Developer Reference for Intel® oneAPI Math Kernel Library for C
blacs_set
Sets values that BLACS use for internal defaults.
Syntax
call blacs_set( icontxt, what, val )
Input Parameters
icontxt |
INTEGER. For values of what that are tied to a particular context, this parameter is the integer handle indicating the context. Otherwise, ignored. |
what |
INTEGER. Indicates what BLACS internal(s) should be set. Present values are:
|
val |
INTEGER. Array of dimension (*). Indicates the value(s) the internals should be set to. The specific meanings depend on what values. |
Description
This routine sets the BLACS internal defaults depending on what values:
- what = 1
-
Setting the BLACS message ID range.
If you wish to mix the BLACS with other message-passing packages, restrict the BLACS to a certain message ID range not to be used by the non-BLACS routines. The message ID range must be set before the first call to blacs_gridinit or blacs_gridmap. Subsequent calls will have no effect. Because the message ID range is not tied to a particular context, the parameter icontxt is ignored, and val is defined as:
VAL (input) INTEGER array of dimension (2)
VAL(1) : The smallest message ID (also called message type or message tag) the BLACS should use.
VAL(2) : The largest message ID (also called message type or message tag) the BLACS should use.
- what = 11
-
Set number of rings for TOP = 'M' (multiring broadcast).This quantity is tied to a context, so icontxt is used, and val is defined as:
VAL (input) INTEGER array of dimension (1)
VAL(1) : The number of rings for multiring topology to use.
- what = 12
-
Set number of branches for TOP = 'T' (general tree broadcast). This quantity is tied to a context, so icontxt is used, and val is defined as:
VAL (input) INTEGER array of dimension (1)
VAL(1) : The number of branches for general tree topology to use.
- what = 13
-
Set number of rings for TOP = 'M' (multiring combine).This quantity is tied to a context, so icontxt is used, and val is defined as:
VAL (input) INTEGER array of dimension (1)
VAL(1) : The number of rings for multiring topology to use.
- what = 14
-
Set number of branches for TOP = 'T' (general tree gather). This quantity is tied to a context, so icontxt is used, and val is defined as:
VAL (input) INTEGER array of dimension (1)
VAL(1) : The number of branches for general tree topology to use.
- what = 15
-
Force topologies to be repeatable or not (see Repeatability and Coherence for more information about repeatability).
VAL (input) INTEGER array of dimension (1)
VAL(1) = 0 (default)
Topologies are not required to be repeatable.
VAL(1) ≠ 0
All used topologies are required to be repeatable, which might degrade performance.
- what = 16
-
Force topologies to be heterogenous coherent or not (see Repeatability and Coherence for more information about coherence).
VAL (input) INTEGER array of dimension (1)
VAL(1) = 0 (default)
Topologies are not required to be heterogenous coherent.
VAL(1) ≠ 0
All used topologies are required to be heterogenous coherent, which might degrade performance.