From: Joseph Myers <joseph@codesourcery.com>
To: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
Cc: Adhemerval Zanella <adhemerval.zanella@linaro.org>,
'GNU C Library' <libc-alpha@sourceware.org>
Subject: Re: [PATCH v2 4/9] math: Use an improved algorithm for hypot (dbl-64)
Date: Thu, 28 Oct 2021 17:19:51 +0000 [thread overview]
Message-ID: <alpine.DEB.2.22.394.2110281718590.1736839@digraph.polyomino.org.uk> (raw)
In-Reply-To: <VE1PR08MB5599F681F87C0DE5490B6B6483869@VE1PR08MB5599.eurprd08.prod.outlook.com>
On Thu, 28 Oct 2021, Wilco Dijkstra via Libc-alpha wrote:
> + h = math_narrow_eval (h * scale);
> + math_check_force_underflow_nonneg (h);
> + return h;
>
> I don't think you need math_check_force_underflow_nonneg at all given
> h * scale should already set the underflow flag correctly. Removing this
> gives performance within ~2% of the original.
Scaling down doesn't set the underflow flag if the scaling down was exact
(even though the actual hypot operation is inexact and so should raise
underflow).
--
Joseph S. Myers
joseph@codesourcery.com
next prev parent reply other threads:[~2021-10-28 17:19 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-28 15:19 Wilco Dijkstra
2021-10-28 17:19 ` Joseph Myers [this message]
2021-10-29 12:38 ` Wilco Dijkstra
2021-10-29 16:20 ` Joseph Myers
-- strict thread matches above, loose matches on Subject: below --
2021-10-25 11:57 [PATCH v2 0/9] Improve hypot() Adhemerval Zanella
2021-10-25 11:57 ` [PATCH v2 4/9] math: Use an improved algorithm for hypot (dbl-64) Adhemerval Zanella
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