On Sun, Jul 12, 2009 at 5:41 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
> > The manual page for MatLoad() and VecLoad() contain the definitions of > those structs. This pointer is great. > > The file binary format is independent of parallel storage of the matrix > so has no information about the "diagonal" and "off-diagonal" parts of the > matrix. That is all determined when the binary file is read in. That's exactly what I get confused with. Thank you very much, Yan > > Barry > > > > On Jul 12, 2009, at 3:30 PM, Ryan Yan wrote: > > >> http://www.mcs.anl.gov/petsc/petsc-2/snapshots/petsc-current/src/mat/examples/tutorials/ex5.c.html >> >> Hi All, >> I am tring to read through an example about PetscBinaryRead. It looks like >> the matrix is reading from a CRS matrix object descriptor "fd1, or fd2". >> >> I have difficulty of understand the line 50: >> +++++++++++++++++++++++++++++ >> 50: PetscBinaryRead(fd2,(char *)header,4,PETSC_INT); >> +++++++++++++++++++++++++++++ >> From the context, my guess is: >> header[0] unknown >> >> header[1] contains the info of how many rows of matrix stored on this >> processor >> >> header[2] contains the info of how many global columns of the matrix >> >> header[3] unknown >> >> and line: >> ++++++++++++++++++++++++++++ >> 86: PetscBinaryRead(fd1,ourlens,m,PETSC_INT); >> 101: PetscBinaryRead(fd1,mycols,ourlens[i],PETSC_INT); >> +++++++++++++++++++++++++++++++ >> From the context, my guess is: >> ourlens[i] stores the length of the ith local row for the "local" portion >> of the matrix. >> >> mycols is an array storing the column indices of the nonzero entries of >> the ith local row for the "local" portion of the matrix(include diagonal and >> off diagonal). >> >> >> >> >> >> Is there any pointer to the definition of the struct descriptor. >> >> Can anyone confirm my guess and provide a pointer or example? How does >> the PetscBinaryRead() switch smoothly between reading different informations >> with the same parameter list. >> >> Thank you very much, >> >> Yan >> >> > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20090712/85772825/attachment.htm>
