[Scilab-users] [EXTERNAL] Re: my loop faster than vectorization (???)

[Carrico, Paul]

Hi

Interesting feedback, but different of mine :)

With n=100000 with my working station under Windows 7.0 with Scilab 5.5.2
(from memory I noticed the same behavior on my old laptop under Ubuntu 16.04 LTS)

duration1  =
    93.057
 duration2  =
    108.325
 duration3  =
    1.279
 duration3  =
    135.178


Nota: nevertheless for huge asci files containing millions of lines (not in the same format of course) , I finally decided to "outsource"  this work

Paul


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De : users [mailto:users-bounces at lists.scilab.org] De la part de Alexis Cros
Envoyé : vendredi 30 juin 2017 12:33
À : Users mailing list for Scilab
Objet : [EXTERNAL] Re: [Scilab-users] my loop faster than vectorization (???)


Hi,

On my computer came, in order of rapidity, 1st case, 2nd, 4th then 3rd

 duration1  =

   0.1907777

 duration2  =

   0.2304603

 duration3  =

   23.275328 wow!

 duration4  =

   0.2531153

We may compare who has the best computer ^^

Le 29/06/2017 à 09:56, Carrico, Paul a écrit :
Here is the correct code - loop faster here (68 time faster with n = 100 000)

I'm confuse

Paul
#############################################################
mode(0)
clear

n = 10000;
lower_bound = 0.1*n;
upper_bound = 0.6*n;

a = rand(n,1);
b = string(a);

// case 1 : eval on each row

tic();

i=1:(upper_bound-lower_bound+1)';

c(i,1) = zeros((upper_bound-lower_bound+1),1);

c(i,1) = eval(b(lower_bound:upper_bound,1));

duration1 = toc()

// case 2 : eval on the complete matrix
tic();
d = zeros((upper_bound-lower_bound+1),1);
d = string(d);
d = b(lower_bound:upper_bound,1);
d = eval(d);
duration2 = toc()

// case 3 :with an uggly loop
tic();
e = zeros((upper_bound-lower_bound+1),1);
for i = 1 : (upper_bound - lower_bound+1)
    e(i,1) = eval(b(i+lower_bound-1,1));
end
duration3 = toc()

// case 4 :with an uggly loop (eval on the complete matrix)
tic();
f = zeros((upper_bound-lower_bound+1),1);
f = string(f);
for i = 1 : (upper_bound - lower_bound)
    f(i,1) = b(i+lower_bound-1,1);
end
f = eval(f);
duration3 = toc()


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De : users [mailto:users-bounces at lists.scilab.org] De la part de Carrico, Paul
Envoyé : jeudi 29 juin 2017 09:29
À : International users mailing list for Scilab. (users at lists.scilab.org<mailto:users at lists.scilab.org>)
Objet : [EXTERNAL] [Scilab-users] my loop faster than vectorization (???)

Hi all

I'm facing a case where a loop is faster than vectorization (at least I hope I'm using vectorization) ... I'm necessarily doing something wrong but I don't see what

Hope somebody will point out my mistake

Thanks for your time

Paul

################################################
mode(0)
clear

n = 10000;
lower_bound = 0.1*n;
upper_bound = 0.6*n;

a = rand(n,1);
b = string(a);

// case 1 : eval on each row
tic();
c = zeros((upper_bound-lower_bound),1);
c(1:(upper_bound-lower_bound),1) = eval(b(1:(upper_bound-lower_bound),1));
duration1 = toc()

// case 2 : eval on the complete matrix
tic();
d = zeros((upper_bound-lower_bound),1);
d = string(d);
d = b([1:(upper_bound-lower_bound)],1);
d = eval(d);
duration2 = toc()

// case 3 :with an uggly loop
tic();
e = zeros((upper_bound-lower_bound),1);
for i = 1 : (upper_bound - lower_bound)
    e(i,1) = eval(b(i+lower_bound-1,1));
end
duration3 = toc()

// case 4 :with an uggly loop (eval on the complete matrix)
tic();
f = zeros((upper_bound-lower_bound),1);
f = string(f);
for i = 1 : (upper_bound - lower_bound)
    f(i,1) = b(i+lower_bound-1,1);
end
f = eval(f);
duration3 = toc()

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