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Re: control-2.3.51 released in package forum - please upload


From: marco atzeri
Subject: Re: control-2.3.51 released in package forum - please upload
Date: Mon, 04 Jun 2012 18:56:16 +0200
User-agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:12.0) Gecko/20120428 Thunderbird/12.0.1

On 6/4/2012 5:37 PM, Lukas Reichlin wrote:
On 03.06.2012, at 21:45, Sergei Steshenko wrote:



I would not call your ATLAS defective. For various reasons, results from ATLAS 
and Reference BLAS/LAPACK can differ. Remember that ATLAS stands for 
_Automatically_ _Tuned_ Linear Algebra Software :-)

Your results from the failing tests are probably not wrong: Just compare the 
observed and the expected state-space models. There are several ways to do this:
- poles and zeros should be the same
- Hankel singular values should be the same
- plots from time and frequency responses look the same
- solve the equations below for the diagonal transformation matrix T, its 
entries should be -1 and 1. (Because in your example, the absolute values are 
the same)

Aexp = T \ Aobs * T
Bexp = T \ Bobs
Cexp =      Cobs * T

To sum up: if there is a state transformation between observed and expected 
model, your results are correct.

Remember that the SLICOT authors recommend reference BLAS/LAPACK and use it for 
their test cases (which I use for test_control). If confidence in correct 
results is more important to you than a few milliseconds speed advantage from 
automatic tuning, then you should follow their advice.

Hope this helps,
Lukas


Lukas,
I had same of Sergei's faults (2 of 3) and I am using the
reference blas/lapack 3.4.1

I expect a package test function to behave reasonable correctly
for most of the system. Borderline case or alternative valid solution
should be avoided.

Regards
Marco


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