From: Jonathan Wakely <jwakely@redhat.com>
To: "François Dumont" <frs.dumont@gmail.com>
Cc: "libstdc++@gcc.gnu.org" <libstdc++@gcc.gnu.org>,
gcc-patches <gcc-patches@gcc.gnu.org>
Subject: Re: [PATCH] PR libstdc++/87135 Rehash only when necessary (LWG2156)
Date: Tue, 18 Sep 2018 08:46:00 -0000 [thread overview]
Message-ID: <20180918084159.GV23172@redhat.com> (raw)
In-Reply-To: <1ad7ad86-0f0c-e8b0-8f29-2b5303718988@gmail.com>
On 13/09/18 07:49 +0200, François Dumont wrote:
>All changes limited to hashtable_c++0x.cc file.
>
>_Prime_rehash_policy::_M_next_bkt now really does what its comment was
>declaring that is to say:
>Â // Return a prime no smaller than n.
>
>_Prime_rehash_policy::_M_need_rehash rehash only when _M_next_size is
>exceeded, not only when it is reach.
>
>Â Â Â PR libstdc++/87135
>Â Â Â * src/c++11/hashtable_c++0x.cc:
>Â Â Â (_Prime_rehash_policy::_M_next_bkt): Return a prime no smaller than
>Â Â Â requested size, but not necessarily greater.
>Â Â Â (_Prime_rehash_policy::_M_need_rehash): Rehash only if target size is
>Â Â Â strictly greater than next resize threshold.
>Â Â Â * testsuite/23_containers/unordered_map/modifiers/reserve.cc:
>Adapt test
>Â Â Â to validate that there is no rehash as long as number of insertion is
>Â Â Â lower or equal to the reserved number of elements.
>
>unordered_map tests successful, ok to commit once all other tests
>completed ?
>
>François
>diff --git a/libstdc++-v3/src/c++11/hashtable_c++0x.cc b/libstdc++-v3/src/c++11/hashtable_c++0x.cc
>index a776a8506fe..ec6031b3f5b 100644
>--- a/libstdc++-v3/src/c++11/hashtable_c++0x.cc
>+++ b/libstdc++-v3/src/c++11/hashtable_c++0x.cc
>@@ -46,10 +46,10 @@ namespace __detail
> {
> // Optimize lookups involving the first elements of __prime_list.
> // (useful to speed-up, eg, constructors)
>- static const unsigned char __fast_bkt[13]
>- = { 2, 2, 3, 5, 5, 7, 7, 11, 11, 11, 11, 13, 13 };
>+ static const unsigned char __fast_bkt[]
>+ = { 2, 2, 2, 3, 5, 5, 7, 7, 11, 11, 11, 11, 13, 13 };
>
>- if (__n <= 12)
>+ if (__n < sizeof(__fast_bkt) / sizeof(unsigned char))
sizeof(unsigned char) is defined to be 1, always.
I think this should be just sizeof(__fast_bkt), or if you're trying to
guard against the type of __fast_bkt changing, then use
sizeof(__fast_bkt) / sizeof(__fast_bkt[0]))
OK for trunk with either of those, instead of sizeof(unsigned char).
Thanks.
next prev parent reply other threads:[~2018-09-18 8:44 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-13 6:43 François Dumont
2018-09-18 8:46 ` Jonathan Wakely [this message]
2018-09-18 21:24 ` François Dumont
2018-09-19 9:16 ` Jonathan Wakely
2018-09-19 11:21 ` Jonathan Wakely
2018-09-19 16:24 ` François Dumont
2018-09-21 16:17 ` François Dumont
2018-09-21 17:13 ` Jonathan Wakely
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20180918084159.GV23172@redhat.com \
--to=jwakely@redhat.com \
--cc=frs.dumont@gmail.com \
--cc=gcc-patches@gcc.gnu.org \
--cc=libstdc++@gcc.gnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).