examples/smpi/NAS/SP/make_set.f

   1
   2 c---------------------------------------------------------------------
   3 c---------------------------------------------------------------------
   4
   5        subroutine make_set
   6
   7 c---------------------------------------------------------------------
   8 c---------------------------------------------------------------------
   9
  10 c---------------------------------------------------------------------
  11 c This function allocates space for a set of cells and fills the set
  12 c such that communication between cells on different nodes is only
  13 c nearest neighbor
  14 c---------------------------------------------------------------------
  15
  16        include 'header.h'
  17        include 'mpinpb.h'
  18
  19        integer p, i, j, c, dir, size, excess, ierr,ierrcode
  20
  21 c---------------------------------------------------------------------
  22 c     compute square root; add small number to allow for roundoff
  23 c     (note: this is computed in setup_mpi.f also, but prefer to do
  24 c     it twice because of some include file problems).
  25 c---------------------------------------------------------------------
  26       ncells = dint(dsqrt(dble(no_nodes) + 0.00001d0))
  27
  28 c---------------------------------------------------------------------
  29 c      this makes coding easier
  30 c---------------------------------------------------------------------
  31        p = ncells
  32
  33 c---------------------------------------------------------------------
  34 c      determine the location of the cell at the bottom of the 3D
  35 c      array of cells
  36 c---------------------------------------------------------------------
  37        cell_coord(1,1) = mod(node,p)
  38        cell_coord(2,1) = node/p
  39        cell_coord(3,1) = 0
  40
  41 c---------------------------------------------------------------------
  42 c      set the cell_coords for cells in the rest of the z-layers;
  43 c      this comes down to a simple linear numbering in the z-direct-
  44 c      ion, and to the doubly-cyclic numbering in the other dirs
  45 c---------------------------------------------------------------------
  46        do    c=2, p
  47           cell_coord(1,c) = mod(cell_coord(1,c-1)+1,p)
  48           cell_coord(2,c) = mod(cell_coord(2,c-1)-1+p,p)
  49           cell_coord(3,c) = c-1
  50        end do
  51
  52 c---------------------------------------------------------------------
  53 c      offset all the coordinates by 1 to adjust for Fortran arrays
  54 c---------------------------------------------------------------------
  55        do    dir = 1, 3
  56           do    c = 1, p
  57              cell_coord(dir,c) = cell_coord(dir,c) + 1
  58           end do
  59        end do
  60
  61 c---------------------------------------------------------------------
  62 c      slice(dir,n) contains the sequence number of the cell that is in
  63 c      coordinate plane n in the dir direction
  64 c---------------------------------------------------------------------
  65        do   dir = 1, 3
  66           do   c = 1, p
  67              slice(dir,cell_coord(dir,c)) = c
  68           end do
  69        end do
  70
  71
  72 c---------------------------------------------------------------------
  73 c      fill the predecessor and successor entries, using the indices
  74 c      of the bottom cells (they are the same at each level of k
  75 c      anyway) acting as if full periodicity pertains; note that p is
  76 c      added to those arguments to the mod functions that might
  77 c      otherwise return wrong values when using the modulo function
  78 c---------------------------------------------------------------------
  79        i = cell_coord(1,1)-1
  80        j = cell_coord(2,1)-1
  81
  82        predecessor(1) = mod(i-1+p,p) + p*j
  83        predecessor(2) = i + p*mod(j-1+p,p)
  84        predecessor(3) = mod(i+1,p) + p*mod(j-1+p,p)
  85        successor(1)   = mod(i+1,p) + p*j
  86        successor(2)   = i + p*mod(j+1,p)
  87        successor(3)   = mod(i-1+p,p) + p*mod(j+1,p)
  88
  89 c---------------------------------------------------------------------
  90 c now compute the sizes of the cells
  91 c---------------------------------------------------------------------
  92        do    dir= 1, 3
  93 c---------------------------------------------------------------------
  94 c         set cell_coord range for each direction
  95 c---------------------------------------------------------------------
  96           size   = grid_points(dir)/p
  97           excess = mod(grid_points(dir),p)
  98           do    c=1, ncells
  99              if (cell_coord(dir,c) .le. excess) then
 100                 cell_size(dir,c) = size+1
 101                 cell_low(dir,c) = (cell_coord(dir,c)-1)*(size+1)
 102                 cell_high(dir,c) = cell_low(dir,c)+size
 103              else
 104                 cell_size(dir,c) = size
 105                 cell_low(dir,c)  = excess*(size+1)+
 106      >                   (cell_coord(dir,c)-excess-1)*size
 107                 cell_high(dir,c) = cell_low(dir,c)+size-1
 108              endif
 109              if (cell_size(dir, c) .le. 2) then
 110                 write(*,50)
 111  50             format(' Error: Cell size too small. Min size is 3')
 112                 call MPI_Abort(mpi_comm_world,ierrcode,ierr)
 113                 stop
 114              endif
 115           end do
 116        end do
 117
 118        return
 119        end
 120