How many times the program is run？

%%ODE45_fun解方程

tspan=[0,1e-5];

x0=[2.1e+10,1,1,1,1];

[t,x]=ode45('ODE45_fun',tspan,x0);

a1=1;a2=1;e1=9;e2=7;f1=56;f2=98;g1=76;g2=665;

a=a1+a2; e=e1+e2; f=f1+f2; g=g1+g2;

[n,m]=size(x);

for i=1:n

x(i,6)=x(i,4)*x(i,5)+x(i,2)*x(i,3)+e*f+e*g;

end

data=[t,x];

save ODE45_data.txt data -ascii

subplot(2,3,1),plot(t,x(1))

subplot(2,3,2),plot(t,x(2))

subplot(2,3,3),plot(t,x(3))

subplot(2,3,4),plot(t,x(4))

subplot(2,3,5),plot(t,x(5))

subplot(2,3,6),plot(t,x(6))

Warning: Failure at t=1.075809e-007. Unable to meet integration tolerances

without reducing the step size below the smallest value allowed (2.117582e-022) at

time t. > In ode45 at 355

[David Sanchez]

"How many times the program is run？"

What program, the number of the for-loop iterations?

[Lan]

yes， the number of the for-loop iterations. How to set up the program ?

Answer 1

[Jan]

The problem appears in the function ODE45_fun, which you did not provide. If the step size is smaller than 2.11e-22 numerical instabilities will rule the solution. Therefore ODE45 decides to stop the integration, which is much better than replying a false result.

It seem like there is an instability or jump in the function at this time. We could take a look into it, when you post the relevant code.

By the way: Providing the function to be integrated as string is a very old method. Prefer function handles like @ODE45_fun.