MPI_TESTSOME(3)

📦
version 5.0.10 · 7 versions
, in ubuntu stonking

🌸 MPI_TESTSOME(3) 🌸

okay so this is the Open MPI manual page for MPI_Testsome, and bestie, she is a main character 💅

👑 NAME 👑

MPI_Testsome — tests for completion of one or more previously initiated communications in a list ✨

🎀 SYNTAX 🎀

💖 C Syntax

#include <mpi.h>

int MPI_Testsome(int incount, MPI_Request array_of_requests[],
     int *outcount, int array_of_indices[],
     MPI_Status array_of_statuses[])

🌸 Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_TESTSOME(INCOUNT, ARRAY_OF_REQUESTS, OUTCOUNT,
             ARRAY_OF_INDICES, ARRAY_OF_STATUSES, IERROR)
     INTEGER INCOUNT, ARRAY_OF_REQUESTS(*)
     INTEGER OUTCOUNT, ARRAY_OF_INDICES(*)
     INTEGER ARRAY_OF_STATUSES(MPI_STATUS_SIZE,*), IERROR

🦋 Fortran 2008 Syntax

USE mpi_f08
MPI_Testsome(incount, array_of_requests, outcount, array_of_indices,
             array_of_statuses, ierror)
     INTEGER, INTENT(IN) :: incount
     TYPE(MPI_Request), INTENT(INOUT) :: array_of_requests(incount)
     INTEGER, INTENT(OUT) :: outcount, array_of_indices(*)
     TYPE(MPI_Status) :: array_of_statuses(*)
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

💜 INPUT PARAMETERS 💜

  • incount — the length of array_of_requests (an integer, obviously 🫶).
  • array_of_requests — your array of requests (array of handles).

💅 OUTPUT PARAMETERS 💅

  • outcount — how many requests actually completed (integer). the receipts 📋
  • array_of_indices — array of indices of the operations that completed (array of integers).
  • array_of_statuses — array of status objects for the operations that completed (array of status).
  • ierror — Fortran only: error status (integer).

✨ DESCRIPTION ✨

She behaves exactly like MPI_Waitsome except — and this is the whole vibe — she returns immediately. no blocking, no waiting, we are not standing outside the club 💀

She returns in outcount the number of requests from the list array_of_requests that have completed. Then she returns, in the first outcount locations of the array array_of_indices, the indices of these operations (the index is within the array array_of_requests; and heads up, the array is indexed from 0 in C and from 1 in Fortran 🙈). She also returns, in the first outcount locations of the array array_of_status, the status for these completed operations. If a request that completed was allocated by a nonblocking communication call, then it is deallocated, and the associated handle is set to MPI_REQUEST_NULL. clean up after yourself, periodt ✨

If no operation has completed, she returns outcount = 0. If there is no active handle in the list at all, she returns outcount = MPI_UNDEFINED.

Here's the tea: MPI_Testsome is a local operation, which returns immediately, whereas MPI_Waitsome blocks until a communication completes — but only if it was passed a list that contains at least one active handle. Both calls fulfill a fairness requirement: if a request for a receive repeatedly appears in a list of requests passed to MPI_Waitsome or MPI_Testsome, and a matching send has been posted, then the receive will eventually succeed unless the send is satisfied by another receive. send requests also fulfill this fairness requirement. iconic behaviour, no cap 👑

Errors that occur during the execution of MPI_Testsome are handled as for MPI_Waitsome.

And if your application doesn't need to examine the array_of_statuses field, you can save resources by using the predefined constant MPI_STATUSES_IGNORE — it can be used as a special value for the array_of_statuses argument. free real estate 🍓

📝 NOTES 📝

The use of MPI_Testsome is likely to be more efficient than the use of MPI_Testany. Why? Because the former returns information on all completed communications, whereas with the latter, a new call is required for each communication that completes. batch it, don't do it one by one bestie 😭

A server with multiple clients can use MPI_Waitsome so as not to starve any client. Clients send messages to the server with service requests. The server calls MPI_Waitsome with one receive request for each client, then handles all receives that have completed. But if a call to MPI_Waitany is used instead, then one client could starve while requests from another client always sneak in first. not the favouritism 💀

🚨 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 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. so many handlers, she's got a whole contact list 📱

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

  • MPI_ERRORS_ARE_FATAL — causes the program to abort all connected MPI processes. she said everybody's coming down with me 💀
  • 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, 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, aborts only the local process.
  • MPI_ERRORS_RETURN — returns an error code to the application. polite queen 🫶

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. fr fr, don't assume she recovers 🙈

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.

For each invocation of MPI_Testsome, if one or more requests generate an MPI error, only the first 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, all requests that generate an error will have a relevant error code set in the corresponding status.MPI_ERROR field (unless MPI_STATUSES_IGNORE was used). so like, they all get their error code, but only one gets the moment 😭

If the invoked error handler allows MPI_Testsome to return to the caller, the value MPI_ERR_IN_STATUS will be returned in the C and Fortran bindings.

🌈 See also:

  • MPI_Comm_set_errhandler
  • MPI_File_set_errhandler
  • MPI_Test
  • MPI_Testall
  • MPI_Testany
  • MPI_Wait
  • MPI_Waitall
  • MPI_Waitany
  • MPI_Waitsome
  • MPI_Win_set_errhandler

2003-2026, The Open MPI Community

and that's the whole page bestie!! this drop is from the Open MPI girlies, dated Sep 10, 2026 — MPI_TESTSOME(3), slay, bye 💖✨🦋💅

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