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From: paul zimmermann <Paul.Zimmermann@inria.fr>
To: Szabolcs Nagy <nsz@port70.net>
Cc: Szabolcs.Nagy@arm.com, nd@arm.com, jens.gustedt@inria.fr,
	Vincent.Lefevre@ens-lyon.fr, musl@lists.openwall.com
Subject: Re: Re: musl mathematical functions
Date: Fri, 10 Jan 2020 19:35:08 +0100	[thread overview]
Message-ID: <mwv9pj2m8z.fsf@tomate.loria.fr> (raw)
In-Reply-To: <20200110173023.GS23985@port70.net> (message from Szabolcs Nagy on Fri, 10 Jan 2020 18:30:23 +0100)

       Dear Szabolcs,

> i think libm functions are extremely rarely used with
> non-nearest rounding mode so i think
> 
>   NR accuracy >> DR accuracy >> NR symmetry >> NR speed
>   >> DR symmetry >> DR speed
> 
> where NR is nearest rounding and DR is directed rounding.

yes this makes sense.

> and by accuracy i just mean correct behavirour with respect
> to exceptions and results (i.e. small ulp errors).

note that if directed rounding is used to implement interval
arithmetic, it is very important to have the return value on
the right side with respect to the exact value (at the cost
of a few ulps of accuracy).

Paul


  reply	other threads:[~2020-01-10 18:35 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <mwlfqit6tx.fsf@tomate.loria.fr>
2020-01-08 15:28 ` Szabolcs Nagy
2020-01-08 15:46   ` Rich Felker
2020-01-10 16:01   ` paul zimmermann
2020-01-10 17:30     ` Szabolcs Nagy
2020-01-10 18:35       ` paul zimmermann [this message]
2020-01-18 20:14         ` [musl] " Szabolcs Nagy

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