[petsc-users] about snes

[陈乐平（Leping Chen）]

petsc teams,

When I use SNES, I find my program iterated many times but x vector and residual vector

remained unchanged, that is to say,no convergence.I used finite difference jacobian approximations,

but I cannot confirm the jacobian matrix structure is right.Whether the matrix structure will influence

the convergence of SNES or not? Why does my x vector and residual vector remained unchanged?

      call FormJacobian(snes,x,J,J,flag,dummy,ierr)
      call MatGetColoring(J,MATCOLORING_SL,iscoloring,ierr)
      call MatFDColoringCreate(J,iscoloring,fdcoloring,ierr)
      call ISColoringDestroy(iscoloring,ierr)
      call MatFDColoringSetFromOptions(fdcoloring,ierr)
      call MatFDColoringSetFunction(fdcoloring,FormFunction,
     &   PETSC_NULL_OBJECT,ierr)
       call SNESSetJacobian(snes,J,J,SNESDefaultComputeJacobianColor,
     & fdcoloring,ierr)
      call SNESGetKSP(snes,ksp,ierr)
      call KSPGetPC(ksp,pc,ierr)
      call SNESSolve(snes,PETSC_NULL_OBJECT,petscu,ierr)
Thanks,
leping
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