_count()
IF (narg /= 2) THEN
PRINT *, 'Syntax: simpleF P in.lammps'
CALL mpi_abort(MPI_COMM_WORLD,1,ierr)
END IF
CALL mpi_comm_rank(MPI_COMM_WORLD,me,ierr);
CALL mpi_comm_size(MPI_COMM_WORLD,nprocs,ierr);
CALL get_command_argument(1,arg)
READ (arg,'(I10)') nprocs_lammps
IF (nprocs_lammps > nprocs) THEN
IF (me == 0) THEN
PRINT *, 'ERROR: LAMMPS cannot use more procs than available'
CALL mpi_abort(MPI_COMM_WORLD,2,ierr)
END IF
END IF
lammps = 0
IF (me < nprocs_lammps) THEN
lammps = 1
ELSE
lammps = MPI_UNDEFINED
END IF
CALL mpi_comm_split(MPI_COMM_WORLD,lammps,0,comm_lammps,ierr)
! open LAMMPS input script on rank zero
CALL get_command_argument(2,arg)
OPEN(UNIT=fp, FILE=arg, ACTION='READ', STATUS='OLD', IOSTAT=ierr)
IF (ierr /= 0) THEN
PRINT *, 'ERROR: Could not open LAMMPS input script'
CALL mpi_abort(MPI_COMM_WORLD,3,ierr);
END IF
! run the input script thru LAMMPS one line at a time until end-of-file
! driver proc 0 reads a line, Bcasts it to all procs
! (could just send it to proc 0 of comm_lammps and let it Bcast)
! all LAMMPS procs call lammps_command() on the line */
IF (lammps == 1) CALL lammps_open(comm_lammps,ptr)
n = 0
DO
IF (me == 0) THEN
READ (UNIT=fp, FMT='(A)', IOSTAT=ierr) line
n = 0
IF (ierr == 0) THEN
n = LEN(TRIM(line))
IF (n == 0 ) THEN
line = ' '
n = 1
END IF
END IF
END IF
CALL mpi_bcast(n,1,MPI_INTEGER,0,MPI_COMM_WORLD,ierr)
IF (n == 0) EXIT
CALL mpi_bcast(line,n,MPI_CHARACTER,0,MPI_COMM_WORLD,ierr)
IF (lammps == 1) CALL lammps_command(ptr,line,n)
END DO
CLOSE(UNIT=fp)
! run 10 more steps
! get coords from LAMMPS
! change coords of 1st atom
! put coords back into LAMMPS
! run a single step with changed coords */
IF (lammps == 1) THEN
CALL lammps_command(ptr,'run 10',6)
CALL lammps_get_natoms(ptr,natoms)
ALLOCATE(x(3*natoms))
CALL lammps_gather_atoms(ptr,'x',1,3,x);
x(1) = x(1) + epsilon
CALL lammps_scatter_atoms(ptr,'x',1,3,x);
DEALLOCATE(x)
CALL lammps_command(ptr,'run 1',5);
END IF
! free LAMMPS object
IF (lammps == 1) CALL lammps_close(ptr);
! close down MPI
CALL mpi_finalize(ierr)
END PROGRAM f_driver
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