[petsc-users] ODE solving

[Xuan Yu]

Hi


I am using Petsc solve ODE nonlinear problem.

I was told to use direct method: umfpackage because of the jacobian matrix is 1860 by 1860.

But the time consumption is still too big:

TSSetType(ts,TSBEULER)

time ./pihm -log_summary -ksp_type preonly -pc_type lu -pc_factor_mat_solver_package umfpack

I got the result:
 
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When I use TSSetType(ts,TSSUNDIALS), it is fast:

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How can I find the reason why BEULER is so slow?

Thanks

Xuan