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 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. I am using windows so I can show only part of the output. If req, I can transfer my code to linux and capture the output. Hope this explains something. Thanks! Yours sincerely, TAY wee-beng On 8/7/2011 3:34 PM, Jed Brown wrote: > On Fri, Jul 8, 2011 at 08:26, TAY wee-beng <zonexo at gmail.com > <mailto:zonexo at gmail.com>> wrote: > > [0]PETSC ERROR: KSPSolve_BCGS() line 75 in > src/ksp/ksp/impls/bcgs/C:\Codes\PETSC > -~1.1-P\src\ksp\ksp\impls\bcgs\bcgs.c > > > ierr = KSP_PCApplyBAorAB(ksp,P,V,T);CHKERRQ(ierr); /* v <- K p > */ > ierr = VecDot(V,RP,&d1);CHKERRQ(ierr); > if (d1 == 0.0) SETERRQ(PETSC_ERR_PLIB,"Divide by zero"); > > I suspect your preconditioner is singular. What options are you > running with? What happens if you use -ksp_type gmres > -ksp_gmres_restart 1000 -ksp_gmres_modifiedgramschmidt > -ksp_monitor_true_residual? Also do the same run with -ksp_type fgmres. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20110709/b8e4dd7c/attachment-0001.htm>
