From: rixed@happyleptic.org
To: 10651@debbugs.gnu.org
Subject: bug#10651: compiling pattern matching for (or ...) takes forever
Date: Mon, 30 Jan 2012 11:10:36 +0100 [thread overview]
Message-ID: <20120130101036.GA20941@ccellier.rd.securactive.lan> (raw)
Not really a bug per se (although the manual states that "When Guile
hangs or takes forever to complete a task, it is a bug."), but the time
complexity behind the compilation of (or ...) patterns in (ice-9 match)
module is so high that anything more than 8 sub-patterns takes forever
for me. Here is a short demonstration of the problem:
% time guile -c "([@ (ice-9 match) match] '(a b) [(or ('a 'b) ('a 'b)) 'ab])"
0.06s user 0.00s system 102% cpu 0.054 total
% time guile -c "([@ (ice-9 match) match] '(a b) [(or ('a 'b) ('a 'b) ('a 'b)) 'ab])"
0.13s user 0.01s system 99% cpu 0.136 total
% time guile -c "([@ (ice-9 match) match] '(a b) [(or ('a 'b) ('a 'b) ('a 'b) ('a 'b)) 'ab])"
0.44s user 0.01s system 100% cpu 0.443 total
% time guile -c "([@ (ice-9 match) match] '(a b) [(or ('a 'b) ('a 'b) ('a 'b) ('a 'b) ('a 'b)) 'ab])"
1.78s user 0.01s system 100% cpu 1.792 total
% time guile -c "([@ (ice-9 match) match] '(a b) [(or ('a 'b) ('a 'b) ('a 'b) ('a 'b) ('a 'b) ('a 'b)) 'ab])"
7.28s user 0.02s system 100% cpu 7.308 total
% time guile -c "([@ (ice-9 match) match] '(a b) [(or ('a 'b) ('a 'b) ('a 'b) ('a 'b) ('a 'b) ('a 'b) ('a 'b)) 'ab])"
29.31s user 1.50s system 99% cpu 30.823 total
% time guile -c "([@ (ice-9 match) match] '(a b) [(or ('a 'b) ('a 'b) ('a 'b) ('a 'b) ('a 'b) ('a 'b) ('a 'b) ('a 'b)) 'ab])"
133.75s user 0.14s system 99% cpu 2:13.94 total
% time guile -c "([@ (ice-9 match) match] '(a b) [(or ('a 'b) ('a 'b) % ('a 'b) ('a 'b) ('a 'b) ('a 'b) ('a 'b) ('a 'b) ('a 'b) 'ab])"
?
It's easy to work around by splitting the or in smaller chunks but it
can take some time to understand why the compiler hangs. I believe such
time complexity behavior should be advertised in the manual.
next reply other threads:[~2012-01-30 10:10 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-30 10:10 rixed [this message]
2012-05-21 20:51 ` bug#10651: There should be a fix to this bug Stefan Israelsson Tampe
2012-06-08 10:45 ` Ludovic Courtès
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