improve my program ode45

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

[Walter Roberson]

duplicates http://www.mathworks.co.uk/matlabcentral/answers/59802-ode45-too-long-to-solve