I Message Envelope Message envelope of an MPI message provides information on how to match sends to receives it consists of 3 parts Source or destination This argument is set to a rank in a communicator Destination is specified by the sending process and source is specified by the receiving process. Only messages coming from that source can be accepted by the receive call, but the receive can set source to MP/ ANY SOURCE to indicate that any source is acceptable Communicator The communicator specifies a group of processes to which both source and destination belong Tag The tag is an arbitrary number to help distinguish among messages. The tags specified by the sender and receiver must match, but the receiver can specify MPI_ ANY_ TAG to indicate that any tag is acceptable. For example, one tag value can be used for messages containing data and another tag value for messages containing status informationMessage Envelope • Message envelope of an MPI message provides information on how to match sends to receives. it consists of 3 parts: – Source or destination This argument is set to a rank in a communicator. Destination is specified by the sending process and source is specified by the receiving process. Only messages coming from that source can be accepted by the receive call, but the receive can set source to MPI_ANY_SOURCE to indicate that any source is acceptable. – Communicator The communicator specifies a group of processes to which both source and destination belong. – Tag The tag is an arbitrary number to help distinguish among messages. The tags specified by the sender and receiver must match, but the receiver can specify MPI_ANY_TAG to indicate that any tag is acceptable. For example, one tag value can be used for messages containing data and another tag value for messages containing status information