[petsc-users] my code runs too slow

[Xuan YU]

Hi,

I finite difference Jacobian approximation for my TS model. The size  
of the vector is 2500. I got the following info with(-ts_view):

  type: beuler
   maximum steps=50
   maximum time=50
   total number of nonlinear solver iterations=647
   total number of linear solver iterations=647
   SNES Object:
     type: ls
       line search variant: SNESLineSearchCubic
       alpha=0.0001, maxstep=1e+08, minlambda=1e-12
     maximum iterations=50, maximum function evaluations=10000
     tolerances: relative=1e-08, absolute=1e-50, solution=1e-08
     total number of linear solver iterations=50
     total number of function evaluations=51
     KSP Object:
       type: gmres
         GMRES: restart=30, using Classical (unmodified) Gram-Schmidt  
Orthogonalization with no iterative refinement
         GMRES: happy breakdown tolerance 1e-30
       maximum iterations=10000, initial guess is zero
       tolerances:  relative=1e-05, absolute=1e-50, divergence=10000
       left preconditioning
       using PRECONDITIONED norm type for convergence test
     PC Object:
       type: ilu
         ILU: out-of-place factorization
         0 levels of fill
         tolerance for zero pivot 1e-12
         using diagonal shift to prevent zero pivot
         matrix ordering: natural
         factor fill ratio given 1, needed 1
           Factored matrix follows:
             Matrix Object:
               type=seqaij, rows=1830, cols=1830
               package used to perform factorization: petsc
               total: nonzeros=1830, allocated nonzeros=1830
               total number of mallocs used during MatSetValues calls =0
                 not using I-node routines
       linear system matrix = precond matrix:
       Matrix Object:
         type=seqaij, rows=1830, cols=1830
         total: nonzeros=1830, allocated nonzeros=29280
         total number of mallocs used during MatSetValues calls =1830
           not using I-node routines


50 output time step takes me 11.877s. So I guess there is something  
not appropriate with my Jacobian Matrix. Could you please tell me how  
to speed up my code?

Thanks!

Xuan YU
xxy113 at psu.edu