2.2.3 Template inquiry routines

  Rather than accessing the data structure that encodes the template directly, the library provides inquiry routines, which can be used to query information about the mesh of nodes and the distribution of the template. The general rule is that all template inquiry routines start with PLA_Temp_ followed by the name of the field required.

In order to perform explicit communication using MPI, a routine may need access to the communicator describing all nodes in which the matrices and vectors exist. To gain access to information about this communicator PLAPACK provides the call

We also provide separate calls to extract each individual piece of information:

Note: The communicator returned is not the same as the communicator used to initialize PLAPACK. Notice that PLAPACK inherently orders the nodes in   column-major order. Since MPI orders nodes in row-major order, a new one-dimensional communicator, which describes the same nodes but in the new order, is created as part of the template creation process. It is information about this communicator that is queried by the above calls.

Frequently, communication occurs only within a row or column of nodes. For this purpose, we provide inquiry routines that return the communicator and related information for the row and column of nodes in which the calling node is a member:

As for the PLA_Temp_comm_all_info call, we also provide separate calls to each individual piece of information:

and

One can recover the   distribution blocking size used to create the template by calling

 

Indexing within a routine may be affected by the choice to start indexing into arrays at 0 or 1 . Recovering this information is facilitated by