Developer Reference

  • 2020.2
  • 07/15/2020
  • Public Content
Contents

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:
  • 1 = Set the BLACS message ID range
  • 11 = Number of rings for multiring broadcast topology to use
  • 12 = Number of branches for general tree broadcast topology to use
  • 13 = Number of rings for multiring combine topology to use
  • 14 = Number of branches for general tree combine topology to use
  • 15 = Force topologies to be repeatable or not
  • 16 = Force topologies to be heterogenous coherent or not
val
INTEGER
. Array of dimension (*). Indicates the value(s) the internals should be set to. The specific meanings depend on
what
values
, as discussed in Description below
.
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.

Product and Performance Information

1

Intel's compilers may or may not optimize to the same degree for non-Intel microprocessors for optimizations that are not unique to Intel microprocessors. These optimizations include SSE2, SSE3, and SSSE3 instruction sets and other optimizations. Intel does not guarantee the availability, functionality, or effectiveness of any optimization on microprocessors not manufactured by Intel. Microprocessor-dependent optimizations in this product are intended for use with Intel microprocessors. Certain optimizations not specific to Intel microarchitecture are reserved for Intel microprocessors. Please refer to the applicable product User and Reference Guides for more information regarding the specific instruction sets covered by this notice.

Notice revision #20110804