MPI_Neighbor_alltoallw_init(3) MPI MPI_Neighbor_alltoallw_init(3) NAME MPI_Neighbor_alltoallw_init - Create a persistent request for neigh- bor_alltoallw. SYNOPSIS int MPI_Neighbor_alltoallw_init(const void *sendbuf, const int sendcounts[], const MPI_Aint sdispls[], const MPI_Datatype sendtypes[], void *recvbuf, const int recvcounts[], const MPI_Aint rdispls[], const MPI_Datatype recvtypes[], MPI_Comm comm, MPI_Info info, MPI_Request *request) int MPI_Neighbor_alltoallw_init_c(const void *sendbuf, const MPI_Count sendcounts[], const MPI_Aint sdispls[], const MPI_Datatype sendtypes[], void *recvbuf, const MPI_Count recvcounts[], const MPI_Aint rdispls[], const MPI_Datatype recvtypes[], MPI_Comm comm, MPI_Info info, MPI_Request *request) INPUT PARAMETERS sendbuf - starting address of send buffer (choice) sendcounts - non-negative integer array (of length outdegree) specifying the number of elements to send to each neighbor (non-negative integer) sdispls - integer array (of length outdegree). Entry j specifies the dis- placement in bytes (relative to sendbuf) from which to take the out- going data destined for neighbor j (integer) sendtypes - array of datatypes (of length outdegree). Entry j specifies the type of data to send to neighbor j (handle) recvcounts - non-negative integer array (of length indegree) specifying the number of elements that are received from each neighbor (non-nega- tive integer) rdispls - integer array (of length indegree). Entry i specifies the dis- placement in bytes (relative to recvbuf) at which to place the in- coming data from neighbor i (integer) recvtypes - array of datatypes (of length indegree). Entry i specifies the type of data received from neighbor i (handle) comm - communicator with topology structure (handle) info - info argument (handle) OUTPUT PARAMETERS recvbuf - starting address of receive buffer (choice) request - communication request (handle) THREAD AND INTERRUPT SAFETY This routine is thread-safe. This means that this routine may be safely used by multiple threads without the need for any user-provided thread locks. However, the routine is not interrupt safe. Typically, this is due to the use of memory allocation routines such as malloc or other non-MPICH runtime routines that are themselves not interrupt-safe. NOTES FOR FORTRAN All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK ) have an additional argument ierr at the end of the argument list. ierr is an inte- ger and has the same meaning as the return value of the routine in C. In Fortran, MPI routines are subroutines, and are invoked with the call state- ment. All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in Fortran. ERRORS All MPI routines (except MPI_Wtime and MPI_Wtick ) return an error value; C routines as the value of the function and Fortran routines in the last ar- gument. Before the value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job. The error han- dler may be changed with MPI_Comm_set_errhandler (for communicators), MPI_File_set_errhandler (for files), and MPI_Win_set_errhandler (for RMA windows). The MPI-1 routine MPI_Errhandler_set may be used but its use is deprecated. The predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarantee that an MPI program can continue past an error; however, MPI implementations will attempt to continue whenever possible. MPI_SUCCESS - No error; MPI routine completed successfully. MPI_ERR_ARG - Invalid argument. Some argument is invalid and is not identified by a specific error class (e.g., MPI_ERR_RANK ). MPI_ERR_BUFFER - Invalid buffer pointer. Usually a null buffer where one is not valid. MPI_ERR_COMM - Invalid communicator. A common error is to use a null communica- tor in a call (not even allowed in MPI_Comm_rank ). MPI_ERR_COUNT - Invalid count argument. Count arguments must be non-negative; a count of zero is often valid. MPI_ERR_INFO - Invalid Info MPI_ERR_TYPE - Invalid datatype argument. Additionally, this error can occur if an uncommitted MPI_Datatype (see MPI_Type_commit ) is used in a com- munication call. MPI_ERR_OTHER - Other error; use MPI_Error_string to get more information about this error code. 4/10/2026 MPI_Neighbor_alltoallw_init(3)
NAME | SYNOPSIS | INPUT PARAMETERS | OUTPUT PARAMETERS | THREAD AND INTERRUPT SAFETY | NOTES FOR FORTRAN | ERRORS
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