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From: Andrew Haley <aph@redhat.com>
To: "Ondřej Bílka" <neleai@seznam.cz>
Cc: "Joseph S. Myers" <joseph@codesourcery.com>,
	       Siddhesh Poyarekar <siddhesh@redhat.com>,
	libc-alpha@sourceware.org,        libc-ports@sourceware.org
Subject: Re: [PATCH][BZ #14412] Define __sincos_finite as a fast version of sincos
Date: Mon, 29 Apr 2013 14:53:00 -0000	[thread overview]
Message-ID: <517E894C.8090602@redhat.com> (raw)
In-Reply-To: <20130429141553.GC24033@domone.kolej.mff.cuni.cz>

On 04/29/2013 03:15 PM, Ondřej Bílka wrote:
> On Mon, Apr 29, 2013 at 01:34:42PM +0000, Joseph S. Myers wrote:
>> On Mon, 29 Apr 2013, Siddhesh Poyarekar wrote:
>>
>>> This patch brings back the assembly implementation of sincos (with
>>> some changes) to give a fast alternative to the default sincos
>>> implementation.  This is defined as __sincos_finite and is used if the
>>> implementing program is compiled with the -ffinite-math-only gcc flag.
>>
>> The changes don't seem to include accurate range reduction.  Without that, 
>> I think this is inappropriate, as it will result in wildly inaccurate 
>> results for large but finite inputs.
>>
> These inputs contain zero significant digits. You cannot expect any
> accuracty from them.

You can't possibly know that.  If the caller asks for sin(2^80) you should
return a close approximation to sin(2^80), not garbage.

Andrew.


  reply	other threads:[~2013-04-29 14:53 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-04-29 10:26 Siddhesh Poyarekar
2013-04-29 13:31 ` Andreas Schwab
2013-04-29 13:34 ` Joseph S. Myers
2013-04-29 14:02   ` Siddhesh Poyarekar
2013-04-29 14:16   ` Ondřej Bílka
2013-04-29 14:53     ` Andrew Haley [this message]
2013-04-29 15:19       ` Rich Felker
2013-04-30  8:59 ` Ondřej Bílka
2013-04-30  9:03   ` Siddhesh Poyarekar

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