[petsc-dev] How do I collect all the values from a sequential vector on the zeroth processor into a parallel PETSc vector ?
Franck Houssen
franck.houssen at inria.fr
Thu Jan 4 02:31:05 CST 2018
I attached it in the very first mail.
Franck
>> more vecScatterGatherRoot.cpp
// How do I collect all the values from a sequential vector on the zeroth processor into a parallel PETSc vector ?
//
// ~> g++ -o vecScatterGatherRoot.exe vecScatterGatherRoot.cpp -lpetsc -lm; mpirun -n X vecScatterGatherRoot.exe
#include "petsc.h"
int main(int argc,char **argv) {
PetscInitialize(&argc, &argv, NULL, NULL);
int size = 0; MPI_Comm_size(MPI_COMM_WORLD, &size);
int rank = 0; MPI_Comm_rank(MPI_COMM_WORLD, &rank);
PetscInt globSize = size;
Vec globVec; VecCreateMPI(PETSC_COMM_WORLD, 1, globSize, &globVec);
VecSetValue(globVec, rank, (PetscScalar) (1.+rank), INSERT_VALUES);
VecAssemblyBegin(globVec); VecAssemblyEnd(globVec);
VecView(globVec, PETSC_VIEWER_STDOUT_WORLD); PetscViewerFlush(PETSC_VIEWER_STDOUT_WORLD);
// Collect all the values from a parallel PETSc vector into a vector on the zeroth processor.
Vec locVec = NULL;
if (rank == 0) {
PetscInt locSize = globSize;
VecCreateSeq(PETSC_COMM_SELF, locSize, &locVec); VecSet(locVec, -1.);
}
VecScatter scatCtx; VecScatterCreateToZero(globVec, &scatCtx, &locVec);
VecScatterBegin(scatCtx, globVec, locVec, INSERT_VALUES, SCATTER_FORWARD);
VecScatterEnd (scatCtx, globVec, locVec, INSERT_VALUES, SCATTER_FORWARD);
// Modify sequential vector on the zeroth processor.
if (rank == 0) {
VecView(locVec, PETSC_VIEWER_STDOUT_SELF); PetscViewerFlush(PETSC_VIEWER_STDOUT_SELF);
VecScale(locVec, -1.);
VecView(locVec, PETSC_VIEWER_STDOUT_SELF); PetscViewerFlush(PETSC_VIEWER_STDOUT_SELF);
}
MPI_Barrier(MPI_COMM_WORLD);
// How do I collect all the values from a sequential vector on the zeroth processor into a parallel PETSc vector ?
VecSet(globVec, 0.);
VecScatterBegin(scatCtx, locVec, globVec, ADD_VALUES, SCATTER_REVERSE);
VecScatterEnd (scatCtx, locVec, globVec, ADD_VALUES, SCATTER_REVERSE);
VecView(globVec, PETSC_VIEWER_STDOUT_WORLD); PetscViewerFlush(PETSC_VIEWER_STDOUT_WORLD);
PetscFinalize();
}
----- Mail original -----
> De: "Barry F. Smith" <bsmith at mcs.anl.gov>
> À: "Franck Houssen" <franck.houssen at inria.fr>
> Cc: "Barry F. Smith" <bsmith at mcs.anl.gov>, "Matthew Knepley" <knepley at gmail.com>, "For users of the development
> version of PETSc" <petsc-dev at mcs.anl.gov>
> Envoyé: Mercredi 3 Janvier 2018 18:20:21
> Objet: Re: [petsc-dev] How do I collect all the values from a sequential vector on the zeroth processor into a
> parallel PETSc vector ?
>
>
> Send the complete code as an attachment.
>
>
> > On Jan 3, 2018, at 11:08 AM, Franck Houssen <franck.houssen at inria.fr>
> > wrote:
> >
> > ----- Mail original -----
> >> De: "Barry F. Smith" <bsmith at mcs.anl.gov>
> >> À: "Franck Houssen" <franck.houssen at inria.fr>
> >> Cc: "Matthew Knepley" <knepley at gmail.com>, "For users of the development
> >> version of PETSc" <petsc-dev at mcs.anl.gov>
> >> Envoyé: Mercredi 3 Janvier 2018 18:01:35
> >> Objet: Re: [petsc-dev] How do I collect all the values from a sequential
> >> vector on the zeroth processor into a
> >> parallel PETSc vector ?
> >>
> >>
> >>
> >>> On Jan 3, 2018, at 10:59 AM, Franck Houssen <franck.houssen at inria.fr>
> >>> wrote:
> >>>
> >>> I need the exact opposite operation of an entry in the FAQ called "How do
> >>> I
> >>> collect all the values from a parallel PETSc vector into a vector on the
> >>> zeroth processor?"
> >>
> >> You can use VecScatterCreateToZero() then do the scatter with scatter
> >> reverse.
> >>
> >
> > That's what I tried but got an error. Did I miss something ?
> >
> >>> tail vecScatterGatherRoot.cpp
> >
> > // How do I collect all the values from a sequential vector on the zeroth
> > processor into a parallel PETSc vector ?
> >
> > VecSet(globVec, 0.);
> > VecScatterBegin(scatCtx, locVec, globVec, ADD_VALUES, SCATTER_REVERSE);
> > VecScatterEnd (scatCtx, locVec, globVec, ADD_VALUES, SCATTER_REVERSE);
> > VecView(globVec, PETSC_VIEWER_STDOUT_WORLD);
> > PetscViewerFlush(PETSC_VIEWER_STDOUT_WORLD);
> >
> > PetscFinalize();
> > }
> >
> >>> mpirun -n 2 ./vecScatterGatherRoot.exe
> > Vec Object: 2 MPI processes
> > type: mpi
> > Process [0]
> > 1.
> > Process [1]
> > 2.
> > Vec Object: 1 MPI processes
> > type: seq
> > 1.
> > 2.
> > Vec Object: 1 MPI processes
> > type: seq
> > -1.
> > -2.
> > ...
> > [1]PETSC ERROR: [1] VecScatterBegin_MPI_ToOne line 161
> > /home/fghoussen/Documents/INRIA/petsc/src/vec/vec/utils/vscat.c
> > [1]PETSC ERROR: [1] VecScatterBegin line 1698
> > /home/fghoussen/Documents/INRIA/petsc/src/vec/vec/utils/vscat.c
> > [1]PETSC ERROR: --------------------- Error Message
> > --------------------------------------------------------------
> > [1]PETSC ERROR: Signal received
> > [1]PETSC ERROR: See http://www.mcs.anl.gov/petsc/documentation/faq.html for
> > trouble shooting.
> >
> >
> >>>
> >>> Shall I use VecScatterCreateToZero "backward", or, use VecScatterCreate
> >>> instead ? If yes, how ? (my understanding is that VecScatterCreate can
> >>> take only parallel vector as input)
> >>
> >> This understanding is completely incorrect.
> >>
> >> Barry
> >>
> >>
> >>> Not sure how to do this.
> >>>
> >>> Its not clear what you want. Do you want a seq vector duplicated on all
> >>> procs?
> >>>
> >>> No. The seq vec should "live" only on the master proc. This seq master
> >>> vec
> >>> should be "converted" into a parallel vector. Not sure how to do that
> >>>
> >>> Do you want it split up? The short
> >>> answer is, use the appropriate scatter.
> >>>
> >>> Matt
> >>>
> >>> Franck
> >>>
> >>> In this example, the final VecView of the parallel globVec vector should
> >>> be
> >>> [-1., -2.]
> >>>
> >>>>> mpirun -n 2 ./vecScatterGatherRoot.exe
> >>> Vec Object: 2 MPI processes
> >>> type: mpi
> >>> Process [0]
> >>> 1.
> >>> Process [1]
> >>> 2.
> >>> Vec Object: 1 MPI processes
> >>> type: seq
> >>> 1.
> >>> 2.
> >>> Vec Object: 1 MPI processes
> >>> type: seq
> >>> -1.
> >>> -2.
> >>> [1]PETSC ERROR:
> >>> ------------------------------------------------------------------------
> >>> [1]PETSC ERROR: Caught signal number 11 SEGV: Segmentation Violation,
> >>> probably memory access out of range
> >>>
> >>>>> more vecScatterGatherRoot.cpp
> >>> // How do I collect all the values from a sequential vector on the zeroth
> >>> processor into a parallel PETSc vector ?
> >>> //
> >>> // ~> g++ -o vecScatterGatherRoot.exe vecScatterGatherRoot.cpp -lpetsc
> >>> -lm;
> >>> mpirun -n X vecScatterGatherRoot.exe
> >>>
> >>> #include "petsc.h"
> >>>
> >>> int main(int argc,char **argv) {
> >>> PetscInitialize(&argc, &argv, NULL, NULL);
> >>> int size = 0; MPI_Comm_size(MPI_COMM_WORLD, &size);
> >>> int rank = 0; MPI_Comm_rank(MPI_COMM_WORLD, &rank);
> >>>
> >>> PetscInt globSize = size;
> >>> Vec globVec; VecCreateMPI(PETSC_COMM_WORLD, 1, globSize, &globVec);
> >>> VecSetValue(globVec, rank, (PetscScalar) (1.+rank), INSERT_VALUES);
> >>> VecAssemblyBegin(globVec); VecAssemblyEnd(globVec);
> >>> VecView(globVec, PETSC_VIEWER_STDOUT_WORLD);
> >>> PetscViewerFlush(PETSC_VIEWER_STDOUT_WORLD);
> >>>
> >>> // Collect all the values from a parallel PETSc vector into a vector on
> >>> the zeroth processor.
> >>>
> >>> Vec locVec = NULL;
> >>> if (rank == 0) {
> >>> PetscInt locSize = globSize;
> >>> VecCreateSeq(PETSC_COMM_SELF, locSize, &locVec); VecSet(locVec, -1.);
> >>> }
> >>> VecScatter scatCtx; VecScatterCreateToZero(globVec, &scatCtx, &locVec);
> >>> VecScatterBegin(scatCtx, globVec, locVec, INSERT_VALUES,
> >>> SCATTER_FORWARD);
> >>> VecScatterEnd (scatCtx, globVec, locVec, INSERT_VALUES,
> >>> SCATTER_FORWARD);
> >>>
> >>> // Modify sequential vector on the zeroth processor.
> >>>
> >>> if (rank == 0) {
> >>> VecView(locVec, PETSC_VIEWER_STDOUT_SELF);
> >>> PetscViewerFlush(PETSC_VIEWER_STDOUT_SELF);
> >>> VecScale(locVec, -1.);
> >>> VecView(locVec, PETSC_VIEWER_STDOUT_SELF);
> >>> PetscViewerFlush(PETSC_VIEWER_STDOUT_SELF);
> >>> }
> >>> MPI_Barrier(MPI_COMM_WORLD);
> >>>
> >>> // How do I collect all the values from a sequential vector on the
> >>> zeroth
> >>> processor into a parallel PETSc vector ?
> >>>
> >>> VecSet(globVec, 0.);
> >>> VecScatterBegin(scatCtx, locVec, globVec, ADD_VALUES, SCATTER_REVERSE);
> >>> VecScatterEnd (scatCtx, locVec, globVec, ADD_VALUES, SCATTER_REVERSE);
> >>> VecView(globVec, PETSC_VIEWER_STDOUT_WORLD);
> >>> PetscViewerFlush(PETSC_VIEWER_STDOUT_WORLD);
> >>>
> >>> PetscFinalize();
> >>> }
> >>>
> >>>
> >>>
> >>>
> >>> --
> >>> 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
> >>>
> >>> https://www.cse.buffalo.edu/~knepley/
> >>>
> >>
> >>
>
>
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