Description

S3L_thread_comm_setup establishes the appropriate internal MPI communicators and data for thread-safe operation of S3L functions. It should be called from each thread in which S3L functions will be used.

Only S3L_init can be called before S3L_thread_comm_setup.

The argument comm specifies an MPI communicator, which should be congruent with, but not identical to, MPI_COMM_WORLD.

A unique communicator must be used for each thread or set of cooperating threads. The term "cooperating threads" refers to a set of threads that will be working on the same data. For example, one thread can initialize a random number generator, obtain a setup ID, and pass this to a fellow cooperating thread, which will then use the random number generator.

In such cases, the user must ensure that the threads within a cooperating set are properly synchronized.

A unique communicator is required because S3L performs internal communications. For example, when S3L_mat_mult is called from a multithreaded program, the thread on one node needs to communicate with the appropriate thread on another node. This can be done only if a communicator that is unique to these threads has been previously defined and passed to the communications routines within S3L.

S3L_thread_comm_setup need not be invoked if S3L functions are called from only one thread in the user's program.

S3L_thread_comm_setup is useful when a user performs explicit multithreading via threads library functions. Since threads library functions are not available in F77, the F77 interface for S3L_thread_comm_setup is not provided.