Dear all,

I am a beginner of MPI, right now I try to use MPI_GATHERV in my code, the test code just gather the value of array A to store them in array B, but I found an error listed as follows,

'Fatal error in MPI_Gatherv: Invalid count, error stack:

PMPI_Gatherv<398>: MPI_Gatherv failed <sbuf=004d96c0, scount=64,MPI_REAL, rbuf=0049AC0, rcnts=003DCB8, displs=003D4C68, MPI_REAL, root=0, MPI_COMM_WORLD> failed

PMPI_Gatherv<317>: Negative count, value is -842150451’

Here I post my program with the email, I wonder anyone can help me to fix it or not? I guess my error is from the sending or receiving buffer and the displacement of the value stored, I tried to changed ‘B,jlen,idisp’ to ’ B(1,1), jlen(myid),idisp(myid)’ or other things, but I still cannot work it out.

I am looking forward some help from you.

Zhangping Wei

 

my code is,

      PROGRAM MAIN

      IMPLICIT NONE

      INCLUDE 'mpif.h'

      INTEGER I,J,IWORK,JWORK,I1,I2,J1,J2

      REAL A(16,16),B(16,16)

      INTEGER,ALLOCATABLE ::idisp(:),jlen(:)

      integer myid,numprocs,rc,ierr,istar,iend,jstar,jend

      integer status(MPI_STATUS_SIZE)

      CALL MPI_INIT(ierr)

      CALL MPI_COMM_RANK(MPI_COMM_WORLD,myid,ierr)

      CALL MPI_COMM_SIZE(MPI_COMM_WORLD,numprocs,ierr)

 !     PRINT *,'process ',myid, 'of',numprocs, 'is alive.'  

      allocate(idisp(0:numprocs-1),jlen(0:numprocs-1))     

      DO J=1,16

        DO I=1,16

            A(I,J)=I+J

            B(I,J)=0.0

        ENDDO

      ENDDO

          I1=1;I2=16;J1=1;J2=16

            JWORK=(J2-J1)/numprocs+1

            JSTAR=MIN(myid*JWORK+J1,J2+1)

            JEND=MIN(JSTAR+JWORK-1,J2)

            ISTAR=I1

            IEND=I2                       

      PRINT *,myid,istar,iend,jstar,jend

      jlen(myid)=16*(jend-jstar+1)

      idisp(myid)=16*(jstar-1)

      print *,myid,jlen(myid),idisp(myid)    

      CALL MPI_GATHERV(A(1,jstar),jlen(myid),MPI_REAL,

     *B,jlen,idisp,MPI_REAL,0,MPI_COMM_WORLD,IERR)

      IF(myid.EQ.0)THEN

        DO J=1,16

            DO I=1,16

                PRINT *,I,J,B(I,J)

            ENDDO

        ENDDO     

      ENDIF

      CALL MPI_Finalize(rc)                                        

      END PROGRAM