RE: strange problem

[THOMAS Paul Richard]

Gerald,

I am glad that the function did it for you.  As several of the respondents
said, this is a result of limitations in floating point arithmetic.

Not only is the response time of this list good but you should check out the
times of the replies and the locations of some of our friends on this list.
I sort of wonder if they have homes to go to?

Paul

-----Message d'origine-----
De : Gerald Ebberink [mailto:address@hidden
Envoyé : vendredi 28 novembre 2003 11:39
À : address@hidden
Objet : Re: strange problem


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Problem solved,
thnx all

since I don't work under windows the function gives me a nice way of
cleaning th results after each multiplication.

by the way, this list has a very low response time. Other programs have
far worse lists.

THOMAS Paul Richard wrote:
| Dear All,
|
| The matrix multiplication gives zero for ans(1,1) in octave 2.1.49 (under
| Cygwin)!  However, Matlab5 gives the same result as Gerald's.
|
| Compiling the expression 1-(100*-1)/100 in g++ or intel C++ give 0.  I
would
| conclude that this is some peculiarity of BLAS that seems to have been
| eliminated in later versions of Octave/BLAS.
|
| It seems to me that Gerald's work-around might be to use
|
| function xout=clean(xin,prec);xout=xin.*(abs(xin)>prec);endfunction;
|
| so that
|
| a=clean([1,100;0,1]*[1,0;(-1/100),1],1E-16);
|
| a(1,1) yields 0
|
| Paul
|
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- --
Ing. Gerald Ebberink
Laser Technician

Kernfysisch Versneller Instituut
Rijksuniversiteit Groningen
Zernikelaan 25
9747 AA Groningen
The Netherlands
tel: +31 50 363 3518
lab: +31 50 363 3588
fax: +31 50 363 4003


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Octave is freely available under the terms of the GNU GPL.

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-------------------------------------------------------------
Octave is freely available under the terms of the GNU GPL.

Octave's home on the web:  http://www.octave.org
How to fund new projects:  http://www.octave.org/funding.html
Subscription information:  http://www.octave.org/archive.html
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