MPIANYSOURCE

MPIANYSOURCE is the predefined constant in the Message Passing Interface (MPI) used as the source parameter in receive operations to indicate that a message may be received from any process within the communicator. The canonical name in the MPI standard is MPI_ANY_SOURCE; MPIANYSOURCE is an informal concatenation sometimes used in documentation or code comments.

It is most commonly used with receive functions such as MPI_Recv and MPI_Irecv. It can be combined with MPI_ANY_TAG to receive messages regardless of origin or tag. If both source and tag use MPI_ANY*, any message on the communicator is eligible for reception.

On completion, the actual sender and tag are returned in the status object, typically status.MPI_SOURCE and status.MPI_TAG. This allows the receiver to distinguish between messages. Using MPI_ANY_SOURCE introduces nondeterminism when multiple messages are ready, so message ordering is not guaranteed unless additional synchronization is used.

It is part of the MPI standard since MPI-1 and is supported by major implementations such as MPICH, Open MPI, and Intel MPI. It is widely used in dynamic task allocation and asynchronous communication patterns, but programmers should consider potential race conditions and ensure that program semantics account for possible variations in message arrival. See also MPI_ANY_TAG and the MPI_STATUS information returned after receives.