Communication Examples

We further illustrate the use of Fortran M communication statements with the program ring2.fm. This program implements a ``ring pipeline'', in which NP processes are connected via a unidirectional ring. After NP-1 send-receive-compute cycles, each process has accumulated the value in the variable sum.

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      program ring2
      parameter (np=4)
      inport  (integer) ins(np)
      outport (integer) outs(np)
      do i = 1, np
         channel(in=ins(i), out=outs(mod(i,np)+1))
      enddo
      processdo i = 1, np
         processcall ringnode(i, np, ins(i), outs(i))
      endprocessdo
      end
      
      process ringnode(me, np, in, out)
      intent (in) me, np, in, out
      integer me, np
      inport  (integer) in
      outport (integer) out
      buff = me
      sum = buff
      do i = 1, np-1
         send(out) buff
         receive(in) buff
         sum = sum + buff
      enddo
      endchannel(out)
      receive(in) buff
      print *, 'node ', me, ' has sum = ', sum
      end