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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/96197] Excess memory consumption, positive correlation with the size of a constexpr array
Date: Wed, 15 Jul 2020 06:29:43 +0000 [thread overview]
Message-ID: <bug-96197-4-XL3zITBrtu@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-96197-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96197
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
Last reconfirmed| |2020-07-15
Known to fail| |10.1.0, 11.0
Keywords| |memory-hog
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Does it help if you replace your simplistic O(n) algorithms with O(log n) ones?
That is,
constexpr const struct word_type &WORD_LOOKUP(WORD index, const struct
word_type *table_row =word_table) {
for (;;) {
if (table_row->index == index) return *table_row;
if (table_row->index == WORD::NONE) return word_lookup(WORD::NONE);
++table_row;
}
// return table_row->index == index ? *table_row : (table_row->index ==
WORD::NONE ? word_lookup(WORD::NONE) : WORD_LOOKUP(index, ++table_row));
}
replace the for (;;) loop with table_row[index] (OK, that's maybe too much
guessing into your data structure) or with a binary search over the table
which you keep sorted?
It's probably simply garbage that accumulates during constexpr evaluation.
-ftime-report shows
constant expression evaluation : 28.45 ( 92%) 1.57 ( 96%) 32.97 ( 92%)
5127882 kB (100%)
that is 5GB of GC memory from constexpr evaluation.
next prev parent reply other threads:[~2020-07-15 6:29 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-14 15:30 [Bug c++/96197] New: " hyena at hyena dot net.ee
2020-07-15 6:29 ` rguenth at gcc dot gnu.org [this message]
2020-07-15 8:47 ` [Bug c++/96197] " hyena at hyena dot net.ee
2020-07-15 9:10 ` rguenther at suse dot de
2020-07-15 9:42 ` hyena at hyena dot net.ee
2020-07-21 16:17 ` ppalka at gcc dot gnu.org
2020-07-21 19:49 ` tridacnid at gmail dot com
2020-07-31 2:29 ` cvs-commit at gcc dot gnu.org
2020-07-31 13:51 ` ppalka at gcc dot gnu.org
2021-01-09 3:52 ` cvs-commit at gcc dot gnu.org
2021-01-09 3:54 ` ppalka at gcc dot gnu.org
2021-01-09 3:58 ` ppalka at gcc dot gnu.org
2021-01-18 15:39 ` ppalka at gcc dot gnu.org
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