On Mon, Jun 20, 2011 at 11:16 PM, Mohammad Mirzadeh <mirzadeh at gmail.com>wrote:
> Matt, > > I see. Please forgive my ignorance, but I don't quite understand why you > should not be able to set a tolerance for it. Could you please point me to > the source file that applies the MAT_IGNORE_ZERO_ENTRIES option to the > matrix? I may be able to manually modify it. > src/mat/impls/aij/seq/aij.c. Search for ignorezeroentries. I think changing it here would be bad design. Its simple to process your input matrix to MatSetValues() to chop small values to 0.0 Matt > Thanks, > Mohammad > > > On Mon, Jun 20, 2011 at 2:34 PM, Matthew Knepley <knepley at gmail.com>wrote: > >> On Mon, Jun 20, 2011 at 9:31 PM, Mohammad Mirzadeh <mirzadeh at >> gmail.com>wrote: >> >>> Thanks John -- taht's helpful. Do you also know how I can change the >>> tolerance for dropping elements? >>> >> >> Right now, this only discards entires which are exactly floating point >> 0.0. >> >> Matt >> >> >>> Mohammad >>> >>> On Mon, Jun 20, 2011 at 1:12 PM, John Mousel <john.mousel at >>> gmail.com>wrote: >>> >>>> See the matrix options available in the man pages. I think the function >>>> below is what you are looking for. >>>> >>>> >>>> http://www.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/docs/manualpages/Mat/MatSetOption.html >>>> >>>> >>>> MatSetOption >>>> <http://www.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/docs/manualpages/Mat/MatSetOption.html#MatSetOption>(A,MAT_IGNORE_ZERO_ENTRIES,PETSC_TRUE >>>> >>>> <http://www.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/docs/manualpages/Sys/PETSC_TRUE.html#PETSC_TRUE>); >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> Best Regards, >>>> John >>>> >>>> >>>> >>>> >>>> On Mon, Jun 20, 2011 at 2:42 PM, Mohammad Mirzadeh <mirzadeh at >>>> gmail.com>wrote: >>>> >>>>> Hi folks, >>>>> >>>>> I've noticed that MatSetValues explicitly inserts zeros in the matrix >>>>> if an element is really zero. Is there a way to drop elements (or not save >>>>> them in the first place) that are below a certain tolerance? I realize one >>>>> way of doing it is in the application code and when using MatSetValues but >>>>> I'm just wondering if PETSc has a function for it? >>>>> >>>>> Thanks, >>>>> Mohammad >>>>> >>>> >>>> >>> >> >> >> -- >> 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 >> > > -- 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 -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20110620/0f2323c1/attachment.htm>
