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From: Jan C. =?iso-8859-1?Q?Vorbr=FCggen?= <jvorbrueg...@mediasec.de>
Newsgroups: comp.lang.fortran
Subject: Re: F90 performace problem on SGI (vs f77)
Date: Tue, 17 Sep 2002 14:07:08 +0200
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Attached you'll find a little test program. Compiling the two files seperately
/fast and linking them with CVF 6.6A, I get the following results:

Loop count:10
   6.960000      for array operation
   6.760000      for loop

Loop count:20
   13.62000      for array operation
   13.50900      for loop

Loop count:30
   20.46000      for array operation
   20.25900      for loop

Loop count:30
   20.40000      for array operation
   20.36900      for loop

So there's a ~2% difference between the two. If I leave out the call to
do_nothing, the run time is always 0.0, as expected 8-|.

	Jan

	program test

	implicit none

	real(8) q1(2100,2100), q2(2000,2000)
	integer start, stop, rate
	integer i, j, c, count

	write (*, "(A)", advance="no") "Loop count:"
	read (*, *) count

	call system_clock (count_rate = rate)

	call random (q2)

	call system_clock (count = start)

	do c = 1, count
	  q1(51:2050, 51:2050) = q2
	  call do_nothing (q1)
	enddo

	call system_clock (count = stop)

	write (*, *) FLOAT(stop-start)/FLOAT(rate), " for array operation"

	call system_clock (count = start)

	do c = 1, count
	  do j = 1,2000
  	    do i=1,2000
	      q1 (i+50, j+50) = q2 (i, j)   
	    enddo
	  enddo 
	  call do_nothing (q1)
	enddo

	call system_clock (count = stop)

	write (*, *) FLOAT(stop-start)/FLOAT(rate), " for loop"

	end program test
!
!	must be in seperate file and compiled seperately....
!
	subroutine do_nothing (x)
	real(8) x(*)

	return

	end