bad performance of g77(egcs) on Linux/Alpha

Toon Moene toon@moene.indiv.nluug.nl
Thu Apr 9 13:34:00 GMT 1998


Michal,

>  A concern was raised as the guy in question tried to use
>  g77 from egcs-1.0.1 on Linux/Alpha (LX running at 600
>  Mhz).  A performance was not spectacular (144 seconds).
>  After that he tried run the same code and on the same
>  Linux machine but compiled and linked statically with
>  OSF/1 compiler (version unknown).  He got 41 seconds for
>  a runtime.  This is a substantial discrepancy.

Agreed, normally the differences are not that large.

>  Is any reasonable explanation for these results beyond
>  that a library function log(), used by gammaln(), is
>  possibly awfull?

Well, the age-old way to determine this is to run the code on  
different architectures compiled with -pg and looking at the gprof  
output to see where it's spending its time.

>  I include below, for an ease of reference, a code which
>  compiles with g77, two version of gammaln() functions,
>  my Makefile, and three html documents, stolen from a
>  location mentioned above, which describe results achieved
>  with different hardware and compilers.

Unfortunately, you forgot to include the necessary input file, so I  
can't do this experiment on my own m68k-next-nextstep3 system.

Regards,
Toon.



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