Re: svds test failures

[Marco atzeri]

On 8/9/2011 6:28 AM, Rik wrote:
> On 08/08/2011 08:11 PM, Liam Groener wrote:
> > On Aug 8, 2011, at 10:01 AM, Rik wrote:
> >
> > > 8/8/11
> > >
> > > Marco, Tatsuro,
> > >
> > > I've combined the list of initialization values which are acceptable for
> > > Cygwin, MinGW, and Linux and it amounts to just [35, 40].
> > >
> > > Could someone with a MacOS system try those two values in svds.m?  Below
> > > are the two lines to change.
> > >
> > > ------
> > > %! randn ('state', 35);      % Initialize to make normest function reproducible
> > > %! rand ('state', 35)
> > > ------
> > >
> > > After each change run the following code
> > >
> > > for i = 1:300
> > >   bm(i) = test ("svds");
> > > endfor
> > > sum (bm)
> > >
> > > If the sum is not 300 then neither of the values will work.
> > >
> > > --Rik
> > I haven't seen any replies yet, so I tested on OS X 10.7, Octave 3.4.2. Neither 
> > 35 nor 40 worked, 42 did.
>
> Well this is great.  Apparently there is no single value that works for all
> platforms.  The value 42 did work for Linux, Mac, and MinGW, but not for
> Cygwin.  I am going to revert to 42 since that works with the most
> platforms and then it will need to be debugged why svds is failing on Cygwin.
>
> Thanks Liam for the test on Mac platforms.
>
> --Rik

Hi Rik,

42 is fine. I will ignore the failure and put a note for myself.

As all the platform react differently changing the seed , we can assume 
one of:

1) cygwin doesn't like
    http://en.wikipedia.org/wiki/The_Hitchhiker%27s_Guide_to_the_Galaxy

2) Are rand/randn  producing different outcome on different platform ?

3) This test is on the borderline and different rounding/libraries will 
produce different outcome. Should we find a less critical matrix ?

I remember the test in the past was passing sometime with lapack and 
always with atlas. But it was before the arpack merge in octave and with 
previous gcc compiler. Eventually moving to gcc-4.5 the thing will 
change again on cygwin

Regards
Marco