MPI_Gatherv

Gathers into specified locations from all processes in a group

Synopsis


#include "mpi.h"
int MPI_Gatherv ( sendbuf, sendcnt,  sendtype, 
                  recvbuf, recvcnts, displs, recvtype, 
                  root, comm )
void             *sendbuf;
int               sendcnt;
MPI_Datatype      sendtype;
void             *recvbuf;
int              *recvcnts;
int              *displs;
MPI_Datatype      recvtype;
int               root;
MPI_Comm          comm;

Input Parameters

sendbuf - starting address of send buffer (choice)
sendcount - number of elements in send buffer (integer)
sendtype - data type of send buffer elements (handle)
recvcounts - integer array (of length group size) containing the number of elements that are received from each process (significant only at root)
displs - integer array (of length group size). Entry i specifies the displacement relative to recvbuf at which to place the incoming data from process i (significant only at root)
recvtype - data type of recv buffer elements (significant only at root) (handle)
root - rank of receiving process (integer)
comm - communicator (handle)

Output Parameter

recvbuf - address of receive buffer (choice, significant only at root)

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 integer 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 statement.

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 argument. Before the value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job. The error handler may be changed with MPI_Errhandler_set; the predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarentee that an MPI program can continue past an error.

MPI_SUCCESS - No error; MPI routine completed successfully.
MPI_ERR_COMM - Invalid communicator. A common error is to use a null communicator in a call (not even allowed in MPI_Comm_rank).
MPI_ERR_TYPE - Invalid datatype argument. May be an uncommitted
MPI_Datatype (see MPI_Type_commit).
MPI_ERR_BUFFER - Invalid buffer pointer. Usually a null buffer where one is not valid.

Location:gatherv.c