[petsc-users] Petsc has generated inconsistent data - Divide by zero!
TAY wee-beng
zonexo at gmail.com
Sat Jul 9 17:21:49 CDT 2011
Hi Jed,
I have attached the output runing under linux. It's only running with 1
processor. I am using runge kutta 3rd order to solve my problem, so
there's 3 substeps per time step ie I need to solve the x/y momentum
eqns 3 times per time step.
The error occurs at t=2, substep=2. It stated in the output.
Btw, I am solving the x and y momentum eqns separately, since they are
independent of one another. How can I solve it together?
My code is:
call
MatSetValues(A_semi_x,1,II,1,JJ,semi_mat_x(k,kk),INSERT_VALUES,ierr) ...
call MatAssemblyBegin(A_semi_x,MAT_FINAL_ASSEMBLY,ierr)
call MatAssemblyEnd(A_semi_x,MAT_FINAL_ASSEMBLY,ierr)
call KSPGetPC(ksp_semi_x,pc_semi_x,ierr)
ksptype=KSPBCGS
call KSPSetType(ksp_semi_x,ksptype,ierr)
call KSPSetFromOptions(ksp_semi_x,ierr)
tol=1.e-5
call
KSPSetTolerances(ksp_semi_x,tol,PETSC_DEFAULT_DOUBLE_PRECISION,PETSC_DEFAULT_DOUBLE_PRECISION,PETSC_DEFAULT_INTEGER,ierr)
exactly the same for y...
call VecAssemblyBegin(b_rhs_semi_x,ierr)
call VecAssemblyEnd(b_rhs_semi_x,ierr)
call VecAssemblyBegin(xx_semi_x,ierr)
call VecAssemblyEnd(xx_semi_x,ierr)
call KSPSetOperators(ksp_semi_x,A_semi_x,A_semi_x,SAME_NONZERO_PATTERN,ierr)
call KSPSolve(ksp_semi_x,b_rhs_semi_x,xx_semi_x,ierr)
call KSPGetConvergedReason(ksp_semi_x,reason,ierr)
exactly the same for y...
Thanks alot!
Yours sincerely,
TAY wee-beng
On 9/7/2011 12:26 AM, Jed Brown wrote:
> On Fri, Jul 8, 2011 at 17:17, TAY wee-beng <zonexo at gmail.com
> <mailto:zonexo at gmail.com>> wrote:
>
> Hi Jed,
>
> This is my output when the error happens for gmres:
>
> 2 KSP preconditioned resid norm 1.556688898463e+007 true resid
> norm 2.58995443
> 8801e+003 ||Ae||/||Ax|| 1.232088736212e+003
> 2 KSP preconditioned resid norm 1.556688898463e+007 true resid
> norm 2.58995443
> 8801e+003 ||Ae||/||Ax|| 1.232088736212e+003
> 3 KSP preconditioned resid norm 1.207952812560e+003 true resid
> norm 9.05939430
> 1179e+003 ||Ae||/||Ax|| 4.309719703237e+003
> 3 KSP preconditioned resid norm 1.207952812560e+003 true resid
> norm 9.05939430
> 1179e+003 ||Ae||/||Ax|| 4.309719703237e+003 3 KSP preconditioned
> resid norm 1.207952812560e+003 true resid norm 9.05939430
> 1179e+003 ||Ae||/||Ax|| 4.309719703237e+003
> 3 KSP preconditioned resid norm 1.207952812560e+003 true resid
> norm 9.05939430
> 1179e+003 ||Ae||/||Ax|| 4.309719703237e+003
> 3 KSP preconditioned resid norm 1.207952812560e+003 true resid
> norm 9.05939430
> 1179e+003 ||Ae||/||Ax|| 4.309719703237e+003
> 4 KSP preconditioned resid norm 3.815055004710e+001 true resid
> norm 1.96385966
> 1729e+002 ||Ae||/||Ax|| 9.342439899591e+001
> 4 KSP preconditioned resid norm 3.815055004710e+001 true resid
> norm 1.96385966
> 1729e+002 ||Ae||/||Ax|| 9.342439899591e+001
> 4 KSP preconditioned resid norm 3.815055004710e+001 true resid
> norm 1.96385966
> 1729e+002 ||Ae||/||Ax|| 9.342439899591e+001
> 4 KSP preconditioned resid norm 3.815055004710e+001 true resid
> norm 1.96385966
> 1729e+002 ||Ae||/||Ax|| 9.342439899591e+001
> 4 KSP preconditioned resid norm 3.815055004710e+001 true resid
> norm 1.96385966
> 1729e+002 ||Ae||/||Ax|| 9.342439899591e+001
>
>
> Why is the same line output multiple times? Do you have an MPI problem?
>
> This convergence looks funky; I suspect your preconditioner is
> singular and/or nonlinear. Please send -ksp_view output as you are
> running here and with -pc_type asm -sub_pc_type lu.
>
>
> for fgmres:
>
> 34 KSP preconditioned resid norm 2.428114102327e-005 true resid
> norm 3.35941610
> 6265e-005 ||Ae||/||Ax|| 1.598129588716e-005
> 34 KSP preconditioned resid norm 2.428114102327e-005 true resid
> norm 3.35941610
> 6265e-005 ||Ae||/||Ax|| 1.598129588716e-005
> 35 KSP preconditioned resid norm 2.200715659545e-005 true resid
> norm 3.88294769
> 5703e-005 ||Ae||/||Ax|| 1.847182191086e-005
> 35 KSP preconditioned resid norm 2.200715659545e-005 true resid
> norm 3.88294769
> 5703e-005 ||Ae||/||Ax|| 1.847182191086e-005
> 35 KSP preconditioned resid norm 2.200715659545e-005 true resid
> norm 3.88294769
> 5703e-005 ||Ae||/||Ax|| 1.847182191086e-005
> 35 KSP preconditioned resid norm 2.200715659545e-005 true resid
> norm 3.88294769
> 5703e-005 ||Ae||/||Ax|| 1.847182191086e-005
> 35 KSP preconditioned resid norm 2.200715659545e-005 true resid
> norm 3.88294769
> 5703e-005 ||Ae||/||Ax|| 1.847182191086e-005
> 36 KSP preconditioned resid norm 2.011575409369e-005 true resid
> norm 3.89282805
> 6204e-005 ||Ae||/||Ax|| 1.851882441357e-005
> 36 KSP preconditioned resid norm 2.011575409369e-005 true resid
> norm 3.89282805
> 6204e-005 ||Ae||/||Ax|| 1.851882441357e-005
> 36 KSP preconditioned resid norm 2.011575409369e-005 true resid
> norm 3.89282805
> 6204e-005 ||Ae||/||Ax|| 1.851882441357e-005
> 36 KSP preconditioned resid norm 2.011575409369e-005 true resid
> norm 3.89282805
> 6204e-005 ||Ae||/||Ax|| 1.851882441357e-005
> 36 KSP preconditioned resid norm 2.011575409369e-005 true resid
> norm 3.89282805
> 6204e-005 ||Ae||/||Ax|| 1.851882441357e-005
>
> Btw, I am solving the x and y momentum eqns so there 's 2 eqns to
> solve.
>
>
> Do you solve them separately or both at once? (We usually recommend
> the latter.)
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