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Re: slow LU decomposiotion? for octave 4 for windows
From: |
siko1056 |
Subject: |
Re: slow LU decomposiotion? for octave 4 for windows |
Date: |
Tue, 31 May 2016 05:07:41 -0700 (PDT) |
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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