Hi All,
I am trying to address the mpich2-1.2.1p1 issue regarding pmemd (and also
parts of sander I believe). This version of mpich2 does not accept aliasing
of send and receive buffers unless using the MPI2 MPI_IN_PLACE argument. The
fix I propose is:
use parallel_dat_mod
implicit none
! Formal arguments:
integer :: atm_cnt
double precision :: vec(3, atm_cnt)
! Local variables:
if ( MPI_VERSION == 2 ) then
if ( master ) then
call mpi_gatherv(MPI_IN_PLACE, &
vec_rcvcnts(mytaskid), mpi_double_precision, &
vec, vec_rcvcnts, vec_offsets, &
mpi_double_precision, 0, mpi_comm_world,
err_code_mpi)
else
!Pre MPI_VERSION 2 officially one cannot have send and receive buffers that
!alias each other, however, this has been working fine for gatherv for
!many years. It is only recent error checking in mpich2-1.2.1p1 which has
!caused problems.
call mpi_gatherv(vec(1, atm_offsets(mytaskid) + 1), &
vec_rcvcnts(mytaskid), mpi_double_precision, &
vec, vec_rcvcnts, vec_offsets, &
mpi_double_precision, 0, mpi_comm_world,
err_code_mpi)
end if
else
call mpi_gatherv(vec(1, atm_offsets(mytaskid) + 1), &
vec_rcvcnts(mytaskid), mpi_double_precision, &
vec, vec_rcvcnts, vec_offsets, &
mpi_double_precision, 0, mpi_comm_world, err_code_mpi)
end if
return
However, there are a few problems with this.
1) I do not know if MPI_VERSION is always defined in every MPI
implementation. I guess it is, but not sure.
2) MPI_IN_PLACE is only defined if this is a MPI2 implementation.
Any ideas how best to address this.
I thought about:
#ifndef MPI_VERSION
# define MPI_VERSION 1
#endif
#ifndef MPI_IN_PLACE
# define MPI_IN_PLACE 0
#endif
However, it looks like not all MPI implementations have these defined. Some
specify them as 'parameters' in which case I do not believe the above will
work.
ideas?
All the best
Ross
/\
\/
|\oss Walker
| Assistant Research Professor |
| San Diego Supercomputer Center |
| Tel: +1 858 822 0854 | EMail:- ross.rosswalker.co.uk |
|
http://www.rosswalker.co.uk |
http://www.wmd-lab.org/ |
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Received on Thu Apr 15 2010 - 21:30:02 PDT
