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Re: [Help-gsl] eigen test fails on 32-bit (x86) Linux

From: Patrick Alken
Subject: Re: [Help-gsl] eigen test fails on 32-bit (x86) Linux
Date: Mon, 18 Aug 2014 13:21:17 -0600
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.7.0

GSL is already sorting the eigenvalues based on magnitude, so the problem seems to be that with the extra -O3 optimization, the gsl_eigen_gen and gsl_eigen_genv routines are producing slightly different results, leading to a different sorting order. One way to fix this would be to sort by real part first and then by imaginary part, but it may be a little while until I can look into this further.


On 08/18/2014 12:59 PM, Martin Jansche wrote:
I'm not sure if GSL makes any guarantees about the direction of
eigenvectors. It looks like the test might pass if one only looks at the
magnitude of the values. Perhaps the test could be made robust against sign
changes by looking at absolute values.

On Mon, Aug 18, 2014 at 1:53 PM, address@hidden <
address@hidden> wrote:


I noticed that eigen test fails on 32-bit Linux (x86) when compiled with
-O3 flag:

$ ./configure CFLAGS="-O3"
$ make
$ eigen/test
FAIL: gen, direct eigenvalue(4) imag, random (-0.481216772353650846
observed vs 0.481216772353650846 expected) [877968]
FAIL: gen, direct eigenvalue(5) imag, random (0.481216772353650901 observed
vs -0.481216772353650846 expected) [877970]
FAIL: gen, direct eigenvalue(15) imag, random (6.85872455924790447 observed
vs -6.85872455924790536 expected) [877990]
FAIL: gen, direct eigenvalue(16) imag, random (-6.85872455924790536
observed vs 6.85872455924790625 expected) [877992]

I'm using GSL version 1.16, 32-bit Ubuntu 10.04 and GCC 4.4.3.

Best regards,

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