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Re: [PATCH] Add sinh(tanh(x)) and cosh(tanh(x)) rules
- From: Wilco Dijkstra <Wilco dot Dijkstra at arm dot com>
- To: Giuliano Augusto Faulin Belinassi <giuliano dot belinassi at usp dot br>, "segher at kernel dot crashing dot org" <segher at kernel dot crashing dot org>
- Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>, "giuliano dot belinassi at gmail dot com" <giuliano dot belinassi at gmail dot com>, nd <nd at arm dot com>, Jeff Law <law at redhat dot com>
- Date: Fri, 19 Oct 2018 14:32:36 +0000
- Subject: Re: [PATCH] Add sinh(tanh(x)) and cosh(tanh(x)) rules
- References: <DB5PR08MB103001D43201E2827778B49F83E30@DB5PR08MB1030.eurprd08.prod.outlook.com> <CAEFO=4CV1P23fmb_kAv8u=ubJ5PejVFC59gFGnbNm2TrO-P38Q@mail.gmail.com> <20181019134511.GA1712@gate.crashing.org>,<CAEFO=4ApmEcpd-7ou2-_mdvMdGT4qphYdVcuZwpwYD=QvrDOeQ@mail.gmail.com>
Hi,
>> Maybe I am crazy, or the labels here are wrong, but that looks like the
>> error is three times as *big* after the patch. I.e. it worsened instead
>> of improving.
This error is actually 1ULP, so just a rounding error. Can't expect any better than that!
> with input : = 9.99999880790710449218750000000000000000000000000000e-01
> cosh: before: = 2.04800000000000000000000000000000000000000000000000e+03
> cosh: after : = 2.04800024414062500000000000000000000000000000000000e+03
> cosh: mpfr : = 2.04800006103515897848424084406334262726138617589463e+03
> error before: = 6.10351589784842408440633426272613861758946325324235e-05
> error after : = 1.83105466021515759155936657372738613824105367467577e-04
It may be less confusing to print relative error or ULP error...
Wilco