On 9/3/2012 12:03 PM, Lukas Reichlin wrote:
> On 03.09.2012, at 10:39, Rafael Laboissiere <raf...@laboissiere.net> wrote:

> Hi Rafael,
>
> You can check whether the observed and expected results are equivalent 
> state-space models (i.e. state-transformation, see command prescale for 
> formulae). This can be done, e.g., by inspection of the Hankel singular 
> values (command hsvd), time response (step, impulse) or frequency response 
> (sigma).
> If they are the same, there should be nothing to worry about. If you want the 
> same results, use Reference BLAS (and LAPACK) from www.netlib.org instead of 
> ATLAS which you are probably using. The SLICOT authors recommend the use of 
> the reference implementations. Correct results are more important than minor 
> speed advantages of automatically tuned linear algebra software, aren't they? 
> :-)
>
> Regards,
> Lukas
>

Lukas,
there is no guarantee to have the "expected" result
also with the reference lib.

Using Lapack 3.4.1 on cygwin


  test /home/marco/octave/control-2.3.53/@lti/minreal.m
   ***** assert (Ar, Ae, 1e-4);
!!!!! test failed
assert (Ar,Ae,1e-4) expected
    1.00000  -0.03930  -0.09800  -0.10660   0.07810  -0.23300   0.07770
    0.00000   1.03120   0.27170   0.26090  -0.15330   0.67580  -0.35530
    0.00000   0.00000   1.38870   0.66990  -0.42810   1.63890  -0.76150
    0.00000   0.00000   0.00000  -1.21470   0.24230  -0.97920   0.47880
    0.00000   0.00000   0.00000   0.00000  -1.05450   0.50350  -0.27880
    0.00000   0.00000   0.00000   0.00000   0.00000   1.63550  -0.43230
    0.00000   0.00000   0.00000   0.00000   0.00000   0.00000   1.00000
but got
    1.00000   0.03935   0.09802  -0.10656   0.07805  -0.23302   0.07773
    0.00000   1.03122   0.27169  -0.26093   0.15327  -0.67578   0.35529
    0.00000   0.00000   1.38869  -0.66991   0.42806  -1.63894   0.76153
    0.00000   0.00000   0.00000   1.21467  -0.24232   0.97919  -0.47884
    0.00000   0.00000   0.00000   0.00000   1.05454  -0.50348   0.27881
    0.00000   0.00000   0.00000   0.00000   0.00000   1.63547  -0.43234
    0.00000   0.00000   0.00000   0.00000   0.00000   0.00000   1.00000
maximum absolute error 3.27784 exceeds tolerance 0.0001

so we need to define a different test methodology

Regards
Marco


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