[Scilab-users] [EXTERNAL] Re: Vectorization issue

[Rafael Guerra]

Hi Paul,
 
‘b’ seems to be already used in the Km and Km2 formulas and so, it cannot be
used at the same time as an auxiliary variable with different meaning.
Only ‘b’ needs to be changed.
 
Regards,
Rafael
 
From: users [mailto:users-bounces at lists.scilab.org] On Behalf Of Carrico, Paul
Sent: Thursday, May 26, 2016 12:38 PM
To: 'Users mailing list for Scilab' <users at lists.scilab.org
<mailto:users at lists.scilab.org> >
Subject: Re: [Scilab-users] [EXTERNAL] Re: Vectorization issue
 
Thanks Rafael for the answer
 
One explanation of the error is that I used a and b letter instead of aa and bb
in your example; your code, if I change aa -> a and bb -> it fails again 
 why ?
(I do not understand)
 
 
De : users [mailto:users-bounces at lists.scilab.org] De la part de Rafael Guerra
Envoyé : jeudi 26 mai 2016 12:26
À : 'Users mailing list for Scilab'
Objet : [EXTERNAL] Re: [Scilab-users] Vectorization issue
 
 
Hi Paul,
 
It seems that there may be some issues with the .*, .^ syntax and also the use
of the same variable in different context (b).
 
Editing the vectorization part of your code as follows:
 
// using vectorization
aa = [0:n]';
bb = ones(n,1);
i = aa.*.bb;
j = bb.*.aa;
 
Km2 = zeros(n*(n+1),1);
Km2 = %pi^6*((2*i+1).^2 .* j.^2).*((2*i+1).^2.*(b/2*d)^2 + j.^2) ;
Km2 = (144*(b/d).^4)/ sum(Km2);
Km2 = 1.2 + (nu/(1+nu))*Km2;
k2 = 1/Km2
 
produces:
   k  =    0.8333090  
   k2  =  0.8333333  
 
A small difference. I did not check the formulas but it might be numerical error
only.
 
Regards,
Rafael
 
From: users [mailto:users-bounces at lists.scilab.org] On Behalf Of Carrico, Paul
Sent: Thursday, May 26, 2016 11:30 AM
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Subject: [Scilab-users] Vectorization issue
 
Dear
I failed in using vectorization in the example immediately bellow; but I do not
remember if it’s possible : any advice ?
Thanks
Paul
############################
mode(0)
n = 20
Km = 0;
b = 100;
d = 20;
nu = 0.3;
 
// using loops
for i = 0 : n
    for j = 1 : n
        Km = Km + (144*(b/d)^4)/(  %pi^6*(2*i+1)^2*j^2*((2*i+1)^2*(b/2*d)^2+j^2)
);
    end
end
 
Km = 1.2 + (nu/(1+nu))*Km
k = 1/Km
 
// using vectorization
a = [0:n]';
b = ones(n,1);
i = a.*.b;
j = b.*.a;
 
Km2 = zeros(n*(n+1),1);
Km2 = (  %pi.^6*((2*i+1).^2. * j.^2)*((2*. i+1).^2*(b/2*d).^2 + j^2)  )
Km2 = (144*(b/d).^4)/ Km2
Km2 = 1.2 + (nu/(1+nu))*Km2
k2 = 1/Km2
 
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