From: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
To: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>,
"H.J. Lu" <hjl.tools@gmail.com>
Cc: "libc-alpha@sourceware.org" <libc-alpha@sourceware.org>,
kirill <kirill.okhotnikov@gmail.com>
Subject: Re: [PATCH v2 3/5] math: Improve fmod
Date: Thu, 16 Mar 2023 16:13:47 +0000 [thread overview]
Message-ID: <PAWPR08MB8982CC4CAA371CB30CF8AE7483BC9@PAWPR08MB8982.eurprd08.prod.outlook.com> (raw)
In-Reply-To: <b17659bf-27fd-1cb6-a608-f5e381948917@linaro.org>
Hi,
It's these cases where x87 is still faster than the generic version:
> E5-2640 | close-exponents | 39.298 | 22.2742
>
> i7-4510U | close-exponents | 29.463 | 22.8572
Are these mostly x < y or cases where the exponent difference is just over 11 and
thus we do not use the fast path?
> I am also checking a algorithm change to use simple loop for the normal inputs,
> where integer modulo operation is used instead of inverse multiplication.
Adding another fast path for a wider range of exponent difference could be faster
than the generic modulo loop. This could do 2 modulo steps and maybe handle
tail zeroes (which I think is what HJ's testcase will benefit from).
For really large exponent differences, the generic modulo code could process 30
or 60 bits per iteration instead of just 11. It's more complex (so would be a separate
patch) but it should help CPUs with relatively high latency multipliers.
Cheers,
Wilco
next prev parent reply other threads:[~2023-03-16 16:14 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-15 20:59 [PATCH v2 0/5] Improve fmod and fmodf Adhemerval Zanella
2023-03-15 20:59 ` [PATCH v2 1/5] benchtests: Add fmod benchmark Adhemerval Zanella
2023-03-15 20:59 ` [PATCH v2 2/5] benchtests: Add fmodf benchmark Adhemerval Zanella
2023-03-15 20:59 ` [PATCH v2 3/5] math: Improve fmod Adhemerval Zanella
2023-03-16 0:58 ` H.J. Lu
2023-03-16 14:28 ` Adhemerval Zanella Netto
2023-03-16 16:13 ` Wilco Dijkstra [this message]
2023-03-16 20:39 ` Adhemerval Zanella Netto
2023-03-17 14:55 ` Wilco Dijkstra
2023-03-17 16:07 ` H.J. Lu
2023-03-17 18:22 ` Wilco Dijkstra
2023-03-15 20:59 ` [PATCH v2 4/5] math: Improve fmodf Adhemerval Zanella
2023-03-16 18:11 ` Wilco Dijkstra
2023-03-16 18:38 ` Adhemerval Zanella Netto
2023-03-16 19:15 ` Wilco Dijkstra
2023-03-16 19:45 ` Adhemerval Zanella Netto
2023-03-15 20:59 ` [PATCH v2 5/5] math: Remove the error handling wrapper from fmod and fmodf Adhemerval Zanella
2023-03-16 17:21 ` Wilco Dijkstra
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