Hi Matt, Sorry to distribute you again. I still have trouble with KSPComputeExplicitOperator. I reduced the matrix size to around 1000*1000. The time-cost of this function is acceptable, but when I output the preconditioned matrix, all the values are equal to zero! Here is part of my codes, do I operate error with this function?
PC pc; KSP ksp; Mat A,PA; Vec b,x; ierr=KSPCreate(PETSC_COMM_WORLD,&ksp);CHKERRQ(ierr); ierr=KSPSetOperators(ksp,A,A);CHKERRQ(ierr); ierr=KSPGetPC(ksp,&pc);CHKERRQ(ierr); ierr=PCSetType(pc,PCHYPRE);CHKERRQ(ierr); ierr=KSPSetType(ksp,KSPGMRES);CHKERRQ(ierr); ierr=KSPSetFromOptions(ksp);CHKERRQ(ierr); ierr=KSPSolve(ksp,b,x);CHKERRQ(ierr); ierr=KSPComputeExplicitOperator(ksp,&PA); ierr=MatAssemblyBegin(PA,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr); ierr=MatAssemblyEnd(PA,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr); ierr=MatView(PA,viewer);CHKERRQ(ierr); Thank you very much! Daye At 2018-03-23 07:41:26, "Matthew Knepley" <[email protected]> wrote: On Thu, Mar 22, 2018 at 8:29 PM, 我 <[email protected]> wrote: Hi all, I want to analyze the preconditioned matrix. But the KSPComputeExplicitOperator costs too much time to obtain the matrix. My origin matrix is about 3000*3000 sparse one. I noticed this function is applicable for the relative small system. What's the matrix-size limitation for this function? And for my case, any suggestions to solve it with less time? This is just a really expensive operation. There is no way around it. Matt Thank you very much! daye -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener https://www.cse.buffalo.edu/~knepley/
