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From: paul zimmermann <Paul.Zimmermann@inria.fr>
Newsgroups: gmane.linux.lib.musl.general
Subject: Re: Re: musl mathematical functions
Date: Fri, 10 Jan 2020 19:35:08 +0100
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To: Szabolcs Nagy <nsz@port70.net>
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In-reply-to: <20200110173023.GS23985@port70.net> (message from Szabolcs Nagy
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       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