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

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

ENDIF

CALL MPI_Finalize(rc)

END PROGRAM