Re: [eigen] sse asin implementation |

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*To*: eigen@xxxxxxxxxxxxxxxxxxx*Subject*: Re: [eigen] sse asin implementation*From*: Gael Guennebaud <gael.guennebaud@xxxxxxxxx>*Date*: Thu, 2 Apr 2009 08:32:06 +0200*Dkim-signature*: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:in-reply-to:references :date:message-id:subject:from:to:content-type :content-transfer-encoding; bh=6bNIbrWpvSAfpho743ClEidy7LIgC054j3IVUbehxYc=; b=k2Rn7N3Umnc4Ikk3AqJ7DwCZ/bbs2cyWmoH4A0VevgQ6L0lg16ERAAasgMFhBRw+/z bEPPUC+94b/YiVG4965DgF0PWJJErxtYkOsfGC8rYXhodDoADHLlKhnesTKiq+TJXsQq n9gF+EdQFQOjRPD5aug7zjOgAnGU9NwvbNob8=*Domainkey-signature*: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type:content-transfer-encoding; b=dZb1blhnD4G0EMkwn6K7slmZS3DF1uS4/avUadq4HHig9xWfzNPRDBzPYJjK/t2nta /PJSy/z508bCevuckIHWiRFwTNtnKfNbcJbLNpg6A3e3aQl7lS4Xca2S3gUUZ8qSXKIw J3es/6uSCovduQhzPVhcW2TPqbeI7SYXbwnqM=

On Thu, Apr 2, 2009 at 6:20 AM, Jitse Niesen <jitse@xxxxxxxxxxxxxxxxx> wrote: > On Wed, 1 Apr 2009, Gael Guennebaud wrote: > >> let me remind that currently the packet versions of sin, cos, exp, log >> and sqrt are enabled by default (regardless of the fast-math option). >> The vectorized version of sin, cos and sqrt can be disabled by >> defining a preprocessor token. If there are good argument I'm still ok >> to change this behavior for "disabled by default" and "enabled if >> either EIGEN_FAST_MATH or _FAST_MATH_ are defined". > > I did not follow the previous discussion about the sse implementation of > sqrt in detail, but I believe the conclusion was that we're willing to lose > one or two bits of precision. That's probably no problem in the vast > majority of cases. However, it's against the IEEE floating point standard, > which says that sqrt should be computed to full precision. Thus, this is > what I'd expect sqrt to do in the default case. Of course, you may decide > otherwise, but at least stick a fat warning in the documentation. > > I'm not sure how relevant this is to your question. Perhaps not very. it is relevant. Since I'm fine with both behavior I need people express their opinion to make that change or not. So I count one vote to "disable by default unless -ffast-math is set". > Incidentally, Eigen/src/Core/GenericPacketMath.h:197 reads > > template<typename Packet> inline static Packet ei_psqrt(Packet a) > { return ei_log(a); } > > It seems weird to call ei_log in the body ... oops, fixed in rev 948062, thanks a lot. > Cheers, > Jitse > > >

**Follow-Ups**:**Re: [eigen] sse asin implementation***From:*Rohit Garg

**References**:**Re: [eigen] sse asin implementation***From:*Gael Guennebaud

**Re: [eigen] sse asin implementation***From:*Jitse Niesen

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