MPI\_QUERY\_THREAD(3) Open MPI MPI\_QUERY\_THREAD(3)

MPI\_Query\_thread — Returns the current level of thread support

# [SYNTAX](#SYNTAX)

## [C Syntax](#C_Syntax)

```
#include <mpi.h>
int MPI_Query_thread(int *provided)
```

## [Fortran Syntax](#Fortran_Syntax)

```
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_QUERY_THREAD(PROVIDED, IERROR)


     INTEGER PROVIDED, IERROR
```

## [Fortran 2008 Syntax](#Fortran_2008_Syntax)

```
USE mpi_f08
MPI_Query_thread(provided, ierror)


     INTEGER, INTENT(OUT) :: provided


     INTEGER, OPTIONAL, INTENT(OUT) :: ierror
```

# [OUTPUT PARAMETERS](#OUTPUT_PARAMETERS)

- **provided**: C/Fortran only: Level of thread support (integer).
- **ierror**: Fortran only: Error status (integer).

# [DESCRIPTION](#DESCRIPTION)

This routine returns in *provided* the current level of thread support. If MPI was initialized by a call to MPI\_Init\_thread &lt;#mpi-init-thread&gt;, *provided* will have the same value as was returned by that function.

The possible values of *provided* are as follows:

[**MPI\_THREAD\_SINGLE**](#MPI_THREAD_SINGLE)

Only one thread may execute.

[**MPI\_THREAD\_FUNNELED**](#MPI_THREAD_FUNNELED)

If the process is multithreaded, only the thread that called MPI\_Init\[\_thread] may make MPI calls.

[**MPI\_THREAD\_SERIALIZED**](#MPI_THREAD_SERIALIZED)

If the process is multithreaded, only one thread may make MPI library calls at one time.

[**MPI\_THREAD\_MULTIPLE**](#MPI_THREAD_MULTIPLE)

If the process is multithreaded, multiple threads may call MPI at once with no restrictions.

# [NOTES](#NOTES)

In Open MPI, *provided* is always MPI\_THREAD\_SINGLE, unless the program has been linked with the multithreaded library, in which case *provided* is MPI\_THREAD\_MULTIPLE.

# [ERRORS](#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 &lt;#mpi-init&gt;/MPI\_Init\_thread &lt;#mpi-init-thread&gt;, after MPI\_Finalize &lt;#mpi-finalize&gt;, 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 &lt;#mpi-comm-set-errhandler&gt; 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 &lt;#mpi-comm-spawn&gt;/MPI\_Comm\_spawn\_multiple &lt;#mpi-comm-spawn-multiple&gt;. 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.
- **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 &lt;#mpi-abort&gt; was called on that communicator. If called on a window or file, acts as if MPI\_Abort &lt;#mpi-abort&gt; 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.

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

- MPI\_Comm\_create\_errhandler &lt;#mpi-comm-create-errhandler&gt; then MPI\_Comm\_set\_errhandler &lt;#mpi-comm-set-errhandler&gt;
- MPI\_File\_create\_errhandler &lt;#mpi-file-create-errhandler&gt; then MPI\_File\_set\_errhandler &lt;#mpi-file-set-errhandler&gt;
- MPI\_Session\_create\_errhandler &lt;#mpi-session-create-errhandler&gt; then MPI\_Session\_set\_errhandler &lt;#mpi-session-set-errhandler&gt; or at MPI\_Session\_init &lt;#mpi-session-init&gt;
- MPI\_Win\_create\_errhandler &lt;#mpi-win-create-errhandler&gt; then MPI\_Win\_set\_errhandler &lt;#mpi-win-set-errhandler&gt;

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

See the MPI man page &lt;#open-mpi&gt; for a full list of MPI error codes &lt;#open-mpi-errors&gt;.

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

**See also:**

- MPI\_Init &lt;#mpi-init&gt;
- MPI\_Init\_thread &lt;#mpi-init-thread&gt;

# [Copyright](#Copyright)

2003-2026, The Open MPI Community

September 11, 2026

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Document: MPI_Query_thread(3) from openmpi-cuda-13.2 5.0.11-r0 (Chainguard OS)
Source: https://github.com/open-mpi/ompi