MPI\_IMPROBE(3) Open MPI MPI\_IMPROBE(3) MPI\_Improbe — Non-blocking matched probe for a message. # [SYNTAX](#SYNTAX) ## [C Syntax](#C_Syntax) ``` #include int MPI_Improbe(int source, int tag, MPI_Comm comm, int *flag, MPI_Message *message, MPI_Status *status) ``` ## [Fortran Syntax](#Fortran_Syntax) ``` USE MPI ! or the older form: INCLUDE 'mpif.h' MPI_IMPROBE(SOURCE, TAG, COMM, FLAG, MESSAGE, STATUS, IERROR) LOGICAL FLAG INTEGER SOURCE, TAG, COMM, MESSAGE INTEGER STATUS(MPI_STATUS_SIZE), IERROR ``` ## [Fortran 2008 Syntax](#Fortran_2008_Syntax) ``` USE mpi_f08 MPI_Improbe(source, tag, comm, flag, message, status, ierror) INTEGER, INTENT(IN) :: source, tag TYPE(MPI_Comm), INTENT(IN) :: comm INTEGER, INTENT(OUT) :: flag TYPE(MPI_Message), INTENT(OUT) :: message TYPE(MPI_Status) :: status INTEGER, OPTIONAL, INTENT(OUT) :: ierror ``` # [INPUT PARAMETERS](#INPUT_PARAMETERS) - **source**: Source rank or **MPI\_ANY\_SOURCE** (integer). - **tag**: Tag value or **MPI\_ANY\_TAG** (integer). - **comm**: Communicator (handle). # [OUTPUT PARAMETERS](#OUTPUT_PARAMETERS) - **flag**: Flag (logical). - **message**: Message (handle). - **status**: Status object (status). - **ierror**: Fortran only: Error status (integer). # [DESCRIPTION](#DESCRIPTION) Like MPI\_Probe <#mpi-probe> and MPI\_Iprobe <#mpi-iprobe>, the MPI\_Mprobe <#mpi-mprobe> and MPI\_Improbe operations allow incoming messages to be queried without actually receiving them, except that MPI\_Mprobe <#mpi-mprobe> and MPI\_Improbe provide a mechanism to receive the specific message that was matched regardless of other intervening probe or receive operations. This gives the application an opportunity to decide how to receive the message, based on the information returned by the probe. In particular, the application may allocate memory for the receive buffer according to the length of the probed message. A matching probe with **MPI\_PROC\_NULL** as *source* returns *flag* = true, *message* = **MPI\_MESSAGE\_NO\_PROC**, and the *status* object returns source ^ **MPI\_PROC\_NULL**, tag ^ **MPI\_ANY\_TAG**, and count ^ 0. MPI\_Iprobe <#mpi-iprobe> returns a true value in *flag* if a message has been matched and can be received by passing the *message* handle to the MPI\_Mrecv <#mpi-mrecv> or MPI\_Imrecv <#mpi-imrecv> functions, provided the *source* was not **MPI\_PROC\_NULL**. # [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 <#mpi-init>/MPI\_Init\_thread <#mpi-init-thread>, after MPI\_Finalize <#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 <#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>/MPI\_Comm\_spawn\_multiple <#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. - **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 <#mpi-abort> was called on that communicator. If called on a window or file, acts as if MPI\_Abort <#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. MPI applications can also implement their own error handlers by calling: - MPI\_Comm\_create\_errhandler <#mpi-comm-create-errhandler> then MPI\_Comm\_set\_errhandler <#mpi-comm-set-errhandler> - MPI\_File\_create\_errhandler <#mpi-file-create-errhandler> then MPI\_File\_set\_errhandler <#mpi-file-set-errhandler> - MPI\_Session\_create\_errhandler <#mpi-session-create-errhandler> then MPI\_Session\_set\_errhandler <#mpi-session-set-errhandler> or at MPI\_Session\_init <#mpi-session-init> - MPI\_Win\_create\_errhandler <#mpi-win-create-errhandler> then MPI\_Win\_set\_errhandler <#mpi-win-set-errhandler> Note that MPI does not guarantee that an MPI program can continue past an error. See the MPI man page <#open-mpi> for a full list of MPI error codes <#open-mpi-errors>. See the Error Handling section of the MPI-3.1 standard for more information. **See also:** - MPI\_Mprobe <#mpi-mprobe> - MPI\_Probe <#mpi-probe> - MPI\_Iprobe <#mpi-iprobe> - MPI\_Mrecv <#mpi-mrecv> - MPI\_Imrecv <#mpi-imrecv> - MPI\_Cancel <#mpi-cancel> # [Copyright](#Copyright) 2003-2026, The Open MPI Community September 16, 2026 --- Document: MPI_Improbe(3) from openmpi-cuda-12.6 5.0.11-r1 (Chainguard OS) Source: https://github.com/open-mpi/ompi