Re: [petsc-users] Galerkin multigrid coarsening
On 30 January 2014 22:05, Jed Brown j...@jedbrown.org wrote: I did not have an opportunity to test what happens if I don't set any restriction, but I'm hoping it will then use P^T, as before. Yes, it will. Only setting the interpolation, and not the restriction, results in a crash for me (with output given at the bottom of this message). Looking at the changed code, is it not the case that if restrct is unset, the code will still try to use it in the MatMatMatMult() inside the else-part of the new code? If restrct is not set, it will surely differ from interpolate in the tests on lines 628 and 641, and therefore trigger the else-part of the if-else constructs, thereby causing this crash, right? I applied the changes to the master-branch, so I'm hoping that is not the reason for this problem. Here is the output I'm getting when only setting the interpolation: [0]PETSC ERROR: - Error Message [0]PETSC ERROR: Null argument, when expecting valid pointer! [0]PETSC ERROR: Null Object: Parameter # 1! [0]PETSC ERROR: [0]PETSC ERROR: Petsc Development GIT revision: v3.4.3-2428-g0a70bb0 GIT Date: 2014-01-30 13:56:44 -0600 [0]PETSC ERROR: See docs/changes/index.html for recent updates. [0]PETSC ERROR: See docs/faq.html for hints about trouble shooting. [0]PETSC ERROR: See docs/index.html for manual pages. [0]PETSC ERROR: [0]PETSC ERROR: ./timeevolution.exe on a arch-linux2-cxx-debug named enlil.uio.no by tmac Fri Jan 31 18:00:41 2014 [0]PETSC ERROR: Libraries linked from /mn/anatu/cma-u3/tmac/usr/stow/petsc_complex_debug_cpp/lib [0]PETSC ERROR: Configure run at Fri Jan 31 17:54:00 2014 [0]PETSC ERROR: Configure options --prefix=/mn/anatu/cma-u3/tmac/usr/stow/petsc_complex_debug_cpp --with-clanguage=C++ --with-scalar-type=complex --with-shared-libraries=1 --with-debugging=1 --with-superlu=1 --with-superlu-lib=/mn/anatu/cma-u3/tmac/usr/lib/libsuperlu.so --with-superlu-include=/mn/anatu/cma-u3/tmac/usr/include/superlu --with-ptscotch=1 --with-ptscotch-include=/mn/anatu/cma-u3/tmac/usr/include/scotch --with-ptscotch-lib=[/mn/anatu/cma-u3/tmac/usr/lib/libptscotch.so,/mn/anatu/cma-u3/tmac/usr/lib/libptscotcherr.so,/mn/anatu/cma-u3/tmac/usr/lib/libscotch.so,/mn/anatu/cma-u3/tmac/usr/lib/libscotcherr.so] --with-blas-lib=/mn/anatu/cma-u3/tmac/usr/lib/libsatlas.so --with-lapack-lib=/mn/anatu/cma-u3/tmac/usr/lib/libsatlas.so --with-fortran-interfaces=0 [0]PETSC ERROR: [0]PETSC ERROR: MatMatMatMult() line 9069 in /work/petsc/src/mat/interface/matrix.c [0]PETSC ERROR: PCSetUp_MG() line 631 in /work/petsc/src/ksp/pc/impls/mg/mg.c [0]PETSC ERROR: PCSetUp() line 888 in /work/petsc/src/ksp/pc/interface/precon.c [0]PETSC ERROR: KSPSetUp() line 278 in /work/petsc/src/ksp/ksp/interface/itfunc.c [0]PETSC ERROR: main() line 244 in /mn/anatu/cma-u3/tmac/research/sim/prog.cpp Setting both the interpolation and restriction works fine, as I mentioned in the earlier message. Best regards Torquil Sørensen
Re: [petsc-users] Galerkin multigrid coarsening
Torquil Macdonald Sørensen torq...@gmail.com writes: On 30 January 2014 22:05, Jed Brown j...@jedbrown.org wrote: I did not have an opportunity to test what happens if I don't set any restriction, but I'm hoping it will then use P^T, as before. Yes, it will. Only setting the interpolation, and not the restriction, results in a crash for me (with output given at the bottom of this message). Looking at the changed code, is it not the case that if restrct is unset, the code will still try to use it in the MatMatMatMult() inside the else-part of the new code? If restrct is not set, it will surely differ from interpolate in the tests on lines 628 and 641, and therefore trigger the else-part of the if-else constructs, thereby causing this crash, right? Sorry, this is my fault. (I thought restrct was configured before getting to this bit of code, but clearly not.) Fixed now. pgp1mS0E0xnYn.pgp Description: PGP signature
[petsc-users] Galerkin multigrid coarsening
Hi, While doing multigrid it is possible to explicitly set restriction and prolongation/interpolation operators in PETSC using PCMGSetRestriction and PCMGSetInterpolation. In many cases, the restriction (R) and prolongation (P) operators are simply the transpose of each other (R=P’). Yet, in certain cases, for example variable viscosity Stokes with a staggered finite difference discretization, it is advantageous if they are different (see http://arxiv.org/pdf/1308.4605.pdf). Accordding to the Wesseling textbook, Galerkin coarsening of the fine grid matrix is defined as: Acoarse = R*A*P Yet, as far as I can tell, PETSc seems to implement this as: Acoarse = R*A*R’ even in the case that R is different from P’. Is there a way for PETSc to use the actually provided prolongation and restriction operators to compute the coarse grid approximation? thanks! Boris ___ Boris J.P. Kaus Institute of Geosciences, Geocycles Research Center Center for Computational Sciences. University of Mainz, Mainz, Germany Office: 00-285 Tel:+49.6131.392.4527 http://www.geo-dynamics.eu ___
Re: [petsc-users] Galerkin multigrid coarsening
Boris Kaus k...@uni-mainz.de writes: While doing multigrid it is possible to explicitly set restriction and prolongation/interpolation operators in PETSC using PCMGSetRestriction and PCMGSetInterpolation. In many cases, the restriction (R) and prolongation (P) operators are simply the transpose of each other (R=P’). Yet, in certain cases, for example variable viscosity Stokes with a staggered finite difference discretization, it is advantageous if they are different (see http://arxiv.org/pdf/1308.4605.pdf). Accordding to the Wesseling textbook, Galerkin coarsening of the fine grid matrix is defined as: Acoarse = R*A*P Yet, as far as I can tell, PETSc seems to implement this as: Acoarse = R*A*R’ Certainly, the code just had an outdated assumption. I think I have added support for this (it does R*A*P when R!=P), but I don't have a test case readily available. Could you try branch 'jed/pcmg-galerkin-rap' (if you were using v3.4/maint) or 'next' if you've been tracking petsc-dev? pgpJYCCQqyXQs.pgp Description: PGP signature
Re: [petsc-users] Galerkin multigrid coarsening
Thanks Jed, I'll give it a try and let you know. Might take a bit though. Boris On Jan 30, 2014, at 17:45, Jed Brown j...@jedbrown.org wrote: Boris Kaus k...@uni-mainz.de writes: While doing multigrid it is possible to explicitly set restriction and prolongation/interpolation operators in PETSC using PCMGSetRestriction and PCMGSetInterpolation. In many cases, the restriction (R) and prolongation (P) operators are simply the transpose of each other (R=P’). Yet, in certain cases, for example variable viscosity Stokes with a staggered finite difference discretization, it is advantageous if they are different (see http://arxiv.org/pdf/1308.4605.pdf). Accordding to the Wesseling textbook, Galerkin coarsening of the fine grid matrix is defined as: Acoarse = R*A*P Yet, as far as I can tell, PETSc seems to implement this as: Acoarse = R*A*R’ Certainly, the code just had an outdated assumption. I think I have added support for this (it does R*A*P when R!=P), but I don't have a test case readily available. Could you try branch 'jed/pcmg-galerkin-rap' (if you were using v3.4/maint) or 'next' if you've been tracking petsc-dev?
Re: [petsc-users] Galerkin multigrid coarsening
On 30/01/14 17:45, Jed Brown wrote: Boris Kaus k...@uni-mainz.de writes: While doing multigrid it is possible to explicitly set restriction and prolongation/interpolation operators in PETSC using PCMGSetRestriction and PCMGSetInterpolation. In many cases, the restriction (R) and prolongation (P) operators are simply the transpose of each other (R=P’). Yet, in certain cases, for example variable viscosity Stokes with a staggered finite difference discretization, it is advantageous if they are different (see http://arxiv.org/pdf/1308.4605.pdf). Accordding to the Wesseling textbook, Galerkin coarsening of the fine grid matrix is defined as: Acoarse = R*A*P Yet, as far as I can tell, PETSc seems to implement this as: Acoarse = R*A*R’ Certainly, the code just had an outdated assumption. I think I have added support for this (it does R*A*P when R!=P), but I don't have a test case readily available. Could you try branch 'jed/pcmg-galerkin-rap' (if you were using v3.4/maint) or 'next' if you've been tracking petsc-dev? This question was similar to my recent unanswered one: http://lists.mcs.anl.gov/pipermail/petsc-users/2014-January/020382.html I just tried jed/pcmg-galerkin-rap, and it seems to work fineI verified that the coarse system matrix is R*A*P, for a two-level PCMG. I'm first calling PCMGSetInterpolation() with a matrix P, and then PCMGSetInterpolation() with a matrix R. Previously R was ignored, and I got A_c = P^T*A*P With jed/pcmg-galerkin-rap, I'm getting: A_c = R*A*P So now I can experiment with using R or P^T, which is very nice! I did not have an opportunity to test what happens if I don't set any restriction, but I'm hoping it will then use P^T, as before. Best regards Torquil Sørensen
Re: [petsc-users] Galerkin multigrid coarsening
Torquil Macdonald Sørensen torq...@gmail.com writes: This question was similar to my recent unanswered one: http://lists.mcs.anl.gov/pipermail/petsc-users/2014-January/020382.html That's why I Cc'd you. I just tried jed/pcmg-galerkin-rap, and it seems to work fineI verified that the coarse system matrix is R*A*P, for a two-level PCMG. I'm first calling PCMGSetInterpolation() with a matrix P, and then PCMGSetInterpolation() with a matrix R. Previously R was ignored, and I got A_c = P^T*A*P With jed/pcmg-galerkin-rap, I'm getting: A_c = R*A*P So now I can experiment with using R or P^T, which is very nice! Thanks for testing. I did not have an opportunity to test what happens if I don't set any restriction, but I'm hoping it will then use P^T, as before. Yes, it will. pgpE1H7plLNgn.pgp Description: PGP signature
Re: [petsc-users] Galerkin multigrid coarsening
On 30/01/14 22:05, Jed Brown wrote: Torquil Macdonald Sørensen torq...@gmail.com writes: This question was similar to my recent unanswered one: http://lists.mcs.anl.gov/pipermail/petsc-users/2014-January/020382.html That's why I Cc'd you. Thanks, I didn't notice that. I am actually very impressed with the helpfulness from the Petsc developers on this mailing list. - Torquil
