Re: slow LU decomposiotion? for octave 4 for windows

[siko1056]

Dear Tatsuro MATSUOKA,

Do you also this performance issue for the vectorized test script in all
your versions? I see similar good results on my PC without for-loops and
Octave 4.0.1 and dev.

------------------
more off 

Num=1000;
rand('seed',1); 
A=rand(Num)-0.5; 
rand('seed',2); 
B=rand(Num,ItNum)-0.5; 
[L U P]=lu(A); 
% 
disp('Simple left division'); 
tic; 
x=A\B;  % vectorized
toc; 
x1=x(:,end); 
% 
disp('LU decomposition'); 
tic; 
c=P*B; y=L\c; x=U\y;  % vectorized
toc; 
x2=x(:,end); 
id=1:Num; 
plot(id,x1, 'o1',id,x2, '+2'); 
------------------

This would make me struggle. For-loops are slow (Rik held an excellent talk
about this at the Octconf 2015, http://wiki.octave.org/OctConf_2015) and
maybe older versions of Octave handled loops in another way?!

Regards,
Kai



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