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

[Patrick Alken]

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.

Patrick

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:
>
> > Hello,
> >
> > 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,
> > Victor