[Scilab-users] Vectorization : how to proceed

[Paul Carrico]

Deer Serge,

 

Effectively it’s cleaner (and faster) to use directly vectors as arguments 

see above

B3 = list in arguments

B4 = vector in argument

 

Thanks for the recipe 
 I need to modify my code 
 LJ

 

Paul

 

/// classical function

function vect_fct2=fct_angles2(i, j)

    vect_fct2 = [ (cos(i) * sin(j) ) (-sin(j)) i j];

endfunction

 

// vectorized function

function vect_fct3=fct_angles3(i, j)

    vect_fct3 = [ (cos(i). * sin(j) ) (-sin(j)) i j];

endfunction

 

function vect_fc4t=fct_angles4(i, j)

    i=i(:);j=j(:); //transform i and j into column vectors

    vect_fct4 = [ (cos(i). *.sin(j) ), (-ones(i). *.sin(j)), i. *.ones(j),
ones(i). *. j];

endfunction

 

// traditional with loops

B2 = zeros(130321,4); n = 1

tic()

for i = 0 : 360

    for j = 0 : 360

        B2(n,:) = fct_angles2(i,j);

        n = n +1;

    end

end

time_with_loops = toc()

 

// vectorized 1

B3 = zeros(130321,4);

theta_vect = (0:360)'.*.ones(361,1);

fi_vect = (ones(361,1)'.*.[0:360])';

 

tic()

B3 = fct_angles3(theta_vect([1:130321],1),fi_vect([1:130321],1));

time_vectorization = toc()

max(abs(B2 - B3))

 

// vectorized 2

tic()

B4 = zeros(130321,4);

B4 = fct_angles3(theta_vect,fi_vect);

time2_vectorization = toc()

max(abs(B4 - B3))

 

 

De : users-bounces at lists.scilab.org [mailto:users-bounces at lists.scilab.org]
De la part de Serge Steer
Envoyé : mardi 20 novembre 2012 18:37
À : International users mailing list for Scilab.
Objet : Re: [Scilab-users] Vectorization : how to proceed

 

On 20/11/2012 17:28, Paul Carrico wrote:

Finally I think I’ve found how to proceed .. at the same time I think I
understood the use of the dot “.” (see after the cos)

 

You are right, but take care that your code will work if and only if at
least one of i or j are scalars.
If you want your code being able to work when i and j are vectors you can
use the kronecker product .*.

function vect_fct=fct_angles(i, j)

  i=i(:);j=j(:); //transform i and j into column vectors



    vect_fct3 = [ (cos(i). *.sin(j) ), (-ones(i). *.sin(j)), i. *.ones(j),
ones(i). *. j];
endfunction


Serge Steer



Paul

 

###################################################

function vect_fct=fct_angles(i, j)

    vect_fct3 = [ (cos(i). * sin(j) ) (-sin(j)) i j];

endfunction

 

B = zeros(130321,4);

theta_vect = (0:360)'.*.ones(361,1);

fi_vect = (ones(361,1)'.*.[0:360])';

 

B = fct_angles3(theta_vect([1:130321],1),fi_vect([1:130321],1));

 

 

 

 

De : users-bounces at lists.scilab.org [mailto:users-bounces at lists.scilab.org]
De la part de Paul Carrico
Envoyé : mardi 20 novembre 2012 14:34
À : 'International users mailing list for Scilab.'
Objet : [Scilab-users] Vectorization : how to proceed

 

Dear All

 

In the above example, how can I proceed to perform the product (see function
fct_angles2) ?

 

Indeed, theta are 2 vectors, so no problem for the fct_angles 
 but in case
of product, it’s naturally not work !!! what is the correct syntax in order
to use vectorization ?

 

Thanks 

 

Paul

 

######################################################

mode(0)

 

    function vect_fct=fct_angles(i, j)

        vect_fct = [cos(i)+sin(j) -sin(j) i j];

    endfunction

 

    function vect_fct2=fct_angles2(i, j)

        vect_fct = [cos(i)*sin(j) -sin(j) i j];

    endfunction

    

    

    B1 = zeros(130321,4);

    theta_vect = (0:360)'.*.ones(361,1);

    fi_vect = (ones(361,1)'.*.[0:360])';

    

    B1 = fct_angles(theta_vect([1:130321],1),fi_vect([1:130321],1));

    B2 = fct_angles2(theta_vect([1:130321],1),fi_vect([1:130321],1));

 






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