[gambit-list] Running times: real vs. CPU

Taylor Venable taylor at metasyntax.net
Sat Apr 25 12:11:38 EDT 2009


Hi, I'm rather new to Gambit so I apologise if this is an incredibly
ignorant question.  I've been playing around with a few different
Scheme implementations and some Project Euler solutions, and I've been
quite surprised that many of them run much faster in MzScheme than
Gambit.  Looking into it further, it's only the *real* time that's
smaller, whereas the CPU time is nearly the same.  Here's an example
from source code at:

http://real.metasyntax.net:2357/cvs/cvsweb.cgi/Programs/Euler/Scheme/092.scm

For reference, I'm using Gambit 4.4.2 on OpenBSD 4.5 x86 configured
with --enable-single-host.

== GAMBIT 4.4.2
    with sum-of-squares in Scheme
    using `gsc -link` and `gcc -O2`

    real    1m34.795s
    user    0m46.520s
    sys     0m0.650s

== GAMBIT 4.4.2
    with sum-of-squares in C
    using `gsc -link` and `gcc -O2`

    real    0m46.421s
    user    0m19.380s
    sys     0m7.510s

(When using `gsc -flat` and loading into gsi I get pretty much exactly
the same times.)

== CHICKEN 4.0.0
    with sum-of-squares in Scheme
    using plain `csc`

    real    0m41.441s
    user    0m40.840s
    sys     0m0.600s

== MZSCHEME 4.1.4
    with sum-of-squares in Scheme
    using `mzscheme -f`

    real    0m25.530s
    user    0m25.330s
    sys     0m0.190s

Looking at the times, I'm confused about why Gambit's wall-clock run
time is nearly twice its on-CPU time.  The other two Scheme
implementations I tested only use about as much real time as total
on-CPU time.  I'm curious why Gambit uses so much more.

Thanks for any clarification,

-- 
Taylor Christopher Venable
http://real.metasyntax.net:2357/



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