Measuring Pure Communication Time#
To measure pure execution time of nonblocking collective operations, use
the _pure flavor of the IMB-NBC benchmarks. The benchmark
methodology is consistent with the one used for regular collective
operations:
Each rank performs the predefined amount of iterations and calculates the mean value.
The basic MPI data type for all messages is
MPI_BYTEfor pure data movement functions andMPI_FLOATfor reductions.If the operation requires the root process to be specified, the root process is selected round-robin through iterations.
These benchmarks are not included into the default list of IMB-NBC
benchmarks. To run a benchmark, specify the particular benchmark name or
use the –include command-line parameter. For example:
$ mpirun -np 2 IMB-NBC Ialltoall_pure
$ mpirun -np 2 IMB-NBC -include Iallgather_pure Ialltoall_pure
Displaying Results#
Pure nonblocking collective benchmarks show bare timing values. Since execution time may vary for different ranks, three timing values are shown: maximum, minimum, and the average time among all the ranks participating in the benchmark measurements.
See Also