[petsc-users] Meaning of the order of PETSC_VIEWER_ASCII_INDEX format in PETSc

[Paula Sanematsu]

 I see. Thanks for the explanation.

Yes, that's the stage I'm in now. I am developing the code and only
testing+validating small samples, so I am trying to visualize the results
in Matlab. But in the future, Matlab will probably not be feasible so I
will probably need to use the binary format and visualize in Avizo.



On Wed, Feb 7, 2018 at 2:29 PM, Smith, Barry F. <bsmith at mcs.anl.gov> wrote:

>
>   Here is the code VecView_MPI_ASCII()
>
>         if (format == PETSC_VIEWER_ASCII_INDEX) {
>           ierr = PetscViewerASCIIPrintf(viewer,"%D:
> ",cnt++);CHKERRQ(ierr);
>         }
> #if defined(PETSC_USE_COMPLEX)
>         if (PetscImaginaryPart(xarray[i]) > 0.0) {
>           ierr = PetscViewerASCIIPrintf(viewer,"%g + %g
> i\n",(double)PetscRealPart(xarray[i]),(double)
> PetscImaginaryPart(xarray[i]));CHKERRQ(ierr);
>         } else if (PetscImaginaryPart(xarray[i]) < 0.0) {
>           ierr = PetscViewerASCIIPrintf(viewer,"%g - %g
> i\n",(double)PetscRealPart(xarray[i]),-(double)
> PetscImaginaryPart(xarray[i]));CHKERRQ(ierr);
>         } else {
>           ierr = PetscViewerASCIIPrintf(viewer,
> "%g\n",(double)PetscRealPart(xarray[i]));CHKERRQ(ierr);
>         }
> #else
>         ierr = PetscViewerASCIIPrintf(viewer,"%g\n",(double)xarray[i]);
> CHKERRQ(ierr);
> #endif
>       }
>       /* receive and print messages */
>       for (j=1; j<size; j++) {
>         ierr = MPI_Recv(values,(PetscMPIInt)len,MPIU_SCALAR,j,tag,
> PetscObjectComm((PetscObject)xin),&status);CHKERRQ(ierr);
>         ierr = MPI_Get_count(&status,MPIU_SCALAR,&n);CHKERRQ(ierr);
>         if (format != PETSC_VIEWER_ASCII_COMMON) {
>           ierr = PetscViewerASCIIPrintf(viewer,"Process
> [%d]\n",j);CHKERRQ(ierr);
>         }
>         for (i=0; i<n; i++) {
>           if (format == PETSC_VIEWER_ASCII_INDEX) {
>             ierr = PetscViewerASCIIPrintf(viewer,"%D:
> ",cnt++);CHKERRQ(ierr);
>           }
> #if defined(PETSC_USE_COMPLEX)
>           if (PetscImaginaryPart(values[i]) > 0.0) {
>             ierr = PetscViewerASCIIPrintf(viewer,"%g + %g
> i\n",(double)PetscRealPart(values[i]),(double)
> PetscImaginaryPart(values[i]));CHKERRQ(ierr);
>           } else if (PetscImaginaryPart(values[i]) < 0.0) {
>             ierr = PetscViewerASCIIPrintf(viewer,"%g - %g
> i\n",(double)PetscRealPart(values[i]),-(double)
> PetscImaginaryPart(values[i]));CHKERRQ(ierr);
>           } else {
>             ierr = PetscViewerASCIIPrintf(viewer,
> "%g\n",(double)PetscRealPart(values[i]));CHKERRQ(ierr);
>           }
> #else
>           ierr = PetscViewerASCIIPrintf(viewer,"%g\n",(double)values[i]);
> CHKERRQ(ierr);
> #endif
>         }
>       }
>
> So each process ships its values to process zero who prints them in order.
>
> Note that printing out vectors and matrices as ASCII is just for toys and
> to help debug. For large runs one should always use some variant of binary
> output.
>
>   Barry
>
>
> > On Feb 7, 2018, at 1:08 PM, Paula Sanematsu <paulasan at gmail.com> wrote:
> >
> > I am using PETSc 3.7.6 and Fortran.
> >
> > I am trying to output a PETSc vector that contains the solution of a
> linear system. I am using VecView with the PETSC_VIEWER_ASCII_INDEX format
> as follows:
> >
> > call PetscViewerASCIIOpen(PETSC_COMM_WORLD,"output.dat",viewer,ierr)
> > call PetscViewerPushFormat(viewer,PETSC_VIEWER_ASCII_INDEX,ierr)
> > call VecView(myVec,viewer,ierr)
> >
> > When I run with 4 processors, my output file looks like:
> >
> > Vec Object: 4 MPI processes
> >   type: mpi
> > Process [0]
> > 0: 30.7501
> > 1: 164.001
> > 2: 41.0001
> > 3: 164.001
> > .
> > .
> > .
> > Process [1]
> > 4988: 60.1443
> > 4989: 157.257
> > 4990: 271.518
> > 4991: 366.669
> > .
> > .
> > .
> > Process [2]
> > 9977: 114.948
> > 9978: -77.2896
> > 9979: 823.142
> > 9980: -1096.19
> > .
> > .
> > .
> > Process [3]
> > 14916: 0.
> > 14917: 4.4056
> > 14918: 2.08151
> > 14919: -0.110862
> > .
> > .
> > .
> > 19843: 0.
> >
> > My question is: each processor outputs the part of the vector that it
> owns? Or does PETSc collects each processor's parts and then processor 0
> sequentially outputs the 1st quarter of the global vector, processor 1
> outputs the 2nd quarter of the global vector, processor 2 outputs the 3rd
> quarter of the global vector, and so on? Or, does PETSc do something else?
> >
> > Thank you!
> >
> > Paula
> >
>
>
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