[gmx-developers] MPI_sendrecv and specific timing

[Nathan Moore]

Fellows,

So I've included the revised version of move_f and move_x from the old
source revision (1.8) of mvxvf.c.  I notice a slight speedup in the dpcc
benchmark, but signifigant time remains in the MPI Sendrecv command -
(about 10% of execution wall time).  The only other place in the source I
can find MPI_Sendrecv is in stat.c's moveit function, used via #define
with the MX( macro.

Should moveit really be eating up 10% of execution?

regards,

Nathan Moore

timing, dpcc, 5000 timesteps, np=64, in seconds, median processor
statistics below:

version 3.2

MPI Routine                  #calls     avg. bytes      time(sec)
-----------------------------------------------------------------
MPI_Comm_size                     1            0.0          0.000
MPI_Comm_rank                     1            0.0          0.000
MPI_Send                        749        27628.6          0.214
MPI_Isend                    693883        32055.4          1.240
MPI_Recv                        749        27628.6         23.499
MPI_Irecv                    693883        32055.4          0.562
MPI_Sendrecv                 320190        45696.0        195.866
MPI_Wait                    2028146            0.0        238.088

v 3.2 with collective move_f and move_x

MPI Routine                  #calls     avg. bytes      time(sec)
-----------------------------------------------------------------
MPI_Comm_size                     1            0.0          0.000
MPI_Comm_rank                     1            0.0          0.000
MPI_Send                        749        27628.6          0.218
MPI_Isend                    693883        32055.4          1.301
MPI_Recv                        749        27628.6         14.872
MPI_Irecv                    693883        32055.4          0.484
MPI_Sendrecv                 160158        45696.0        108.985
MPI_Wait                    1708082            0.0        245.779
MPI_Allgatherv                 5001        45696.0         68.676