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.TH "MPI_WAITALL" "3" "May 30, 2025" "" "Open MPI"
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.sp
\fI\%MPI_Waitall\fP — Waits for all given communications to complete.
.SH SYNTAX
.SS C Syntax
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
#include <mpi.h>

int MPI_Waitall(int count, MPI_Request array_of_requests[],
     MPI_Status *array_of_statuses)
.ft P
.fi
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.SS Fortran Syntax
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.INDENT 3.5
.sp
.nf
.ft C
USE MPI
! or the older form: INCLUDE \(aqmpif.h\(aq
MPI_WAITALL(COUNT, ARRAY_OF_REQUESTS, ARRAY_OF_STATUSES, IERROR)
     INTEGER COUNT, ARRAY_OF_REQUESTS(*)
     INTEGER ARRAY_OF_STATUSES(MPI_STATUS_SIZE,*), IERROR
.ft P
.fi
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.SS Fortran 2008 Syntax
.INDENT 0.0
.INDENT 3.5
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.nf
.ft C
USE mpi_f08
MPI_Waitall(count, array_of_requests, array_of_statuses, ierror)
     INTEGER, INTENT(IN) :: count
     TYPE(MPI_Request), INTENT(INOUT) :: array_of_requests(count)
     TYPE(MPI_Status) :: array_of_statuses(*)
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror
.ft P
.fi
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.SH INPUT PARAMETERS
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.IP \(bu 2
\fBcount\fP: Lists length (integer).
.IP \(bu 2
\fBarray_of_requests\fP: Array of requests (array of handles).
.UNINDENT
.SH OUTPUT PARAMETERS
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.IP \(bu 2
\fBarray_of_statuses\fP: Array of status objects (array of status).
.IP \(bu 2
\fBierror\fP: Fortran only: Error status (integer).
.UNINDENT
.SH DESCRIPTION
.sp
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.
.sp
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. \fI\%MPI_Waitall\fP with an array of
length 1 is equivalent to \fI\%MPI_Wait\fP\&.
.sp
When one or more of the communications completed by a call to
\fI\%MPI_Waitall\fP fail, it is desirable to return specific information on each
communication. The function \fI\%MPI_Waitall\fP 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 \fI\%MPI_Waitall\fP 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.
.sp
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.
.SH ERRORS
.sp
Almost all MPI routines return an error value; C routines as the return result
of the function and Fortran routines in the last argument.
.sp
Before the error value is returned, the current MPI error handler associated
with the communication object (e.g., communicator, window, file) is called.
If no communication object is associated with the MPI call, then the call is
considered attached to MPI_COMM_SELF and will call the associated MPI error
handler. When MPI_COMM_SELF is not initialized (i.e., before
\fI\%MPI_Init\fP/\fI\%MPI_Init_thread\fP, after \fI\%MPI_Finalize\fP, or when using the Sessions
Model exclusively) the error raises the initial error handler. The initial
error handler can be changed by calling \fI\%MPI_Comm_set_errhandler\fP on
MPI_COMM_SELF when using the World model, or the mpi_initial_errhandler CLI
argument to mpiexec or info key to \fI\%MPI_Comm_spawn\fP/\fI\%MPI_Comm_spawn_multiple\fP\&.
If no other appropriate error handler has been set, then the MPI_ERRORS_RETURN
error handler is called for MPI I/O functions and the MPI_ERRORS_ABORT error
handler is called for all other MPI functions.
.sp
Open MPI includes three predefined error handlers that can be used:
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.IP \(bu 2
\fBMPI_ERRORS_ARE_FATAL\fP
Causes the program to abort all connected MPI processes.
.IP \(bu 2
\fBMPI_ERRORS_ABORT\fP
An error handler that can be invoked on a communicator,
window, file, or session. When called on a communicator, it
acts as if \fI\%MPI_Abort\fP was called on that communicator. If
called on a window or file, acts as if \fI\%MPI_Abort\fP was called
on a communicator containing the group of processes in the
corresponding window or file. If called on a session,
aborts only the local process.
.IP \(bu 2
\fBMPI_ERRORS_RETURN\fP
Returns an error code to the application.
.UNINDENT
.sp
MPI applications can also implement their own error handlers by calling:
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.IP \(bu 2
\fI\%MPI_Comm_create_errhandler\fP then \fI\%MPI_Comm_set_errhandler\fP
.IP \(bu 2
\fI\%MPI_File_create_errhandler\fP then \fI\%MPI_File_set_errhandler\fP
.IP \(bu 2
\fI\%MPI_Session_create_errhandler\fP then \fI\%MPI_Session_set_errhandler\fP or at \fI\%MPI_Session_init\fP
.IP \(bu 2
\fI\%MPI_Win_create_errhandler\fP then \fI\%MPI_Win_set_errhandler\fP
.UNINDENT
.sp
Note that MPI does not guarantee that an MPI program can continue past
an error.
.sp
See the \fI\%MPI man page\fP for a full list of \fI\%MPI error codes\fP\&.
.sp
See the Error Handling section of the MPI\-3.1 standard for
more information.
.sp
For each invocation of \fI\%MPI_Waitall\fP, if one or more requests
generate an MPI error, only the \fIfirst\fP MPI request that caused an
error will be passed to its corresponding error handler. No other
error handlers will be invoked (even if multiple requests generated
errors). However, \fIall\fP requests that generate an error will have a
relevant error code set in the corresponding \fBstatus.MPI_ERROR\fP
field (unless \fBMPI_STATUSES_IGNORE\fP was used).
.sp
If the invoked error handler allows \fI\%MPI_Waitall\fP to return to
the caller, the value \fBMPI_ERR_IN_STATUS\fP will be returned in the C
and Fortran bindings.
.sp
\fBSEE ALSO:\fP
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.INDENT 3.5
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.IP \(bu 2
\fI\%MPI_Comm_set_errhandler\fP
.IP \(bu 2
\fI\%MPI_File_set_errhandler\fP
.IP \(bu 2
\fI\%MPI_Test\fP
.IP \(bu 2
\fI\%MPI_Testall\fP
.IP \(bu 2
\fI\%MPI_Testany\fP
.IP \(bu 2
\fI\%MPI_Testsome\fP
.IP \(bu 2
\fI\%MPI_Wait\fP
.IP \(bu 2
\fI\%MPI_Waitany\fP
.IP \(bu 2
\fI\%MPI_Waitsome\fP
.IP \(bu 2
\fI\%MPI_Win_set_errhandler\fP
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.SH COPYRIGHT
2003-2025, The Open MPI Community
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