On Thu, Jan 24, 2013 at 1:29 PM, Peter Zajac <[email protected]> wrote: > Hi Roy, > > after constraining the matrices I get the correct eigenvalues and > wavefunctions -- thank you for helping me solve the problem. > > There is one last thing I wanted to ask. When I run the code now (with the > constrains), despite obtaining the correct results I get the following > error message: > > [0]PETSC ERROR: --------------------- Error Message > ------------------------------------ > [0]PETSC ERROR: Detected zero pivot in LU factorization: > see http://www.mcs.anl.gov/petsc/documentation/faq.html#ZeroPivot! > [0]PETSC ERROR: Empty row in matrix: row in original ordering 1223 in > permuted ordering 20! > [0]PETSC ERROR: > ------------------------------------------------------------------------ > [0]PETSC ERROR: Petsc Release Version 3.3.0, Patch 3, Wed Aug 29 11:26:24 > CDT 2012 > [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: ./femvib on a arch-linu named peter-VirtualBox by peter Thu > Jan 24 09:25:57 2013 > [0]PETSC ERROR: Libraries linked from > /home/peter/petsc-3.3-p3/arch-linux2-c-debug/lib > [0]PETSC ERROR: Configure run at Fri Nov 23 19:14:06 2012 > [0]PETSC ERROR: Configure options --download-f2cblaslapack=1 > [0]PETSC ERROR: > ------------------------------------------------------------------------ > [0]PETSC ERROR: MatLUFactorSymbolic_SeqAIJ() line 334 in > src/mat/impls/aij/seq/aijfact.c > [0]PETSC ERROR: MatLUFactorSymbolic() line 2750 in > src/mat/interface/matrix.c > [0]PETSC ERROR: PCSetUp_LU() line 135 in src/ksp/pc/impls/factor/lu/lu.c > [0]PETSC ERROR: PCSetUp() line 832 in src/ksp/pc/interface/precon.c > [0]PETSC ERROR: KSPSetUp() line 278 in src/ksp/ksp/interface/itfunc.c > [0]PETSC ERROR: PCSetUp_Redundant() line 176 in > src/ksp/pc/impls/redundant/redundant.c > [0]PETSC ERROR: PCSetUp() line 832 in src/ksp/pc/interface/precon.c > [0]PETSC ERROR: KSPSetUp() line 278 in src/ksp/ksp/interface/itfunc.c > [0]PETSC ERROR: STSetUp_Shift() line 94 in src/st/impls/shift/shift.c > [0]PETSC ERROR: STSetUp() line 280 in src/st/interface/stsolve.c > [0]PETSC ERROR: EPSSetUp() line 204 in src/eps/interface/setup.c > [0]PETSC ERROR: EPSSolve() line 109 in src/eps/interface/solve.c > [0]PETSC ERROR: SlepcAbs() line 486 in > "unknowndirectory/"src/solvers/slepc_eigen_solver.C > application called MPI_Abort(comm=0x84000000, 71) - process 0 > > According to the PETSC documentation zero pivot does not always mean the > matrix is singular and since I am getting the correct results I am ignoring > the error. Could my ignorance in this case cause a serious problem in the > future I should be aware of?
This is a real problem: > Empty row in matrix: row in original ordering 1223 in permuted ordering 20! I would definitely investigate the issue. Start by finding out which row is zero (i.e. what dof it corresponds to) and go from there. If worse comes to worst, make the problem small enough that you can print out and compute the SVD of the system matrix in Matlab or Gnuplot. That will tell you if there really is a zero eigenvalue in the matrix you are trying to solve, and the associated singular vector may tell you what this mode is. Although I don't think that's necessary this time. -- John ------------------------------------------------------------------------------ Master Visual Studio, SharePoint, SQL, ASP.NET, C# 2012, HTML5, CSS, MVC, Windows 8 Apps, JavaScript and much more. Keep your skills current with LearnDevNow - 3,200 step-by-step video tutorials by Microsoft MVPs and experts. ON SALE this month only -- learn more at: http://p.sf.net/sfu/learnnow-d2d _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
