루프에서 데이터를 보내고받는 방법

do 루프에서 데이터를 보내고받는 데 문제가 있습니다. 아래 코드를 확인하십시오.

  include 'mpif.h'
  parameter (NRA = 4)
  parameter (NCA = 4)
  parameter (MASTER = 0)
  parameter (FROM_MASTER = 1)
  parameter (FROM_WORKER = 2)

  integer   numtasks,taskid,numworkers,source,dest,mtype,
 &          cols,avecol,extra, offset,i,j,k,ierr,rc
  integer status(MPI_STATUS_SIZE)
  real*8    a(NRA,NCA)

  call MPI_INIT( ierr )
  call MPI_COMM_RANK( MPI_COMM_WORLD, taskid, ierr )
  call MPI_COMM_SIZE( MPI_COMM_WORLD, numtasks, ierr )
  numworkers = numtasks-1  
  print *, 'task ID= ',taskid
C *************************** master task *************************************
  if (taskid .eq. MASTER) then
  if (numworkers .NE. 2) then 
     print *, 'Please use 3 processors'
     print *,'Quitting...'
    call MPI_ABORT(MPI_COMM_WORLD,rc,ierr)
  endif
 C     Initialize A and B 
    do 30 i=1, NRA
      do 30 j=1, NCA
      a(i,j) = (i-1)+(j-1)
30     continue
C     Send matrix data to the worker tasks 
    avecol = NCA/numworkers
    extra = mod(NCA,numworkers)
    offset = 1
    mtype = FROM_MASTER
    do 50 dest=1, numworkers
      if (dest .le. extra) then
        cols = avecol + 1
      else
        cols = avecol
      endif
      write(*,*)'   sending',cols,' cols to task',dest
      call MPI_SEND(offset,1,MPI_INTEGER,dest,mtype, 
 &                   MPI_COMM_WORLD,ierr)
      call MPI_SEND(cols,1,MPI_INTEGER,dest,mtype, 
 &                   MPI_COMM_WORLD,ierr)
      call MPI_SEND(a(1,offset),cols*NRA,MPI_DOUBLE_PRECISION,
 &                   dest,mtype,MPI_COMM_WORLD,ierr )
      offset = offset + cols
50     continue
C     Receive results from worker tasks
    mtype = FROM_WORKER
    do 60 i=1, numworkers
      source = i
      call MPI_RECV(offset,1,MPI_INTEGER,source,
 &                   mtype,MPI_COMM_WORLD,status,ierr )
      call MPI_RECV(cols,1,MPI_INTEGER,source,
 &                   mtype,MPI_COMM_WORLD,status,ierr )
      call MPI_RECV(a(1,offset),cols*NRA,MPI_DOUBLE_PRECISION, 
 &                   source,mtype,MPI_COMM_WORLD,status,ierr)
60     continue
C     Print results 
    do 90 i=1, NRA
      do 80 j = 1, NCA
        write(*,70)a(i,j)
70        format(2x,f8.2,$)
80      continue
      print *, ' '
90    continue
  endif
C *************************** worker task *************************************
  if (taskid > MASTER) then
C     Receive matrix data from master task
    mtype = FROM_MASTER
    call MPI_RECV(offset,1,MPI_INTEGER,MASTER,
 &                 mtype,MPI_COMM_WORLD,status,ierr)
    call MPI_RECV( cols,1,MPI_INTEGER,MASTER,
 &                 mtype,MPI_COMM_WORLD,status,ierr)
    call MPI_RECV(a(1,offset),cols*NCA,MPI_DOUBLE_PRECISION,MASTER,
 &                 mtype,MPI_COMM_WORLD,status,ierr)
 start0 = offset
 end0 = offset+cols-1
 C     Do matrix multiply
    do t=1,5
      do i=1, NRA
        do j=start0,end0
          a(i,j) = a(i,j)*t
        enddo
      enddo
 C     Send results back to master task
    mtype = FROM_WORKER
    call MPI_SEND(offset,1,MPI_INTEGER,MASTER,mtype, 
 &                 MPI_COMM_WORLD,ierr)
    call MPI_SEND(cols,1,MPI_INTEGER,MASTER,mtype, 
 &                 MPI_COMM_WORLD,ierr)
    call MPI_SEND(a(1,offset),cols*NCA,MPI_DOUBLE_PRECISION,MASTER,
 &                  mtype,MPI_COMM_WORLD,ierr)
 enddo
  endif
  call MPI_FINALIZE(ierr)
  end

ado 루프 내부의 화면에 매번 matrix를 인쇄하고 싶습니다 . 코드를 실행하면 한 번만 인쇄됩니다. 즉, do 루프 ( t= 1) 의 처음으로 인쇄됩니다 . 이 코드를 수정하여 계산 a된 후 매번 화면에 매트릭스를 인쇄 할 수 있도록하는 방법입니다.