new to gfortran & comparison with g77

[Philippe Depondt]

Hello,

  well I'm new to gfortran and have done some comparisons with g77 on a 
(Red-Hat)Linux system.

the results are the following :

free-form f77 code compiled with g77 (g77 -ffree-form -O chaine_pendul.f 
-o chaine_pendul)
executable file size (as given by ls -l) : 7733
execution time (time chaine_pendul) real 2.950s, user 2.9275s, sys 0.0007s

same code compiled with gfortran (gfortran -ffree-form -0 
chaine_pendul.f -o chaine_pendul)
executable file size : 665192
execution time : real 3.672s, user 3.204s, sys 0.468s

f90-style code compiled with gfortran (gfortran -O chain_pendul.f90 -o 
chaine_pendul)
executable file size : 663058
execution time : real 3.860s, user 3.286s, sys 0.574s

These results tend to make me believe I've got something wrong here... 
Any idea what ?
I've downloaded the i686 linux binaries from gfortran.org and started 
compiling and that's about it.


The program (both source codes attached) is a very simple solution for 
the equations of motion of a 1-D chain of 5000 coupled pendulums (I'm a 
physicist) with periodic boundary conditions using Verlet's algorithm. 
Decreasing the number of pendulums (i.e. the size of the arrays) will 
only increase the difference in execution time in favour of g77. My 
suspicion is that simply loading and handling the gigantic executables 
(approx 100 times larger than with g77!) requires quite a lot of 
resources, thus impeding performance...

Hoping I'm not just being a nuisance,


Ph.
-- 
Philippe Depondt                                    dep@ccr.jussieu.fr
# INSP                             Institut des Nano-Sciences de Paris
# Universite P. et M. Curie, Casier 86, 140 rue de Lourmel 75015 Paris
# Site Boucicaut : Bat. 2, 1er etage piece 4       Tel: 01 44 27 42 33
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