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Communication Code

 A(N,N), B(N,N)
 DISTRIBUTE (*,BLOCK) A, B
 do i = 2, N-1
   do j = i, N-1
     A(i, j) = A(i-1, j-1)
   enddo
 enddo

For the above code segment, the last two examples find the computation decomposition (see section Owner Computes Rule) and that communication is needed when Ps > Pr (see section Find Existence of Communication). In this example separate loop nests for the distributed loop as well as receive and send instructions are found.

#iter = [2 <= i <= N - 1
         i <= j <= N - 1]

#dists = [ blk*Ps <= bsy < blk*Ps + blk ]
#distr = [ blk*Pr <= bry < blk*Pr + blk ]

#lhs = [bsx = i
        bsy = j ]

#rhs = [brx = i
        bry = j - 1 ]

#loop = { iter, dists, lhs }
#loop = loop.order(N Ps i j bsx bsy)
#loop = loop.rename(N P i j bx by)
loop.code(2)

#comm = { iter, dists, distr, lhs, rhs
          [ Ps > Pr ] }

#comms = comm.order(N Ps i Pr j bsx bsy brx bry)
#comms = comms.rename(N P i Pr j bx by brx bry)
comms.code(2)

#commr = comm.order(N Pr i Ps j brx bry bsx bsy)
#commr = commr.rename(N P i Ps j bx by bsx bsy)
commr.code(2)
end

The printout of the example session:

csh> lic -c
Rapid Prototyping System for Code Generation
> < example5
#iter = [2 <= i <= N - 1
         i <= j <= N - 1]

#dists = [ blk*Ps <= bsy < blk*Ps + blk ]
#distr = [ blk*Pr <= bry < blk*Pr + blk ]

#lhs = [bsx = i
        bsy = j ]

#rhs = [brx = i
        bry = j - 1 ]

#loop = { iter, dists, lhs }
#loop = loop.order(N Ps i j bsx bsy)
#loop = loop.rename(N P i j bx by)
loop.code(2)

for(P = 2/blk; P <= (-1+N)/blk; P++)
   for(i = 2; i <= min(-1+N, -1+blk+blk*P); i++)
      for(j = max(blk*P, i); j <= min(-1+N, -1+blk+blk*P); j++) {
         bx = i;
         by = j;
      }

#comm = { iter, dists, distr, lhs, rhs
          [ Ps > Pr ] }

#comms = comm.order(N Ps i Pr j bsx bsy brx bry)
#comms = comms.rename(N P i Pr j bx by brx bry)
comms.code(2)

for(P = (1+blk)/blk; P <= (-1+N)/blk; P++)
   for(i = 2; i <= blk*P; i++) {
      Pr = -1+P;
      j = blk+blk*Pr;
      bx = i;
      by = j;
      brx = i;
      bry = -1+j;
   }

#commr = comm.order(N Pr i Ps j brx bry bsx bsy)
#commr = commr.rename(N P i Ps j bx by bsx bsy)
commr.code(2)

for(P = 1/blk; P <= (-1-blk+N)/blk; P++)
   for(i = 2; i <= blk+blk*P; i++) {
      Ps = 1+P;
      j = blk*Ps;
      bx = i;
      by = -1+blk*Ps;
      bsx = bx;
      bsy = blk*Ps;
   }

end
> quit
done(0)

csh>

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