[petsc-users] teething troubles / MatView() fails silently for transposed seqaij matrix

[Junchao Zhang]

Looks like MatCreateTranspose does not form the transpose, See the notes
here
<http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatCreateTranspose.html>.
You
may want to use MatTranspose
<http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatTranspose.html>
.

--Junchao Zhang

On Fri, Apr 13, 2018 at 7:25 AM, Bryan Jurish <moocow.bovine at gmail.com>
wrote:

> morning all,
>
> Apologies for what is very probably a boundlessly stupid question.  I've
> just begun exploring PETSc, but find myself stumped by a pretty trivial
> task.  I would like to load a real binary seqaij matrix and save its
> transposition (also as a binary  seqaij matrix) to a different file.
> I've tried PETSc v3.7.5 on debian stretch and v3.6.2 on ubuntu 16.04, both
> with no joy.  In both cases the program runs to completion and exits
> normally, but no output file ("INFILE.T") is written.  Stepping through
> MatView() with the debugger, it seems that (mat->ops->view) is not set for
> the transposition I created with MatCreateTranspose(). I suppose I could
> always loop over the input indices and assemble a physical transposition
> manually, but that rather defeats the purpose of the exercise... can anyone
> here tell me what I'm doing wrong (almost certainly something fundamental
> and obvious)?  Thanks in advance for any help you can provide.
>
> marmosets,
>   Bryan
>
> ::: BEGIN MINIMUM BROKEN EXAMPLE :::
> /*-*- Mode: C -*-*/
>
> static char help[] = "Transposes a matrix in BINARY format\n\
> Input parameters are:\n\
>   -file INFILE     : input matrix in binary format\n\
>   -out OUTFILE     : write output to OUTFILE (default=INFILE.T)\n\
> ";
>
>
> #include <petscmat.h>
>
> //-- handle v3.7 API change
> #if PETSC_VERSION_MAJOR>3 || (PETSC_VERSION_MAJOR==3 &&
> PETSC_VERSION_MINOR>=7)
>   #define OPTIONS_NULL NULL,NULL
> #else
>   #define OPTIONS_NULL NULL
> #endif
>
>
> #undef __FUNCT__
> #define __FUNCT__ "main"
> int main(int argc,char **args)
> {
>   Mat            A,B;
>   char           infile[PETSC_MAX_PATH_LEN], outfile[PETSC_MAX_PATH_LEN];
>   PetscErrorCode ierr;
>   PetscInt       m,n;
>   PetscViewer    view;
>   PetscBool      flg_file,flg_out;
>   PetscMPIInt    size;
>
>   PetscInitialize(&argc,&args,(char*)0,help);
>   ierr = MPI_Comm_size(PETSC_COMM_WORLD,&size);CHKERRQ(ierr);
>   ierr = PetscPrintf(PETSC_COMM_WORLD," MPI_Comm_size reports %d
> process(es) available.\n", size);CHKERRQ(ierr);
>   if (size != 1) SETERRQ(PETSC_COMM_WORLD,PETSC_ERR_SUP,"This is a
> uniprocessor operation only!");
>
>   /*-- Read in source matrix, binary --*/
>   ierr = PetscOptionsGetString(OPTIONS_NULL,"-file",infile,PETSC_MAX_
> PATH_LEN,&flg_file);CHKERRQ(ierr);
>   if (!flg_file) SETERRQ(PETSC_COMM_WORLD,1,"Must specify a file name
> with the -file option");
>
> #if defined(PETSC_USE_COMPLEX)
>   ierr = PetscPrintf(PETSC_COMM_WORLD," Reading COMPLEX matrix from binary
> file `%s'...\n", infile);CHKERRQ(ierr);
> #else
>   ierr = PetscPrintf(PETSC_COMM_WORLD," Reading REAL matrix from binary
> file `%s'...\n", infile);CHKERRQ(ierr);
> #endif
>   ierr = PetscViewerBinaryOpen(PETSC_COMM_WORLD,infile,FILE_MODE_
> READ,&view);CHKERRQ(ierr);
>   ierr = MatCreate(PETSC_COMM_WORLD,&A);CHKERRQ(ierr);
>   ierr = MatSetFromOptions(A);CHKERRQ(ierr);
>   ierr = MatLoad(A,view);CHKERRQ(ierr);
>   ierr = PetscViewerDestroy(&view);CHKERRQ(ierr);
>   //
>   ierr = MatGetSize(A,&m,&n);
>   ierr = PetscPrintf(PETSC_COMM_WORLD," Read input matrix of size
> (m=%D,n=%D)\n", m,n);CHKERRQ(ierr);
>
>   /*-- guts: transpose --*/
>   ierr = PetscPrintf(PETSC_COMM_WORLD," Performing transposition
> (constructive)\n");CHKERRQ(ierr);
>   ierr = MatCreateTranspose(A,&B);CHKERRQ(ierr);
>
>   /*-- dump transposed matrix --*/
>   ierr = PetscOptionsGetString(OPTIONS_NULL,"-out",outfile,PETSC_MAX_
> PATH_LEN,&flg_out);CHKERRQ(ierr);
>   if (!flg_out) {
>     strcpy(outfile,infile);
>     strcat(outfile,".T");
>   }
>   ierr = PetscPrintf(PETSC_COMM_SELF," Writing transposed matrix in binary
> format to '%s' ...\n", outfile);CHKERRQ(ierr);
>   ierr = PetscViewerBinaryOpen(PETSC_COMM_SELF,outfile,FILE_MODE_
> WRITE,&view);CHKERRQ(ierr);
>   ierr = MatView(B,view);CHKERRQ(ierr);
>
>   /* !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
>    * output file is not written: much wailing and gnashing of teeth
>    * !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
>    */
>
>   /*-- cleanup --*/
>   ierr = MatDestroy(&A);CHKERRQ(ierr);
>   ierr = MatDestroy(&B);CHKERRQ(ierr);
>   ierr = PetscViewerDestroy(&view);CHKERRQ(ierr);
>   ierr = PetscFinalize();
>   return 0;
> }
> ::: END MINIMUM BROKEN EXAMPLE :::
>
> --
> Bryan Jurish                           "There is *always* one more bug."
> moocow.bovine at gmail.com         -Lubarsky's Law of Cybernetic Entomology
>
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