From: Jonathan Wakely <jwakely.gcc@gmail.com>
To: Eelis <eelis@eelis.net>
Cc: "libstdc++" <libstdc++@gcc.gnu.org>,
gcc-patches <gcc-patches@gcc.gnu.org>
Subject: Re: [patch, libstdc++] std::shuffle: Generate two swap positions at a time if possible
Date: Tue, 03 May 2016 12:39:00 -0000 [thread overview]
Message-ID: <CAH6eHdTnASg7A5USA_sTAHXPfUFmkrZvF27tZUJhj5ywwDVDag@mail.gmail.com> (raw)
In-Reply-To: <ng53cl$4iu$2@ger.gmane.org>
ENOPATCH
On 1 May 2016 at 15:21, Eelis <eelis@eelis.net> wrote:
> Sorry, forgot to include the libstdc++ list.
>
> On 2016-05-01 16:18, Eelis wrote:
>>
>> Hi,
>>
>> The attached patch optimizes std::shuffle for the very common case
>> where the generator range is large enough that a single invocation
>> can produce two swap positions.
>>
>> This reduces the runtime of the following testcase by 37% on my machine:
>>
>> int main()
>> {
>> std::mt19937 gen;
>>
>> std::vector<int> v;
>> v.reserve(10000);
>> for (int i = 0; i != 10000; ++i)
>> {
>> v.push_back(i);
>> std::shuffle(v.begin(), v.end(), gen);
>> }
>>
>> std::cout << v.front() << '\n';
>> }
>>
>> Thoughts?
>>
>> Thanks,
>>
>> Eelis
>>
>
>
next prev parent reply other threads:[~2016-05-03 12:39 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-01 14:18 Eelis
2016-05-01 14:30 ` Eelis
2016-05-03 12:39 ` Jonathan Wakely [this message]
2016-05-03 14:42 ` Eelis van der Weegen
2016-05-25 19:54 ` Eelis
2016-05-25 20:45 ` Eelis
2016-08-31 12:45 ` Jonathan Wakely
2016-09-01 15:14 ` Jonathan Wakely
2016-09-01 15:27 ` Marc Glisse
2016-09-01 15:35 ` Jonathan Wakely
2016-09-01 15:31 ` Eelis van der Weegen
2016-09-01 15:37 ` Jonathan Wakely
2016-09-02 18:20 ` Eelis van der Weegen
2016-09-02 18:53 ` Eelis
2016-09-02 19:27 ` Eelis
2016-10-14 19:42 ` Jonathan Wakely
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