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Optimize: Test large equivalence classes for conflict first.

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This reduces the execution time of gperf on large inputs by ca. 10%.

* src/search.cc (cmp_equiv_classes): New function.
(compute_partition): Sort the equivalence classes according to
decreasing size.
This commit is contained in:
Bruno Haible
2025-04-19 19:57:12 +02:00
parent 9e29799ac3
commit 70899c856b
2 changed files with 30 additions and 0 deletions
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ChangeLog
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@@ -1,3 +1,11 @@
2025-04-19 Bruno Haible <bruno@clisp.org>
Optimize: Test large equivalence classes for conflict first.
This reduces the execution time of gperf on large inputs by ca. 10%.
* src/search.cc (cmp_equiv_classes): New function.
(compute_partition): Sort the equivalence classes according to
decreasing size.
2025-04-19 Bruno Haible <bruno@clisp.org>
Refactor: Use an array-list instead of a linked-list of equiv.-classes.

22
src/search.cc
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@@ -1011,6 +1011,19 @@ undetermined_hashcode (KeywordExt *key)
return key->_undetermined_chars_hashcode;
}
/* Compares the equivalence classes cls1, cls2 pointed to by ptr1 and ptr2
and returns
< 0 if cls1 is larger than cls2,
0 if cls1 and cls2 have the same size,
> 0 if cls1 is smaller than cls1. */
static int
cmp_equiv_classes (void const *ptr1, void const *ptr2)
{
EquivalenceClass const *cls1 = static_cast<EquivalenceClass const *>(ptr1);
EquivalenceClass const *cls2 = static_cast<EquivalenceClass const *>(ptr2);
return _GL_CMP (cls2->_keywords.size(), cls1->_keywords.size());
}
Partition *
Search::compute_partition (bool *undetermined) const
{
@@ -1067,6 +1080,15 @@ Search::compute_partition (bool *undetermined) const
}
}
/* Sort the equivalence classes according to decreasing size.
This results in a speedup of find_asso_values, because on average, a large
equivalence class has a higher probability for a collision than a smaller
equivalence class. (An equivalence class with just 1 keyword never has
a collision.) */
if (partition->_equclasses.size() > 1)
qsort (&partition->_equclasses.get_at(0), partition->_equclasses.size(),
sizeof (EquivalenceClass), cmp_equiv_classes);
return partition;
}