Re: [eigen] SSE square root |

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*To*: eigen@xxxxxxxxxxxxxxxxxxx*Subject*: Re: [eigen] SSE square root*From*: Benoit Jacob <jacob.benoit.1@xxxxxxxxx>*Date*: Fri, 27 Mar 2009 14:39:00 +0100*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=CVyCW/PRztHlZA9Y7sNhkQjZco6jr8w+wMKyJ/XmWF8=; b=a2c4W6PeVwzUY61Yy3maLqYUkCIfGpjNKQum1ds3Waaqq0YwuhkcqxmQumvrjyYfxV ZuFRMxvtznSYljyFee3sytSdrspkd+kYIYRjsMMDvmWI6dSj16X2F6VF+mAkfdddh5Tj CzBibE7N3qMUdDMk6XXgVahTq7peWCleYGx/I=*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=quhO68TczMGTl+erUHa2p3QGWRQahI7cwfKMDfHmxquVzIMSnz7/WwYV+Ojo0biAUC HoMNBARe+zQmbNmuWtTgyyF5Q2oHVSw9Jpkd/CgiNkV1xbebKw66faKLpOVwbSBzKObd bm57Zy6XIu1TLSY36x7Pcum7+5igDqZKtoMYY=

2009/3/27 Gael Guennebaud <gael.guennebaud@xxxxxxxxx>: > On Fri, Mar 27, 2009 at 1:39 PM, Rohit Garg <rpg.314@xxxxxxxxx> wrote: >>> hm, sorry that's not entirely true. I increased the number of samples, >>> and for the fastest version: >>> >>> 1 iter = 42% of failures with max error = 2.78308e-07 >>> 2 iter = 36% of failures with max error = 2.15188e-07 >>> 3 iter = 34% of failures with max error = 1.87297e-07 >> >> Failure? Do you mean that the error blows up for these values? But the >> max error is pretty low. At any rate, the increased precision is too >> low to iterate again compared to the perf hit, IMHO. > > don't panic, failure means error>0 OK, then indeed, the 2nd newton step is really not worth it. The reason why it doesn't improve accuracy as much as theoretically, must be that we are too close to the floating point numbers precision already. Then, it seems to me that we can declare the precision to be sufficient, as after the user will do a few operations on these numbers, he will fall to a similar level of precision anyway. Cheers, Benoit

**References**:**[eigen] SSE square root***From:*Rohit Garg

**Re: [eigen] SSE square root***From:*Rohit Garg

**Re: [eigen] SSE square root***From:*Gael Guennebaud

**Re: [eigen] SSE square root***From:*Rohit Garg

**Re: [eigen] SSE square root***From:*Gael Guennebaud

**Re: [eigen] SSE square root***From:*Benoit Jacob

**Re: [eigen] SSE square root***From:*Gael Guennebaud

**Re: [eigen] SSE square root***From:*Gael Guennebaud

**Re: [eigen] SSE square root***From:*Rohit Garg

**Re: [eigen] SSE square root***From:*Gael Guennebaud

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