Blocks until all communication operations associated with active handles in the list complete, and returns the status of all these operations (this includes the case where no handle in the list is active). Both arrays have the same number of valid entries. The ith entry in array_of_statuses is set to the return status of the ith operation. Requests that were created by nonblocking communication operations are deallocated, and the corresponding handles in the array are set to MPI_REQUEST_NULL. The list may contain null or inactive handles. The call sets to empty the status of each such entry.
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The error-free execution of MPI_Waitall(count, array_of_requests, array_of_statuses) has the same effect as the execution of MPI_Wait(&array_of_request[i], &array_of_statuses[i]), for i=0,...,count-1, in some arbitrary order. MPI_Waitall with an array of length 1 is equivalent to MPI_Wait.
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When one or more of the communications completed by a call to MPI_Waitall fail, it is desirable to return specific information on each communication. The function MPI_Waitall will return in such case the error code MPI_ERR_IN_STATUS and will set the error field of each status to a specific error code. This code will be MPI_SUCCESS if the specific communication completed; it will be another specific error code if it failed; or it can be MPI_ERR_PENDING if it has neither failed nor completed. The function MPI_Waitall will return MPI_SUCCESS if no request had an error, or will return another error code if it failed for other reasons (such as invalid arguments). In such cases, it will not update the error fields of the statuses.
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If your application does not need to examine the \fIarray_of_statuses\fP field, you can save resources by using the predefined constant MPI_STATUSES_IGNORE can be used as a special value for the \fIarray_of_statuses\fP argument.
