From: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
To: "Cristian Rodríguez" <cristian@rodriguez.im>,
"Adhemerval Zanella Netto" <adhemerval.zanella@linaro.org>
Cc: GNU C Library <libc-alpha@sourceware.org>
Subject: Re: [PATCH 2/2] Add single-threaded fast path to rand()
Date: Wed, 20 Mar 2024 14:28:43 +0000 [thread overview]
Message-ID: <PAWPR08MB8982A94E3509AA7515A087C083332@PAWPR08MB8982.eurprd08.prod.outlook.com> (raw)
In-Reply-To: <CAPBLoAdYdzN6ML7FZ=9TUn2_-2z91MOETfsx3ZB5Jxpj6U3j7Q@mail.gmail.com>
Hi Cristian,
> Yeah, it should be no surprise this interfaces are bad,
> I thought this was common knowledge.
It's bad but we also made it thread-safe via locks rather than add its state to TLS.
> we need something like https://github.com/C2SP/C2SP/blob/main/chacha8rand.md
> which prety much outperforms even non-CS algorithms in at least 64 bit x86.
> but the question of the state remains.global? TLS? how to discard it
> in all the appropriate occasions?
I believe the current implementation is already way overkill. All you need is a simple
LFSR random generator with 64 bits of state and a decently large cycle. It's not
meant to be a serious random number generator - it's invariably used to generate
randomized inputs for testing and benchmarking. That's all. The complaints are
due to it being too slow due to all the locking.
Cheers,
Wilco
next prev parent reply other threads:[~2024-03-20 14:29 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-18 15:20 Wilco Dijkstra
2024-03-18 19:24 ` Cristian Rodríguez
2024-03-19 15:44 ` Wilco Dijkstra
2024-03-20 12:31 ` Adhemerval Zanella Netto
2024-03-20 14:18 ` Cristian Rodríguez
2024-03-20 14:27 ` Adhemerval Zanella Netto
2024-03-21 7:39 ` Florian Weimer
2024-03-21 13:33 ` Cristian Rodríguez
2024-03-21 14:35 ` Mathieu Desnoyers
2024-03-21 15:07 ` Szabolcs Nagy
2024-03-21 15:18 ` Wilco Dijkstra
2024-03-21 15:53 ` Adhemerval Zanella Netto
2024-03-22 14:27 ` Zack Weinberg
2024-03-22 14:46 ` Adhemerval Zanella Netto
2024-03-22 15:30 ` Zack Weinberg
2024-03-22 18:05 ` Adhemerval Zanella Netto
2024-03-22 19:47 ` Mathieu Desnoyers
2024-03-22 22:54 ` Cristian Rodríguez
2024-03-23 14:01 ` Zack Weinberg
2024-03-23 15:23 ` Mathieu Desnoyers
2024-03-25 14:09 ` Mathieu Desnoyers
2024-03-25 17:52 ` Adhemerval Zanella Netto
2024-03-24 0:59 ` Cristian Rodríguez
2024-03-25 6:44 ` Florian Weimer
2024-03-20 14:28 ` Wilco Dijkstra [this message]
2024-03-20 14:40 ` Xi Ruoyao
-- strict thread matches above, loose matches on Subject: below --
2023-11-28 17:37 Wilco Dijkstra
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