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From: jim@interet.UUCP (User)
Newsgroups: comp.lang.fortran
Subject: Re: f2c is almost great
Summary: here are benchmarks for f2c
Keywords: f2c fortran benchmarks
Message-ID: <4@interet.UUCP>
Date: 24 Aug 90 19:25:29 GMT
References: <3@interet.UUCP>
Organization: Interet, Maplewood, NJ
Lines: 43


Here are some benchmarks comparing the f2c compiler with two Fortran  com-
pilers.    The  benchmark program is 3,616 lines of Fortran.  It is a sim-
plex linear optimization engine which reads in  the  problem  coefficients
from disk, solves the problem, and writes about 30 lines of results to the
terminal.  This is a real-world program that we actually use.  It is writ-
ten  in  elementary Fortran, it uses only double precision floating point,
no transcendental functions, and uses  sparse  matrix  techniques.   Times
given  are  the  sum  of  "user" and "system" time as reported by the Unix
"time" command.  The problem is CPU intensive, and  "system"  time  is  at
most a few percent of "user" time.   The program was tested on a small and
a large problem.

For each computer the same Fortran source was compiled using  the  maximum
optimization level.  Then the Fortran source was converted to C using f2c.
Then the C source was compiled using maximum  optimization.   The  answers
agreed  to  the  ten decimal places printed, but Fortran writes "D+02" and
f2c writes "E+02".

The first tests were run on a Pyramid 9810 under  OS  5.0c  using  Pyramid
Fortran  4.4.0  dated 4-28-89, and the Pyramid C compiler Ver 4.7 dated 4-
12-89.  Results were:

Fortran small problem:  596 iterations,  20.2 seconds, relative 1.00
f2c     small problem:  592 iterations,  26.1 seconds, relative 1.29
Fortran large problem: 1860 iterations, 131.4 seconds, relative 1.00
f2c     large problem: 2095 iterations, 199.6 seconds, relative 1.52 (1.35)

Then the same tests were run on a Sun 3/60 under OS 4.0.3 and Fortran 1.3.
Results were:

Fortran small problem:  575 iterations,  44.9 seconds, relative 1.00
f2c     small problem:  625 iterations,  54.5 seconds, relative 1.21
Fortran large problem: 2028 iterations, 330.5 seconds, relative 1.00
f2c     large problem: 2024 iterations, 356.8 seconds, relative 1.08

Interpretation is complicated by the fact that a different number of  sim-
plex  iterations  were performed by different cases, even though the prob-
lems were identical.  For these benchmarks, f2c is always slower by 8%  to
either  52%  or 35% (depending on whether total time or time per iteration
is used).

Jim      the grizzled Fortran hacker     uunet!interet!jim