MPI\_MRECV(3) Open MPI MPI\_MRECV(3)

MPI\_Mrecv — Blocking receive for a matched message

# [SYNTAX](#SYNTAX)

## [C Syntax](#C_Syntax)

```
#include <mpi.h>
int MPI_Mrecv(void *buf, int count, MPI_Datatype type,


     MPI_Message *message, MPI_Status *status)
```

## [Fortran Syntax](#Fortran_Syntax)

```
USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_MRECV(BUF, COUNT, DATATYPE, MESSAGE, STATUS, IERROR)


     <type>  BUF(*)


     INTEGER COUNT, DATATYPE, MESSAGE


     INTEGER STATUS(MPI_STATUS_SIZE), IERROR
```

## [Fortran 2008 Syntax](#Fortran_2008_Syntax)

```
USE mpi_f08
MPI_Mrecv(buf, count, datatype, message, status, ierror)


     TYPE(*), DIMENSION(..) :: buf


     INTEGER, INTENT(IN) :: count


     TYPE(MPI_Datatype), INTENT(IN) :: datatype


     TYPE(MPI_Message), INTENT(INOUT) :: message


     TYPE(MPI_Status) :: status


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

# [INPUT PARAMETERS](#INPUT_PARAMETERS)

- **count**: Number of elements to receive (nonnegative integer).
- **datatype**: Datatype of each send buffer element (handle).
- **message**: Message (handle).

# [OUTPUT PARAMETERS](#OUTPUT_PARAMETERS)

- **buf**: Initial address of receive buffer (choice).
- **status**: Status object (status).
- **ierror**: Fortran only: Error status (integer).

# [DESCRIPTION](#DESCRIPTION)

The functions MPI\_Mrecv and MPI\_Imrecv &lt;#mpi-imrecv&gt; receive messages that have been previously matched by a matching probe.

If MPI\_Mrecv is called with **MPI\_MESSAGE\_NULL** as the message argument, the call returns immediately with the *status* object set to *source* = **MPI\_PROC\_NULL**, *tag* = **MPI\_ANY\_TAG**, and *count* = 0, as if a receive from **MPI\_PROC\_NULL** was issued.

If your application does not 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.

# [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.

Note that per the “Return Status” section in the “Point-to-Point Communication” chapter in the MPI Standard &lt;https://www.mpi-forum.org/docs/&gt;, MPI errors on messages received by MPI\_Mrecv 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\_Mrecv 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\_Mprobe &lt;#mpi-mprobe&gt;
- MPI\_Improbe &lt;#mpi-improbe&gt;
- MPI\_Probe &lt;#mpi-probe&gt;
- MPI\_Iprobe &lt;#mpi-iprobe&gt;
- MPI\_Imrecv &lt;#mpi-imrecv&gt;
- MPI\_Cancel &lt;#mpi-cancel&gt;

# [Copyright](#Copyright)

2003-2026, The Open MPI Community

October 30, 2026

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Document: MPI_Mrecv(3) from openmpi-cuda-13.0 5.0.11-r1 (Chainguard OS)
Source: https://github.com/open-mpi/ompi