mpi.wait: Nonblocking completion operations

Description

mpi.cancel cancels a nonblocking send or receive request.

mpi.test.cancelled tests if mpi.cancel cancels or not.

wait, waitall, waitany, and waitsome are used to complete nonblocking send or receive requests. They are not local.

test, testall, testany, and testsome are used to complete nonblocking send and receive requests. They are local.

Usage

mpi.cancel(request)
mpi.test.cancelled(status=0)
mpi.test(request, status=0)
mpi.testall(count)
mpi.testany(count, status=0)
mpi.testsome(count)
mpi.wait(request, status=0)
mpi.waitall(count)
mpi.waitany(count, status=0)
mpi.waitsome(count)

Value

mpi.cancel returns no value.

mpi.test.cancelled returns TRUE if a nonblocking call is cancelled; FALSE otherwise.

mpi.wait returns no value. Instead status contains information that can be retrieved by mpi.get.count and mpi.get.sourcetag.

mpi.test returns TRUE if a request is complete; FALSE otherwise. If TRUE, it is the same as mpi.wait.

mpi.waitany returns which request (index) has been completed. In addition, status contains information that can be retrieved by mpi.get.count and mpi.get.sourcetag.

mpi.testany returns a list: index--- request index; flag---TRUE if a request is complete; FALSE otherwise (index is no use in this case). If flag is TRUE, it is the same as mpi.waitany.

mpi.waitall returns no value. Instead statuses 0, 1, ..., count-1 contain corresponding information that can be retrieved by mpi.get.count and mpi.get.sourcetag.

mpi.testall returns TRUE if all requests are complete; FALSE otherwise. If TRUE, it is the same as mpi.waitall.

mpi.waitsome returns a list: count--- number of requests that have been completed; indices---an integer vector of size count of those completed request numbers (in 0, 1 ,..., count-1). In addition, statuses 0, 1, ..., count-1 contain corresponding information that can be retrieved by mpi.get.count and mpi.get.sourcetag.

mpi.testsome is the same as mpi.waitsome except that count may be 0 and in this case indices is no use.

Arguments

count: total number of nonblocking operations.
request: a request number.
status: a status number.

Author

Hao Yu

Details

mpi.wait and mpi.test are used to complete a nonblocking send and receive request: use the same request number by mpi.isend or mpi.irecv. Once completed, the associated request is set to MPI_REQUEST_NULL and status contains information such as source, tag, and length of message.

If multiple nonblocking sends or receives are initiated, the following calls are more efficient. Make sure that request numbers are used consecutively as request=0, request=1, request=2, etc. In this way, the following calls can find request information in system memory.

mpi.waitany and mpi.testany are used to complete one out of several requests.

mpi.waitall and mpi.testall are used to complete all requests.

mpi.waitsome and mpi.testsome are used to complete all enabled requests.

References

https://www.open-mpi.org/