Hello,
Le 28/06/2018 à 17:41, Stéphane Mottelet a écrit :
Hello all,
A fix proposal is under review @
https://codereview.scilab.org/#/c/20204/2, in order to consider the
actual behavior of clean() when the argument has some infinite values:
In Scilab 6.0.1:
--> clean([%inf 1])
ans =
0. 0.
By a argument of continuity, since
--> clean([1.79e308 1])
ans =
1.79D+308 0.
the fixed behavior would be
--> clean([%inf 1])
ans =
Inf 0.
Please give your opinion if you feel concerned.
IMO, setting to zero all finite values of an array as soon as one of
them is %inf is abusive and counter-productive.
Let
--> A = 10.^grand(4,4,"unf",-10,5); A(2,2) = %inf;
A =
4.3699094 0.0000014 0.67061 6.095D-09
6503.1214 Inf 4.5767598 0.0006926
20.907407 1.5687011 2.749D-08 0.0029886
129.70759 1.102D-10 0.4564722 40.621591
The proposed implementation would lead to
--> clean(A) // A(abs(A)~=%inf & A==A)=0
ans =
0. 0. 0. 0.
0. Inf 0. 0.
0. 0. 0. 0.
0. 0. 0. 0.
With that, no more processing or linear algebra can be done, just
getting exclusively some zeros, %inf, and Nan.
The same can be done with A(abs(A)~=%inf) = 0. This is a poor and
stopping result.
Instead, cleaning values *with respect to the max |finite| one* will yield
--> clean(A) // B = A; A(abs(A)<max(A(abs(A)<%inf))*1e-10)=0
A =
4.3699094 0.0000014 0.67061 0.
6503.1214 Inf 4.5767598 0.0006926
20.907407 1.5687011 0. 0.0029886
129.70759 0. 0.4564722 40.621591
This result is a way richer. It still allows to work with it.
By the way, there is no /continuity/ from 1.79D+308 to %inf
An array may have all its |values| around and below the max 1.79D+308 by
some small factors, then arithmetic can still be possible with them, and
%inf will still be a special value with a special processing.
This is why i do not agree with the proposed clean() update.
Best regards
Samuel
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