Purpose

PxGEMR2D copies the indicated (sub)matrix of A to the indicated (sub)matrix of B. A and B can have arbitrary block-cyclic distributions: they can be distributed across different process grids, have different blocking factors, etc.

Particular care must be taken when the process grid over which matrix A is distributed (call this context A) is disjoint from the process grid over which matrix B is distributed (call this context B). The general rules for which parameters need to be set are:

• All calling processes must have the correct M and N.
• Processes in context A must correctly define all parameters describing A.
• Processes in context B must correctly define all parameters describing B.
• Processes which are not members of context A must pass DESCA(CTXT_) = -1 and need not set other parameters describing A.
• Processes which are not members of context B must pass DESCB(CTXT_) = -1 and need not set other parameters describing B.