# 18.2.334. MPI_Startall

MPI_Startall — Starts a collection of requests.

## 18.2.334.1. SYNTAX

### 18.2.334.1.1. C Syntax

    #include <mpi.h>

    int MPI_Startall(int count, MPI_Request array_of_requests[])

### 18.2.334.1.2. Fortran Syntax

    USE MPI
    ! or the older form: INCLUDE 'mpif.h'
    MPI_STARTALL(COUNT, ARRAY_OF_REQUESTS, IERROR)
         INTEGER COUNT, ARRAY_OF_REQUESTS(*), IERROR

### 18.2.334.1.3. Fortran 2008 Syntax

    USE mpi_f08
    MPI_Startall(count, array_of_requests, ierror)
         INTEGER, INTENT(IN) :: count
         TYPE(MPI_Request), INTENT(INOUT) :: array_of_requests(count)
         INTEGER, OPTIONAL, INTENT(OUT) :: ierror

## 18.2.334.2. INPUT PARAMETER

- `count`: List length (integer).

## 18.2.334.3. INPUT/OUTPUT PARAMETER

- `array_of_requests`: Array of requests (array of handle).

## 18.2.334.4. OUTPUT PARAMETER

- `ierror`: Fortran only: Error status (integer).

## 18.2.334.5. DESCRIPTION

Starts all communications associated with requests in array_of_requests. A call to MPI_Startall(count, array_of_requests) has the same effect as calls to MPI_Start (&array_of_requests[i]), executed for i=0 ,…, count-1, in some arbitrary order.

A communication started with a call to MPI_Start or MPI_Startall is completed by a call to MPI_Wait, MPI_Test, or one of the derived functions MPI_Waitany, MPI_Testany, MPI_Waitall, MPI_Testall, MPI_Waitsome, MPI_Testsome (these are described in Section 3.7.5 of the MPI Standard, “Multiple Completions”). The request becomes inactive after successful completion by such a call. The request is not deallocated, and it can be activated anew by another MPI_Start or MPI_Startall call.

A persistent request is deallocated by a call to MPI_Request_free (see Section 3.7.3 of the MPI Standard, “Communication Completion”).

The call to MPI_Request_free can occur at any point in the program after the persistent request was created. However, the request will be deallocated only after it becomes inactive. Active receive requests should not be freed. Otherwise, it will not be possible to check that the receive has completed. It is preferable, in general, to free requests when they are inactive. If this rule is followed, then the persistent communication request functions will be invoked in a sequence of the form,
Create (Start Complete)* Free

where * indicates zero or more repetitions. If the same communication object is used in several concurrent threads, it is the user’s responsibility to coordinate calls so that the correct sequence is obeyed.

A send operation initiated with MPI_Start can be matched with any receive operation and, likewise, a receive operation initiated with MPI_Start can receive messages generated by any send operation.

## 18.2.334.6. 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.

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 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.

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.

See also

- MPI_Bsend_init

- MPI_Rsend_init

- MPI_Send_init

- MPI_Ssend_init

- MPI_Recv_init

- MPI_Start

- MPI_Request_free