Parameters Controlling Intel® MPI Benchmarks

Parameters controlling the default settings of the Intel® MPI Benchmarks are set by preprocessor definition in files IMB_settings.h (for IMB-MPI1 and IMB-EXT benchmarks) and IMB_settings_io.h (for IMB-IO benchmarks). Both include files have identical structure, but differ in the predefined parameter values.

To enable the optional mode, define the IMB_OPTIONAL parameter in the IMB_settings.h/IMB_settings_io.h. After you change the settings in the optional section, you need to recompile the Intel® MPI Benchmarks.

The following table describes the Intel MPI Benchmarks parameters and lists their values for the standard mode.

Parameter	Values in IMB_settings.h	Values in IMB_settings_io.h	Description
`USE_MPI_INIT_THREAD`	Not set	Not set	Set to initialize Intel® MPI Benchmarks by `MPI_Init_thread()` instead of `MPI_Init()`
`IMB_OPTIONAL`	Not set	Not set	Set to activate optional settings
`MINMSGLOG`	0	0	The second smallest data transfer size is `max(unit,2^MINMSGLOG` (the smallest size is always 0), where `unit=sizeof(float)` for reductions, `unit=1` for all other cases. You can override this parameter value using the `-msglog` flag.
`MAXMSGLOG`	22	24	The largest message size used is `2^MAXMSGLOG` You can override this parameter value using the `-msglog` flag.
`ITER_POLICY`	imode_dynamic		The policy used for calculating the number of iterations. You can override this parameter value using the `-iter_policy` or `-iter` flag.
`MSGSPERSAMPLE`	1000	50	The maximum repetition count for all IMB-MPI1 benchmarks. You can override this parameter value using the `-iter` flag.
`MSGS_NONAGGR`	100	10	The maximum repetition count for non-aggregate benchmarks (relevant only for `IMB-EXT`). You can override this parameter value using the `-time` flag.
`OVERALL_VOL`	40 Mbytes	16*1048576	For all sizes smaller than `OVERALL_VOL`, the repetition count is reduced so that not more than `OVERALL_VOL` bytes are processed all in all. This permits you to avoid unnecessary repetitions for large message sizes. Finally, the real repetition count for message size X is `MSGSPERSAMPLE (X=0)`, `max(1,min(MSGSPERSAMPLE,OVERALL_VOL/X)) (X>0)` Note that `OVERALL_VOL` does not restrict the size of the maximum data transfer. `2^MAXMSGLOG OVERALL_VOL.` You can override this parameter value using the `-mem` flag.
`SECS_PER_SAMPLE`	10		Number of iterations is dynamically set so that this number of run time seconds is not exceeded per message length.
`N_BARR`	2	2	Number of `MPI_Barrier` for synchronization.
`TARGET_CPU_SECS`	0.01 seconds	0.1 seconds	CPU seconds (as float) to run concurrently with nonblocking benchmarks (irrelevant for IMB-MPI1)

In the example below, the IMB_settings_io.h. file has the IMB_OPTIONAL parameter enabled, so that user-defined parameters are used. I/O sizes of 32 and 64 MB, and a smaller repetition count are selected, extending the standard mode tables. You can modify the optional values as required.

#define FILENAME IMB_out
#define IMB_OPTIONAL
#ifdef IMB_OPTIONAL
#define MINMSGLOG  25
#define MAXMSGLOG  26
#define MSGSPERSAMPLE  10
#define MSGS_NONAGGR  10
#define OVERALL_VOL  16*1048576
#define SECS_PER_SAMPLE  10
#define TARGET_CPU_SECS 0.1 /* unit seconds */
#define N_BARR   2
#else
/*Do not change anything below this line*/
#define MINMSGLOG  0
#define MAXMSGLOG  24
#define MSGSPERSAMPLE  50
#define MSGS_NONAGGR  10
#define OVERALL_VOL 16*1048576
#define TARGET_CPU_SECS  0.1 /* unit seconds */
#define N_BARR   2
#endif

If IMB_OPTIONAL is deactivated, Intel MPI Benchmarks uses the default standard mode values.