Re: QR test failure with --enable-64

[Jaroslav Hajek]

2010/2/19 John W. Eaton <address@hidden>:
> On 19-Feb-2010, Jaroslav Hajek wrote:
>
> | On Fri, Feb 19, 2010 at 6:19 PM, John W. Eaton <address@hidden> wrote:
> | > When I compile Octave with --enable-64 on an amd64 system, the
> | > following test from qr.cc fails because the computed norm is exactly
> | > equal to 10*eps.  On the same system without --enable-64, the test
> | > passes.  I don't know exactly why changing the  size of integer
> | > indexes would change the result.  My best guess is that the additional
> | > memory required by the index values forces the compiler to store some
> | > floating point values that are otherwise kept in registers.
> |
> | Interesting. Is it just qrdelete that makes the difference, or is the
> | qr result also different?
>
> The test I quoted in the original message is the only one in qr.cc
> that is failing for me with --enable-64.
>

Yes, I understand that, I'm just wondering whether by
 [Q,R] = qr(AA);
you get the same Q and R with both configurations, or whether the
difference occurs in qrdelete, or maybe in the residual computation.

-- 
RNDr. Jaroslav Hajek, PhD
computing expert & GNU Octave developer
Aeronautical Research and Test Institute (VZLU)
Prague, Czech Republic
url: www.highegg.matfyz.cz