Gets values that BLACS use for internal defaults.
call blacs_get( icontxt, what, val )
icontxt |
INTEGER. On 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 returned in val. Present options are:
|
val |
INTEGER. The value of the BLACS internal. |
This routine gets the values that the BLACS are using for internal defaults. Some values are tied to a BLACS context, and some are more general. The most common use is in retrieving a default system context for input into blacs_gridinit or blacs_gridmap.
Some systems, such as MPI*, supply their own version of context. For those users who mix system code with BLACS code, a BLACS context should be formed in reference to a system context. Thus, the grid creation routines take a system context as input. If you wish to have strictly portable code, you may use blacs_get to retrieve a default system context that will include all available processes. This value is not tied to a BLACS context, so the parameter icontxt is unused.
blacs_get returns information on three quantities that are tied to an individual BLACS context, which is passed in as icontxt. The information that may be retrieved is:
The handle of the system context upon which this BLACS context was defined
The number of rings for TOP = 'M' (multiring broadcast)
The number of branches for TOP = 'T' (general tree broadcast/general tree gather).
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