[petsc-users] petsc-users Digest, Vol 173, Issue 131
Waltz Jan
jl2862237661 at gmail.com
Mon May 29 20:54:56 CDT 2023
Thank you for your reply and help. I followed your advice to try it out,
but found that the results were not quite right. It may be due to my
misunderstanding. Could you please help me? The specific information is as
follows:
Codes:
/* Solve J Y = F, where J is Jacobian matrix */
ierr = SNESComputeJacobian(snes, X, snes->jacobian, snes->jacobian_pre);
CHKERRQ(ierr);
PetscViewer viewer;
/* View the matrix in a text file */
ierr = PetscViewerASCIIOpen(PETSC_COMM_WORLD,
"/share/userfile/jianglei/Muti-layers-well-working/petsc/jacobianmatrix.m",
&viewer);CHKERRQ(ierr);
ierr = PetscViewerPushFormat(viewer, PETSC_VIEWER_ASCII_MATLAB);CHKERRQ(
ierr); /* Optional: use MATLAB format */
ierr = MatView(snes->jacobian, viewer);CHKERRQ(ierr);
ierr = PetscViewerDestroy(&viewer);CHKERRQ(ierr);
MatAssemblyBegin(snes->jacobian,MAT_FINAL_ASSEMBLY);
MatAssemblyEnd(snes->jacobian,MAT_FINAL_ASSEMBLY);
PetscInt rstart, rend;
MatGetOwnershipRange(snes->jacobian, &rstart, &rend);
PetscInt row=1000, col=1000;
PetscScalar v;
if (row>=rstart && row<rend)
{
MatGetValues(snes->jacobian, 1, &row, 1, &col, &v);
PetscPrintf(PETSC_COMM_WORLD, "rstart: %d, rend: %d, row: %d, col: %d,
v: %e\n", rstart, rend, row, col, PetscRealPart(v));
}
Results:
[image: image.png]
[image: image.png]
[image: image.png]
====================== Step: 1, time: 0. days==================== 0 SNES
Function norm 1.772062116708e-01 rstart: 0, rend: 4000, row: 1000, col:
1000, v: 7.443232e-06
That's all. Could you help me?
On Tue, May 30, 2023 at 1:00 AM <petsc-users-request at mcs.anl.gov> wrote:
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> Today's Topics:
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> 1. MatGetValues() can't return the correct values (Waltz Jan)
> 2. Re: MatGetValues() can't return the correct values (Barry Smith)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Mon, 29 May 2023 16:49:40 +0800
> From: Waltz Jan <jl2862237661 at gmail.com>
> To: petsc-users at mcs.anl.gov
> Subject: [petsc-users] MatGetValues() can't return the correct values
> Message-ID:
> <CAEj=jGKvgY5ys=4_=YoEZrE5Xu4Pj6FVxSq8XgUH=N=
> QF_C-vA at mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> /* Solve J Y = F, where J is Jacobian matrix */
> ierr = SNESComputeJacobian(snes, X, snes->jacobian, snes->jacobian_pre);
> CHKERRQ(ierr);
>
> PetscInt rstart, rend;
> MatGetOwnershipRange(snes->jacobian, &rstart, &rend);
> PetscInt row=1000, col=1000;
> PetscScalar v;
> if (row>=rstart && row<rend)
> {
> MatGetValues(snes->jacobian, 1, &row, 1, &col, &v);
> PetscPrintf(PETSC_COMM_WORLD, "rstart: %d, rend: %d, row: %d, col: %d,
> v: %e\n", rstart, rend, row, col, v);
> }
>
> It was supposed to return the value of the matrix at row 1001 and column
> 1001, but it returned the value at row 2001 and column 2001 instead. There
> is a two-fold relationship between these coordinates, and I'm not sure if
> it's related to the fact that I set the number of processes to 2.
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> Message: 2
> Date: Mon, 29 May 2023 11:01:32 -0400
> From: Barry Smith <bsmith at petsc.dev>
> To: Waltz Jan <jl2862237661 at gmail.com>
> Cc: petsc-users at mcs.anl.gov
> Subject: Re: [petsc-users] MatGetValues() can't return the correct
> values
> Message-ID: <99A3D1B8-6CA1-41C3-8B19-E68F90A67102 at petsc.dev>
> Content-Type: text/plain; charset="us-ascii"
>
>
> Perhaps run a very small problem with 2 ranks and use MatView() to see
> the matrix before getting the values. Maybe use the debugger
> (-start_in_debugger) and step through the code as it gets values. I would
> say there is very little chance it is getting the "wrong values" and is
> more likely due to a misunderstanding of the matrix usage.
>
> Barry
>
>
>
>
> > On May 29, 2023, at 4:49 AM, Waltz Jan <jl2862237661 at gmail.com> wrote:
> >
> > /* Solve J Y = F, where J is Jacobian matrix */
> > ierr = SNESComputeJacobian(snes, X, snes->jacobian, snes->jacobian_pre);
> > CHKERRQ(ierr);
> >
> > PetscInt rstart, rend;
> > MatGetOwnershipRange(snes->jacobian, &rstart, &rend);
> > PetscInt row=1000, col=1000;
> > PetscScalar v;
> > if (row>=rstart && row<rend)
> > {
> > MatGetValues(snes->jacobian, 1, &row, 1, &col, &v);
> > PetscPrintf(PETSC_COMM_WORLD, "rstart: %d, rend: %d, row: %d, col:
> %d, v: %e\n", rstart, rend, row, col, v);
> > }
> >
> > It was supposed to return the value of the matrix at row 1001 and column
> 1001, but it returned the value at row 2001 and column 2001 instead. There
> is a two-fold relationship between these coordinates, and I'm not sure if
> it's related to the fact that I set the number of processes to 2.
>
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