Re: Failed test in linsolve.m

[Marco Atzeri]

On 4/2/2015 8:35 AM, Julien Bect wrote:
> Dear all,
>
> Here the result I get when compiling from hg changeset 185e8dbdaa40
> (very recent) on a Debian wheezy (7.8) x86_64 machine with "./configure
> --without-OSMesa":
>
> Summary:
>
>    PASS     12873
>    FAIL         1
>    XFAIL       14
>    SKIPPED     96
>
> The log for the failed test is:
>
>  >>>>> processing
> /usr/local/src/octave/default/scripts/linear-algebra/linsolve.m
> ***** test
>   n = 4;
>   A = triu (rand (n));
>   x = rand (n, 1);
>   b = A' * x;
>   opts.UT = true;
>   opts.TRANSA = true;
>   assert (linsolve (A, b, opts), A' \ b);
> !!!!! test failed
> ASSERT errors for:  assert (linsolve (A, b, opts),A' \ b)
>
>    Location  |  Observed  |  Expected  |  Reason
>      (1)        0.42063      0.42063      Abs err 5.5511e-17 exceeds tol 0
>      (2)        0.68722      0.68722      Abs err 4.1078e-15 exceeds tol 0
>      (3)        0.25533      0.25533      Abs err 2.1094e-15 exceeds tol 0
>      (4)        0.52907      0.52907      Abs err 7.3275e-15 exceeds tol 0
>
> Has anybody seen this ? Perhaps should we introduce a tolerance for
> these tests ?


a zero tolerance is seldom a good idea.
It should be several eps as minimum.


> @++
> Julien