On Mar 21, 2008, at 8:03 AM, Nicolas Tardieu wrote: > Dear Barry, > > I have a few questions about inodes : > - can the user specify the inodes sizes (it seems to me this is an > automatic PETSc feature to gain performance, right?)?
No, they must be inodes, they are not arbitary > > - can the inodes have different sizes? Yes, they are what ever they are. > > > Otherwise I plan to define a new matrix type MATSEQVBAIJ (VB for > variable block) based on MATSEQAIJ with an additional attribute > defining the block sizes. This is overkill, you will end up doing a lot more work then you need to! The locations for storing the diagonal blocks is already in the MATSEQAIJ data structures, if you write code to replace the MatRelax_Inode (that uses that same diagonal space) you are done. Barry > > > Thanks, > > Nicolas > > 2008/3/20, Barry Smith <bsmith at mcs.anl.gov>: > DON"T USE GREP! Use etags > # To access the tags in EMACS, type M-x visit-tags-table and specify > # the file petsc/TAGS. > # 1) To move to where a PETSc function is defined, enter M-. and the > # function name. > # 2) To search for a string and move to the first occurrence, > # use M-x tags-search and the string. > # To locate later occurrences, use M-, > > It may not be in petsc-2.3.3 you may need to use petsc-dev > http://www-unix.mcs.anl.gov/petsc/petsc-as/developers/index.html > > it is in src/mat/impls/aij/seq/inode.c > > > > Barry > > > > On Mar 20, 2008, at 1:52 PM, Nicolas Tardieu wrote: > > > Dear Barry, > > > > Thank you very much for your quick answer. > > I am searching for MatRelax_Inode in PETSc src directory using grep. > > But I just can't find it! Please note I am using 2.3.3p6 > > Could you please tell me where this routine is? > > > > Nicoals > > > > 2008/3/20, Barry Smith <bsmith at mcs.anl.gov>: > > Nicolas, > > > > Actually we are very close to this. Check out the routine > > MatRelax_Inode() which is for AIJ matrices. > > For the block size it uses the inode size. If your matrix has inodes > > that match the blocks you want > > then everything is there already just use the PCSOR. > > > > If you do not have inodes then you can mimic the > MatRelax_Inode() > > code to make a new > > routine MatPBRelax_SeqAIJ(). If you do implement this we'd love to > add > > it to PETSc. > > > > > > Please let us know if you have additional questions. > > > > > > Barry > > > > > > > > > > On Mar 20, 2008, at 1:07 PM, Nicolas Tardieu wrote: > > > > > Dear PETSc experts, > > > > > > I am currently designing a multigrid PC that needs to operate on > > > variable block size matrices. I know PETSc does not support this > > > feature. > > > So, I will do it "by hand". Neverthless I would like to be able > to > > > use some smoothers like Jacobi or SOR in their block version. > > > > > > What is the best solution that would work both in sequential and > > > parallel? > > > > > > - define some MATSHELL that handle variable block size > > > -> will I be able to use in some way a block Jacobi or SOR? > > > -> would it be possible to use CSR inside the MATSHELL and > > > manage the variable blocks. > > > > > > - use a AIJ matrix and manage the blocks using some indirection > > > mechanism and reprogram Jacobi or SOR > > > > > > > > > > > > Thank you, > > > > > > Nicolas > > > > > > > > >