what's the difference between PetscViewerASCIIOpen() and PetscViewerBinaryOpen()?

[Barry Smith]

    The files should be the same.

    Barry

1) If the matrix is generated differently in parallel then sequential  
then rounding of the floating point
operations will result in very slightly different numerical values in  
the matrix.

2) If the ordering of the the unknowns is different in the parallel  
and sequential then the matrices
will, of course, be permutations of each other.


On Feb 12, 2008, at 1:06 PM, Yujie wrote:

> hi, Matt
>
> If I output matrix with binary format, should the file format  
> obtained from sequential output is the same with that from parallel  
> output? I mean that I don't need to consider whether  
> MatView_***_Binary() is parallel or sequential when I use the matrix  
> file.
>
> thanks a lot.
>
> Regards,
> Yujie
>
> On 1/23/08, Matthew Knepley <knepley at gmail.com> wrote:
> On Jan 23, 2008 2:18 PM, Yujie <recrusader at gmail.com> wrote:
> > Thank you for your further explanation. I just want to use this  
> data in
> > other packages. I think that ASCII file is likely better. Because  
> I don't
> > know the format of the binary file? how to find it?
>
> Look at MatView_SeqAIJ_Binary() in src/mat/impls/aij/seq/aij.c. The
> format is pretty simple.
>
> > In addition, do you have any better methods to save the sparsity  
> structure
> > picture of the matrix? Now, I use "-mat_view_draw" to do this.  
> However, the
> > speed is very slow and the picture is small. I want to get a big  
> picture and
> > directly save it to the disk?
> >  could you give me some advice? thanks a lot.
>
> We do not have a better way to make the sparsity picture. I assume  
> you could
> write something that decides how many pixels to use, calculates an  
> average
> occupancy per pixel, and writes a BMP or something.
>
>   Matt
>
> > Regards,
> > Yujie
> >
> > On 1/23/08, Matthew Knepley <knepley at gmail.com > wrote:
> > > On Jan 22, 2008 11:01 PM, Yujie <recrusader at gmail.com> wrote:
> > > > Dear Matt:
> > > >
> > > > thank you for your reply. Do you have any method to generate  
> an ascii
> > file
> > > > of the huge sparse matrix? thanks
> > >
> > > I think you miss my point. The PETSc function is not a bad way  
> to generate
> > > ASCII matrices. ASCII matrices make "no sense" for large  
> operators.
> > >
> > >    Matt
> > >
> > > > Regards,
> > > > Yujie
> > > >
> > > >
> > > >
> > > > On 1/23/08, Matthew Knepley <knepley at gmail.com> wrote:
> > > > > On Jan 22, 2008 8:50 PM, Yujie < recrusader at gmail.com> wrote:
> > > > > > Hi everyone:
> > > > > >
> > > > > > #include "petsc.h"
> > > > > >  PetscErrorCode PetscViewerASCIIOpen(MPI_Comm comm,const  
> char
> > > > > > name[],PetscViewer *lab)
> > > > > >
> > > > > > #include "petsc.h"
> > > > > >  PetscErrorCode PetscViewerBinaryOpen(MPI_Comm comm,const  
> char
> > > > > > name[],PetscFileMode type,PetscViewer *binv)
> > > > > >
> > > > > > if the difference between them is that one for ASCII  
> output and the
> > > > other
> > > > > > for Binary output, why are there different parameters?
> > > > >
> > > > > It is historical. If you want to be generic, you should use
> > > > >
> > > > >   PetscViewerCreate()
> > > > >   PetscViewerSetType()
> > > > >   PetscViewerFileSetMode()
> > > > >   PetscViewerFileSetName()
> > > > >
> > > > > which can create both.
> > > > >
> > > > > > The speed to output matrix is very fast when I use
> > > > PetscViewerBinaryOpen.
> > > > > > However, when I use PetscViewerASCIIOpen, I can't get the  
> matrix
> > output.
> > > > the
> > > > > > code always is running and it has taken about one day!  
> what's the
> > > > problem?
> > > > > > thank you.
> > > > >
> > > > > ASCII files do not make sense for large matrices. You should  
> use
> > binary
> > > > files.
> > > > >
> > > > >    Matt
> > > > >
> > > > > > Regards,
> > > > > > Yujie
> > > > > >
> > > > > >
> > > > > >
> > > > >
> > > > >
> > > > >
> > > > > --
> > > > > 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
> > >
> > >
> >
> >
>
>
>
> --
> 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
>
>

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