Using Persistent Communication in Fortran MPI - fortran

Question

I am using persistent communication in my CFD code. I have the communications setup in another subroutine and in the main subroutine, where I have the do loop, I use the MPI_STARTALL(), MPI_WAITALL().
In order to make it shorter, I am showing hte first part of the setup. The rest of the arrays are exactly the same.
My setup subrotuine looks like:
Subroutine MPI_Subroutine
use Variables
use mpi
implicit none
!Starting up MPI
call MPI_INIT(ierr)
call MPI_COMM_SIZE(MPI_COMM_WORLD,npes,ierr)
call MPI_COMM_RANK(MPI_COMM_WORLD,MyRank,ierr)
!Compute the size of local block (1D Decomposition)
Jmax = JmaxGlobal
Imax = ImaxGlobal/npes
if (MyRank.lt.(ImaxGlobal - npes*Imax)) then
Imax = Imax + 1
end if
if (MyRank.ne.0.and.MyRank.ne.(npes-1)) then
Imax = Imax + 2
Else
Imax = Imax + 1
endif
! Computing neighboars
if (MyRank.eq.0) then
Left = MPI_PROC_NULL
else
Left = MyRank - 1
end if
if (MyRank.eq.(npes -1)) then
Right = MPI_PROC_NULL
else
Right = MyRank + 1
end if
! Initializing the Arrays in each processor, according to the number of local nodes
Call InitializeArrays
!Creating the channel of communication for this computation,
!Sending and receiving the u_old (Ghost cells)
Call MPI_SEND_INIT(u_old(2,:),Jmax,MPI_DOUBLE_PRECISION,Left,tag,MPI_COMM_WORLD,req(1),ierr)
Call MPI_RECV_INIT(u_old(Imax,:),jmax,MPI_DOUBLE_PRECISION,Right,tag,MPI_COMM_WORLD,req(2),ierr)
Call MPI_SEND_INIT(u_old(Imax-1,:),Jmax,MPI_DOUBLE_PRECISION,Right,tag,MPI_COMM_WORLD,req(3),ierr)
Call MPI_RECV_INIT(u_old(1,:),jmax,MPI_DOUBLE_PRECISION,Left,tag,MPI_COMM_WORLD,req(4),ierr)
Since I am debugging my code I am just checking these arrays. When I check my ghost cells are full of zeroes. Then I guess that I messing with the instruction.
The main code, where I call the MPI_STARTALL, MPI_WAITALL looks like:
Program
use Variables
use mpi
implicit none
open(32, file = 'error.dat')
Call MPI_Subroutine
!kk=kk+1
DO kk=1, 2001
! A lot of calculation
! communicating the maximum error among the processes and delta t
call MPI_REDUCE(eps,epsGlobal,1,MPI_DOUBLE_PRECISION,MPI_MAX,0,MPI_COMM_WORLD,ierr)
call MPI_BCAST(epsGlobal,1,MPI_DOUBLE_PRECISION,0,MPI_COMM_WORLD,ierr)
call MPI_REDUCE(delta_t,delta_tGlobal,1,MPI_DOUBLE_PRECISION,MPI_MIN,0,MPI_COMM_WORLD,ierr)
if(MyRank.eq.0) delta_t = delta_tGlobal
call MPI_BCAST(delta_t,1,MPI_DOUBLE_PRECISION,0,MPI_COMM_WORLD,ierr)
if(MyRank.eq.0) then
write(*,*) kk,epsGlobal,(kk*delta_t)
write(32,*) kk,epsGlobal
endif
Call Swap
Call MPI_STARTALL(4,req,ierr) !
Call MPI_WAITALL(4,req,status,ierr)
enddo
The variables are set in another module. the MPI related variables looks like:
! MPI variables
INTEGER :: npes, MyRank, ierr, Left, Right, tag
INTEGER :: status(MPI_STATUS_SIZE,4)
INTEGER,dimension(4) :: req
I appreciate your time and suggestion in this problem.