ArrDescrInit Subroutine

      subroutine ArrDescrInit(ArrDes,comm,im_world,jm_world,lm_world,nx,ny,num_readers,num_writers,is,ie,js,je,rc)
         type(ArrDescr), intent(INOUT) :: ArrDes
         integer, intent(in) :: comm
         integer, intent(in) :: IM_World
         integer, intent(in) :: JM_World
         integer, intent(in) :: lm_world
         integer, intent(in) :: nx
         integer, intent(in) :: ny
         integer, intent(in) :: num_readers
         integer, intent(in) :: num_writers
         integer, intent(in) :: is
         integer, intent(in) :: ie
         integer, intent(in) :: js
         integer, intent(in) :: je
         integer, optional, intent(out) :: rc

         integer :: color,myid,npes,NX0,NY0,ny_by_readers,ny_by_writers,j
         integer :: readers_comm, writers_comm, ioscattercomm,iogathercomm, xcomm,ycomm
         integer, allocatable :: i1(:),in(:),j1(:),jn(:)
         integer, allocatable :: iminw(:),imaxw(:),jminw(:),jmaxw(:)
         integer :: imincnt,jmincnt,imaxcnt,jmaxcnt,i

         integer :: status

         call MPI_Comm_Rank(comm,myid,status)
         _VERIFY(status)
         call MPI_COMM_Size(comm,npes,status)
         _VERIFY(status)

         allocate(iminw(npes),imaxw(npes),jminw(npes),jmaxw(npes),stat=status)
         iminw=-1
         imaxw=-1
         jminw=-1
         jmaxw=-1
         iminw(myid+1)=is
         imaxw(myid+1)=ie
         jminw(myid+1)=js
         jmaxw(myid+1)=je
         call MPI_AllReduce(MPI_IN_PLACE,iminw,npes,MPI_INTEGER,MPI_MAX,comm,status)
         _VERIFY(STATUS)
         call MPI_AllReduce(MPI_IN_PLACE,imaxw,npes,MPI_INTEGER,MPI_MAX,comm,status)
         _VERIFY(STATUS)
         call MPI_AllReduce(MPI_IN_PLACE,jminw,npes,MPI_INTEGER,MPI_MAX,comm,status)
         _VERIFY(STATUS)
         call MPI_AllReduce(MPI_IN_PLACE,jmaxw,npes,MPI_INTEGER,MPI_MAX,comm,status)
         _VERIFY(STATUS)

         call MAPL_Sort(iminw)
         call MAPL_Sort(imaxw)
         call MAPL_Sort(jminw)
         call MAPL_Sort(jmaxw)

         allocate(i1(nx),in(nx),j1(ny),jn(ny))
         i1(1) = minval(iminw)
         in(1) = minval(imaxw)
         j1(1) = minval(jminw)
         jn(1) = minval(jmaxw)
         imincnt = 1
         imaxcnt = 1
         jmincnt = 1
         jmaxcnt = 1
         do i=1,npes
            if (iminw(i) > i1(imincnt)) then
               imincnt = imincnt + 1
               i1(imincnt) = iminw(i)
            end if
            if (imaxw(i) > in(imaxcnt)) then
               imaxcnt = imaxcnt + 1
               in(imaxcnt) = imaxw(i)
            end if
            if (jminw(i) > j1(jmincnt)) then
               jmincnt = jmincnt + 1
               j1(jmincnt) = jminw(i)
            end if
            if (jmaxw(i) > jn(jmaxcnt)) then
               jmaxcnt = jmaxcnt + 1
               jn(jmincnt) = jmaxw(i)
            end if
         enddo
         deallocate(iminw,imaxw,jminw,jmaxw)

         NX0 = mod(myid,nx) + 1
         NY0 = myid/nx + 1
         color = nx0
         call MPI_Comm_Split(comm,color,myid,ycomm,status)
         _VERIFY(status)
         color = ny0
         call MPI_Comm_Split(comm,color,myid,xcomm,status)
         _VERIFY(status)
         ! reader communicators
         if (num_readers > ny .or. mod(ny,num_readers) /= 0) then
            _RETURN(ESMF_FAILURE)
         end if
         ny_by_readers = ny/num_readers
         if (mod(myid,nx*ny/num_readers) ==0) then
            color = 0
         else
            color = MPI_UNDEFINED
         end if
         call MPI_COMM_SPLIT(comm,color,myid,readers_comm,status)
         _VERIFY(status)
         if (num_readers==ny) then
            IOscattercomm = xcomm
         else
            j = ny0 - mod(ny0-1,ny_by_readers)
            call MPI_Comm_Split(comm,j,myid,IOScattercomm,status)
            _VERIFY(status)
         endif
         ! writer communicators
         if (num_writers > ny .or. mod(ny,num_writers) /= 0) then
            _RETURN(ESMF_FAILURE)
         end if
         ny_by_writers = ny/num_writers
         if (mod(myid,nx*ny/num_writers) ==0) then
            color = 0
         else
            color = MPI_UNDEFINED
         end if
         call MPI_COMM_SPLIT(comm,color,myid,writers_comm,status)
         _VERIFY(status)
         if (num_writers==ny) then
            IOgathercomm = xcomm
         else
            j = ny0 - mod(ny0-1,ny_by_writers)
            call MPI_Comm_Split(comm,j,myid,IOgathercomm,status)
            _VERIFY(status)
         endif

         ArrDes%im_world=im_world
         ArrDes%jm_world=jm_world
         ArrDes%lm_world=lm_world

         ArrDes%readers_comm  = readers_comm
         ArrDes%ioscattercomm = ioscattercomm
         ArrDes%writers_comm  = writers_comm
         ArrDes%iogathercomm  = iogathercomm
         ArrDes%xcomm = xcomm
         ArrDes%ycomm = ycomm
         call mpi_comm_rank(arrdes%ycomm,arrdes%myrow,status)
         _VERIFY(status)

         allocate(arrdes%i1(size(i1)),_STAT)
         arrdes%i1=i1
         allocate(arrdes%in(size(in)),_STAT)
         arrdes%in=in
         allocate(arrdes%j1(size(j1)),_STAT)
         arrdes%j1=j1
         allocate(arrdes%jn(size(jn)),_STAT)
         arrdes%jn=jn

         ArrDes%NX0 = NY0
         ArrDes%NY0 = NX0

         ArrDes%offset = 0

         ArrDes%romio_cb_read  = "automatic"
         ArrDes%cb_buffer_size = "16777216"
         ArrDes%romio_cb_write = "enable"

         ArrDes%tile = .false.

         ArrDes%filename = ''

         _RETURN(ESMF_SUCCESS)

      end subroutine ArrDescrInit