MPI_TESTANY(3)

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version 5.0.10 · 7 versions

💖 MPI_TESTANY 💖

Okay bestie, welcome to MPI_TESTANY(3), straight outta the Open MPI manual. It's giving "I just want to know if one of my requests is done." Let's get into it. 🦋

🌸 NAME 🌸

MPI_Testany — tests for completion of any one previously initiated communication in a list. Just one. Whoever finishes first gets the spotlight. ✨

👑 SYNTAX 👑

C Syntax

#include <mpi.h>

int MPI_Testany(int count, MPI_Request array_of_requests[],
     int *index, int *flag, MPI_Status *status)

Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_TESTANY(COUNT, ARRAY_OF_REQUESTS, INDEX, FLAG, STATUS, IERROR)
     LOGICAL FLAG
     INTEGER COUNT, ARRAY_OF_REQUESTS(*), INDEX
     INTEGER STATUS(MPI_STATUS_SIZE), IERROR

Fortran 2008 Syntax

USE mpi_f08
MPI_Testany(count, array_of_requests, index, flag, status, ierror)
     INTEGER, INTENT(IN) :: count
     TYPE(MPI_Request), INTENT(INOUT) :: array_of_requests(count)
     INTEGER, INTENT(OUT) :: index
     LOGICAL, INTENT(OUT) :: flag
     TYPE(MPI_Status) :: status
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

🎀 INPUT PARAMETERS 🎀

count — list length (integer). How many requests are we eyeing up, bestie.
array_of_requests — array of requests (array of handles). The whole squad of requests you're checking on.

🫶 OUTPUT PARAMETERS 🫶

index — index of the operation that completed, or MPI_UNDEFINED if none completed (integer). Your winner's seat number, or a big fat "nobody showed up."
flag — true if one of the operations is complete (logical). The yassss/nope indicator.
status — status object (status). The receipts.
ierror — Fortran only: error status (integer). Fortran's little error notecard.

💅 DESCRIPTION 💅

So, MPI_Testany tests for completion of either one or none of the operations associated with active handles.

In the former case — one of them finished, slay — it returns flag = true, returns in index the index of this request in the array, and returns in status the status of that operation. And if that request was allocated by a nonblocking communication call, then the request is deallocated and the handle is set to MPI_REQUEST_NULL. Cleanup queen. 🧹

Heads up on indexing, because this trips people up fr fr: the array is indexed from 0 in C, and from 1 in Fortran.

In the latter case (no operation completed, rip), it returns flag = false, returns a value of MPI_UNDEFINED in index, and status is undefined. Don't go reading it, okay? It's not real. 🙈

The array may contain null or inactive handles — that's totally allowed. And if the array contains no active handles, then the call returns immediately with flag = true, index = MPI_UNDEFINED, and an empty status. Instant. No waiting. Periodt.

If the array of requests does contain active handles, then the execution of

MPI_Testany(count, array_of_requests, index, status)

has the same effect as the execution of

MPI_Test(&array_of_requests[i], flag, status)

for i=0,1,…,count-1, in some arbitrary order, until one call returns flag = true, or all of them fail.

In the former case, index is set to the last value of i.
In the latter case, it's set to MPI_UNDEFINED.

Also, MPI_Testany with an array containing one active entry is equivalent to MPI_Test. Tiny squad, same energy. ✨

And if your application doesn't need to examine the status field, you can save resources by using the predefined constant MPI_STATUS_IGNORE as a special value for the status argument. Skipping the receipts = less to carry. 💅

💀 ERRORS 💀

Almost all MPI routines return an error value — C routines as the return result of the function, and Fortran routines in the last argument.

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 MPI_Init / MPI_Init_thread, after MPI_Finalize, or when using the Sessions Model exclusively), the error raises the initial error handler. The initial error handler can be changed by calling MPI_Comm_set_errhandler on MPI_COMM_SELF when using the World model, or the mpi_initial_errhandler CLI argument to mpiexec, or the info key to MPI_Comm_spawn / MPI_Comm_spawn_multiple. 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.

Open MPI includes three predefined error handlers that can be used:

MPI_ERRORS_ARE_FATAL — causes the program to abort all connected MPI processes. Everybody out. 😭
MPI_ERRORS_ABORT — an error handler that can be invoked on a communicator, window, file, or session. When called on a communicator, it acts as if MPI_Abort was called on that communicator. If called on a window or file, it acts as if MPI_Abort was called on a communicator containing the group of processes in the corresponding window or file. If called on a session, it aborts only the local process.
MPI_ERRORS_RETURN — returns an error code to the application. Polite of it.

MPI applications can also implement their own error handlers by calling:

MPI_Comm_create_errhandler then MPI_Comm_set_errhandler
MPI_File_create_errhandler then MPI_File_set_errhandler
MPI_Session_create_errhandler then MPI_Session_set_errhandler or at MPI_Session_init
MPI_Win_create_errhandler then MPI_Win_set_errhandler

Note that MPI does not guarantee that an MPI program can continue past an error. 🫠

See the MPI man page for a full list of MPI error codes.

See the Error Handling section of the MPI-3.1 standard for more information.

And here's a spicy lil' note: per the "Return Status" section in the "Point-to-Point Communication" chapter in the MPI Standard, MPI errors on requests passed to MPI_Testany do not set the status.MPI_ERROR field in the returned status. The error code is always passed to the back-end error handler and may be passed back to the caller through the return value of MPI_Testany if the back-end error handler returns it. The pre-defined MPI error handler MPI_ERRORS_RETURN exhibits this behavior, for example.

🌈 SEE ALSO 🌈

MPI_Comm_set_errhandler
MPI_File_set_errhandler
MPI_Test
MPI_Testall
MPI_Testsome
MPI_Wait
MPI_Waitall
MPI_Waitany
MPI_Waitsome
MPI_Win_set_errhandler

📜 COPYRIGHT 📜

Okay that's the whole page, bestie, you ate. 🍓 This iconic lil' manual page MPI_TESTANY(3) was last touched on Sep 10, 2026 — go forth and test exactly one request at a time, no cap. 💜🦋✨

📦 where this page comes from

ubuntu stonking: openmpi-doc 5.0.10-6 · other
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash on 2026-11-03: a language model's rewrite of the original, under its terms