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From: john@ghostwheel.unm.edu (John Prentice)
Newsgroups: comp.lang.fortran
Subject: Parallel Fortran question
Message-ID: <1990Dec11.055853.1248@ariel.unm.edu>
Date: 11 Dec 90 05:58:53 GMT
Sender: news@ariel.unm.edu (USENET News System)
Organization: University of New Mexico Math Dept., Albuquerque, NM
Lines: 53

I posted this earlier today, but it doesn't seem to have showed up.  If
you get two copies, my apologies.  John


I want to code the following for a shared memory parallel system:

      program yuppie
c
c        loop over subroutine
c
      integer n,nmax
      parameter (nmax=10)
      real hippie(nmax)
      do 10 n=1,nmax
          call yippie (hippie(n))
                  .
                  .
                  .
          call yippie (hippie(n))
                  .
                  .
                  .
   10 continue
      end
      subroutine yippie (hippie)
      real hippie
      logical first
      save first
      data first /.true./
c
      if (first) then
          .
        [initializations]
          .
          first=.false.
      endif
        .
        .
        .
      end

When yippie gets called the first time, it does some initializations.
Subsequent calls for the same loop iteration should not repeat the
initialization however (assume I am parallelizing the loop in the main
routine).  The way I wrote yippie works fine on a non-shared memory
machine, but not on a shared memory system.  This is because the save
statement causes yippie to always save first to the same memory location,
no matter which processor is being used.  On the Cray, you could use task
common to save the value of first, but there is no way to initialize task
common (that I know of).  Any suggestions?  Thanks.

John Prentice
john@unmfys.unm.edu