Hello,
This problem is fixed in Scilab 6.1
S.
Le 06/02/2020 à 08:30, Federico Miyara a écrit :
Dear all,
Trying to implement sine integral from the series, my first attempt
y = 0
N = 30;
for n=0:N
y = y + (-1)^n * x.^(2*n+1)./(2*n+1)./factorial(2*n+1);
end
works fine for x<20. Now I want to vectorize it so the plan is to
create a polynomial and then apply horner. The coefficients are
coe = (-1).^(0:N)./(1:2:2*N+1)./factorial(1:2:2*N+1)
I get
coe =
column 1 to 6
1. -0.055555555556 0.001666666667 -0.000028344671
0.000000306192 -0.000000002277
column 7 to 19
0.000000000012 -5.09810915D-14 1.65379838D-16 0. 0. 0.
0. 0. 0. 0. 0. 0. 0.
column 20 to 31
0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.
From the 10-th coefficient on, the value seems to be 0. However,
coe(10) yields 9.32044813D-22
Actually this is a documented behavior (it is described in hhe format
help page). But I wonder if it is advisable, since it may be confusing.
Indeed, it took me some time to discover that the coefficients were
stored as floating point. At the beginning I "believed" what I saw and
started to think which would be the best order of the operations to
avoid too small intermediate values.
Is there a reason for that behavior that outweighs the inconvenience
I've mentioned?
Regards,
Federico Miyra
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--
Stéphane Mottelet
Ingénieur de recherche
EA 4297 Transformations Intégrées de la Matière Renouvelable
Département Génie des Procédés Industriels
Sorbonne Universités - Université de Technologie de Compiègne
CS 60319, 60203 Compiègne cedex
Tel : +33(0)344234688
http://www.utc.fr/~mottelet
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