I have a very stiff combustion problem.

 I tried using ode15s to solve it. and increased the tolerances to let it solve it. But the system gives me the error Warning: Failure at t=2.330772e+12.  Unable to meet integration tolerances without reducing the step size below the smallest value
allowed (8.280564e-03) at time t.

Could anyone suggest some ways to resolve this issue?

Thank you.

[Sandip Kumar]

It seems you are running the simulation for a really long time (~ 2e12 secs), is that intended?

With respect to tolerance, you can try playing with both the tolerance values (relative and absolute), and also try reducing the step-size as well.

Also try other solver: ode23tb

[John D'Errico]

Sometime after 2e12 seconds have elapsed the problem is it is predicting the sun will either go supernova, causing a very stiff set of combustion circumstances indeed, or maybe it is just that your computer will overheat by then and catch fire.

For a more serious answer, you would certainly need to provide more detailed information. But possibly the answer is just that you are trying to solve a particularly intractable problem.