Re: [eigen] (General question) Floating point: why are 'inf' and 'nan' slow? |

[ Thread Index | Date Index | More lists.tuxfamily.org/eigen Archives ]

*To*: eigen@xxxxxxxxxxxxxxxxxxx*Subject*: Re: [eigen] (General question) Floating point: why are 'inf' and 'nan' slow?*From*: Benoit Jacob <jacob.benoit.1@xxxxxxxxx>*Date*: Wed, 23 Sep 2009 10:57:15 -0400*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=ifBGl52Odk0gw5Bk1/HWvVydewRhaREWqj8xPaz5+kE=; b=HKcBWERTdH/uGFFckuf69UI5JO1dRLkQEZffjHFXedyUPESj7ofxwtIOhJZhwpxlJP g2iH6dNWnzOTU/TrkJcPqu0ytXKzZJRssWyUCRoFgdxrUyqI8CeNLyaao/6kZzMlf3c/ QRe2V0iZ6LWzF5WkVBAxknV+j/nygnUhdo9Ec=*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=RAxLWwgVOnCIwEWNdR3F4qFUC5pHfQzGzXMnw0ow+T38oOqvDNHmda9hvNhrw1L2qL N6StgkOl8kfmkEtHHCdHZmzssHt9GO7Zpt3E4/oYZR/Pda6fydiOqBVnGAma8YOzwUa0 w4TVs4CASur4rmIGfOg0/9lOHhDRiKC6s2O8o=

My program is just repeatedly computing inf*inf, so denormalized numbers can't be the explanation... Benoit 2009/9/23 Robert Bocquier <robert.bocquier@xxxxxxxxxxx>: > Benoit Jacob a écrit : >> Hi, >> >> Sorry for adding to the currently already high traffic here. >> >> Here, on linux / x86, my programs run 100x slower when the >> floating-point values are 'inf' or 'nan'. >> >> Only scalar code is affected, SSE code is not affected. >> >> I haven't enabled floating-point exception signals. I don't have a FP >> signal handler. Just any basic c++ program. >> >> Can this be "fixed"? How? >> >> Otherwise, I really need to make sure that solve() methods avoid >> producing such special values when no solution exists --- otherwise >> they take much longer to return. >> >> Thanks for your help, >> Benoit >> >> >> >> > Hi Benoit, > may be *before* arriving to those extremes you've encountered > "denormalized numbers" ? > There are provisions to get rid of them with SSE, while in regular "387" > code you must explicitly deal with them. This is consistent with your > observation (but it's not a proof). > > Best, > -- > Robert Bocquier > > > ARTURIA > 4 chemin de Malacher > 38240 Meylan - France > Tel: +33 438 020 555 > Fax: +33 438 020 525 > > http://www.arturia.com > > > > >

**References**:**[eigen] (General question) Floating point: why are 'inf' and 'nan' slow?***From:*Benoit Jacob

**Re: [eigen] (General question) Floating point: why are 'inf' and 'nan' slow?***From:*Robert Bocquier

**Messages sorted by:**[ date | thread ]- Prev by Date:
**Re: [eigen] (General question) Floating point: why are 'inf' and 'nan' slow?** - Next by Date:
**Re: [eigen] (General question) Floating point: why are 'inf' and 'nan' slow?** - Previous by thread:
**Re: [eigen] (General question) Floating point: why are 'inf' and 'nan' slow?** - Next by thread:
**Re: [eigen] (General question) Floating point: why are 'inf' and 'nan' slow?**

Mail converted by MHonArc 2.6.19+ | http://listengine.tuxfamily.org/ |