ode45 too long to solve

hi , i'm trying to solve an ode , my program works but it makes 1 hours... and o don't understand why

Here is my fonction to define my ode :

function  dy=f_mixte(t,y)

global Q  b   K n E sg0 epoint C1 C2 D1 D2 

f=abs(y(1)-y(3)-y(4))-Q*(1-exp(-b*y(2)))-sg0;

if f<0

      dy(2)=0;

else

      dy(2)=(f/K).^n;

end

dy(5)=sign(y(1)-y(3)-y(4));

dy(1)=E*(epoint-dy(5));

dy(3)=C1*dy(5)-D1*y(3)*dy(2);

dy(4)=C2*dy(5)-D2*y(4)*dy(2);

dy=dy';

end

And here my main function :

global Q  b   K n E sg0 epoint C1 C2 D1 D2 sigma0

b=5;

Q=-150 ;

E=140000;

sigma0=200;

K=800;

n=6;

epoint=0.001;

sg0=200;

C1=300000;

C2=25000;        

D1=2000;                 

D2=200;

[T,a]=ode45('f_mixte',[0 10],[0 0 0 0 0])

thanks for your help :)

[Merged information from duplicate Question]

hi !

I would like to improve my program, i'm want it be faster and make better virtual mode memory management :

global Q  b   K n E sg0 epoint C1 C2 D1 D2 

b=5;

Q=-150 ;

E=140000;

sigma0=200;

K=800;

n=6;

epoint=0.001;

C1=300000;

C2=25000;

D1=2000;

D2=200;

sg0=200;

%Resolution 

[t,y]=ode45('f_mixte',[0 10],[0 0 0 0 0]);

sigma1=y(:,1);
ep1=y(:,5);
e1=ep1+sigma1/E;

tic

hold on 

for w = 0:100

Ti=10;

Tf=30;

L=length(y);

epoint=-epoint;

[t,y]=ode45('f_mixte',[Ti Tf],[y(L,:)]);

Ti=Tf;

Tf=Ti+20;

sigma2=y(:,1);

ep2=y(:,5);

e2=ep2+sigma2/E;

L=length(y);

plot(e1,sigma1,e2,sigma2)

end

hold off

toc

and my main function

function  dy=f_mixte(t,y)

global Q  b   K n E sg0 epoint C1 C2 D1 D2 

R=Q*(1-exp(-b*y(2)));

f=abs(y(1)-y(3)-y(4))-R-sg0;

if f<0

      dy(2)=0;

else

      dy(2)=(f/K)^n;

end

dy(5)=sign(y(1)-y(3)-y(4))*dy(2);

dy(1)=E*(epoint-dy(5));

dy(3)=C1*dy(5)-D1*y(3)*dy(2);

dy(4)=C2*dy(5)-D2*y(4)*dy(2);

dy=dy';

end

[Jan]

Please answer the questions for clarifications instead of posting new questions about the same problem. See http://www.mathworks.com/matlabcentral/answers/59695-loop-for-with-ode45 .

And please, tony, format your code properly. Now Walter did this for you.

Answer 1

[Jan]

I've explained problems with integrating discontinuous functions in your former thread http://www.mathworks.com/matlabcentral/answers/59582-ode45-errer-input-argument-y-is-undefined already. Asking equivalent questions repeatedly while ignoring answers does not help to find a solution.

Answer 2

[tony]

sorry , but here it's the same problem. My last problem is solved. But here the problem is a little more complex.

[Jan]

You still have a discontinuity in the function, which you want to integrate. My former comment explained, why this can lead to a very slow and very inaccurate calculation. Now you ask for a very slow calculation, therefore I'm not convinced, that the former problem is solved.

And if it is really solved, please explain this in the other thread also, such that nobody wastes time by creating a new suggestion anymore. Tony, please use this forum with care and respect.