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Full Discussion: Making FORTRAN code more efficient
Top Forums Programming Making FORTRAN code more efficient Post 302443979 by drl on Tuesday 10th of August 2010 02:51:12 PM
Old 08-10-2010
Hi.

Here is a contrived code in Fortran-77 style (change the do-enddo to do ... statement-number, if you wish):
Code:
	program main
	parameter ( n = 10 000 000 )
	dimension t(n)
	do i = 1, n
	t(i) = i
	enddo
	call a ( t, int( .10*n ), sum )
	call b ( t, int( .25*n ), sum )
	call c ( t, n, sum )
	end
	subroutine a ( t, n, sum )
	write(*,*) " Entered: a"
	call a1 ( t, n, sum )
	return
	end
	subroutine a1 ( t, n, sum ) 
	dimension t(n)
	write(*,*) " Entered: a1"
	sum = 0
	do i=1,n
	sum = sum + t(i)
	enddo
	return
	end
	subroutine b ( t, n, sum )
	dimension t(n)
	write(*,*) " Entered: b"
	sum = 0
	do i=1,n
	sum = sum + t(i)
	enddo
	call b1
	return
	end
	subroutine b1
	write(*,*) " Entered: b1"
	call b2
	return
	end
	subroutine b2
	write(*,*) " Entered: b2"
	return
	end
	subroutine c ( t, n, sum )
	dimension t(n)
	write(*,*) " Entered: c"
	sum = 0
	do i=1,n
	sum = sum + t(i)
	enddo
	return
	end

We compile with GNU Fortran, and state that we wish to include profiling code:
Code:
#!/usr/bin/env bash

# @(#) s1	Demonstrate obtaining a Fortran execution profile.

pe() { for i;do printf "%s" "$i";done; printf "\n"; }
pl() { pe;pe "-----" ;pe "$*"; }
pe
# (Local utility version)
version gfortran gprof

FILE=one.f
rm -f a.out gmon.out

gfortran -pg $FILE
./a.out

gprof --brief

exit 0

Producing (excerpt):
Code:
gfortran GNU Fortran (Debian 4.3.2-1.1) 4.3.2
GNU gprof (GNU Binutils for Debian) 2.18.0.20080103
  Entered: a
  Entered: a1
  Entered: b
  Entered: b1
  Entered: b2
  Entered: c

...

  %   cumulative   self              self     total           
 time   seconds   seconds    calls  ms/call  ms/call  name    
 45.63      0.10     0.10        1   100.38   100.38  c_
 41.06      0.19     0.09        1    90.34   220.83  MAIN__
  9.13      0.21     0.02        1    20.08    20.08  b_
  4.56      0.22     0.01        1    10.04    10.04  a1_
  0.00      0.22     0.00        1     0.00    10.04  a_
  0.00      0.22     0.00        1     0.00     0.00  b1_
  0.00      0.22     0.00        1     0.00     0.00  b2_

Which would suggest that c and MAIN be looked at.

See man pages for details. Good luck ... cheers, drl
 

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LEARN ABOUT SUNOS

sum

sum(1B) 					     SunOS/BSD Compatibility Package Commands						   sum(1B)

NAME

       sum - calculate a checksum for a file

SYNOPSIS

       /usr/ucb/sum file...

DESCRIPTION

       sum  calculates	and  displays a 16-bit checksum for the named file and displays the size of the file in kilobytes. It is typically used to
       look for bad spots, or to validate a file communicated over some transmission line. The checksum is calculated by an  algorithm	which  may
       yield different results on machines with 16-bit ints and machines with 32-bit ints, so it cannot always be used to validate that a file has
       been transferred between machines with different-sized ints.

USAGE

       See largefile(5) for the description of the behavior of sum when encountering files greater than or equal to 2 Gbyte ( 2**31 bytes).

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWscpu			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       sum(1), wc(1), attributes(5), largefile(5)

DIAGNOSTICS

       Read error is indistinguishable from EOF on most devices; check the block count.

NOTES

       sum and /usr/bin/sum (see sum(1)) return different checksums.

       This utility is obsolete.

SunOS 5.10							    8 Nov 1995								   sum(1B)
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