[Scilab-users] The numderivative function consumes a lot of time

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Hermes Hermes
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[Scilab-users] The numderivative function consumes a lot of time

Hi;
The numderivative function consumes a lot of time in the calculations.
In the following script I show two options for my "odes" function
In one of them I use the numderivative function; and the calculation is
extended by 9 minutes. And in the other I use the Jacobian determinant of
the function, for each variable, obtained in wxMaxima. And the calculation
is a few, few, seconds.
I am interested in using the function with numderivative, and very similar
to how I have developed it, since it allows me to use it for systems of more
equations.

//Draghilev's Method
clc;
clear;
function Sys=Q(x)
Sys(1)=(x(1)-2)^2+(x(2)-2)^2+x(3)^2-9;
Sys(2)=x(1)^6+x(2)^6+x(3)^6-12;
Sys(3)=x(3);
endfunction
[j,v,info]=fsolve([2;-0.1;3],Q)
ics=j;
//
N=100;
smin=0.0;
smax=0.046;
h=0.001;
*function [dydt]=odes(t,x)
//Scilab
gfd=numderivative(Q,x);
[r,c]=size(gfd)
ic=1:c
for i=1:c
dydt(i)=(-1)^i*det(gfd(1:$-1,find(ic~=i)));  
end
endfunction
*
//from wxMaxima
function dydt=odes(t,x)
    //dydt=zeros(x);
    dydt(1)=-12*(x(2)-2)*x(3)^5+12*x(2)^5*x(3)
    dydt(2)=12*(x(1)-2)*x(3)^5-12*x(1)^5*x(3)
    dydt(3)=-12*(x(1)-2)*x(2)^5+12*x(1)^5*(x(2)-2)
endfunction

    step=smax/N;
    t=[smin:step:smax*N];
    t0=0
    atol=h/100000;
    LL= ode( ics,t0, t,atol,odes)
    clf;
    drawlater()
    param3d(LL(3,:)',LL(2,:)',LL(1,:)');
   
set(gce(),"mark_mode","on","mark_style",2,"mark_size_unit","point","mark_size",4,"line_mode","off")
    drawnow()

Is it possible to decrease the calculation time if I manipulate the options
of% ODEOPTIONS = [*, ..., *]?
What parameters would I manipulate?

Gracias





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