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From: gsg0384@uxa.cso.uiuc.edu
Newsgroups: comp.lang.fortran
Subject: Re: How much illegal are these?
Message-ID: <116400002@uxa.cso.uiuc.edu>
Date: 22 Aug 89 02:31:00 GMT
Lines: 71
Nf-ID: #N:uxa.cso.uiuc.edu:116400002:000:1640
Nf-From: uxa.cso.uiuc.edu!gsg0384    Aug 21 21:31:00 1989



Ok, Ok.

The more detailed one that I wanted to ask is as follows:


      program main
      real a(200), b(10, 20), c(200)
      data b/200*1./, a/200*1./

      do 10 i = 1, 10
        b(i,1) = 0.
 10   continue

      do 20 j = 1, 10
        b(1,j) = 0.
 20   continue

      call sub(10, 10, a, b, c)

      print*, c

      stop
      end

c---------------
      subroutine sub(m, n, a, b, c)
      real a(m,n), b(m,n), c(m,n)

      do 20 i = 1, m
        do 10 j = 1, n
          c(i,j) = b(i,j)*a(i-1,j-1)
 10     continue
 20   continue

      return
      end
  

On Ardent1, there is a compiler switch -subcheck which gives warning at
run time.  But the result is what I intended, the c(.,.) = zero's for the
out-of-bounds.  Without the switch, the result is again what I intended.
  On Apollos (SR10.1), with the BSD f77 switch -C, the program terminates
with a message. 'Arithmetic exception: Subscript range'.  However,
without -C, the result was again what I inteded.

  OK.  SO they are illegal.  Then how about this modified sub?

c--------------
      subroutine sub(m, n, a, b, c)
      real a(m,n), b(m,n), c(m,n)

      do 20 i = 1, m
        do 10 j = 3, n
c                 ^ Notice!
          c(i,j) = b(i,j)*a(i-1,j-1)
 10     continue
 20   continue

      return
      end

The behavior on Apollo is the same.  But on Ardent, the compiler does not
catch anything wrong, even at the run time with -subcheck switch.
Ok, OK, They are still illegal.  Then how can I vectorize this without if's
and without introducing more do loops?

Thank you for kind replies in the past and for the new replies I get.

Hugh SONG