[petsc-users] empty split for fieldsplit

[Barry Smith]

You can't do this

   ierr = MatSetSizes(A,PETSC_DECIDE,N,N,N);CHKERRQ(ierr);

  use PETSC_DECIDE for the third argument

Also this is wrong

  for (i = Istart; i < Iend; ++i)
   {
       ierr = MatSetValue(A,i,i,2,INSERT_VALUES);CHKERRQ(ierr);
       ierr = MatSetValue(A,i+1,i,-1,INSERT_VALUES);CHKERRQ(ierr);
       ierr = MatSetValue(A,i,i+1,-1,INSERT_VALUES);CHKERRQ(ierr);
   }

you will get 

$ petscmpiexec -n 2 ./ex1
0: Istart = 0, Iend = 60
1: Istart = 60, Iend = 120
[1]PETSC ERROR: --------------------- Error Message --------------------------------------------------------------
[1]PETSC ERROR: Argument out of range
[1]PETSC ERROR: Row too large: row 120 max 119
[1]PETSC ERROR: See http://www.mcs.anl.gov/petsc/documentation/faq.html for trouble shooting.
[1]PETSC ERROR: Petsc Development GIT revision: v3.7.6-4103-g93161b8192  GIT Date: 2017-06-11 14:49:39 -0500
[1]PETSC ERROR: ./ex1 on a arch-basic named Barrys-MacBook-Pro.local by barrysmith Wed Jun 14 18:26:52 2017
[1]PETSC ERROR: Configure options PETSC_ARCH=arch-basic
[1]PETSC ERROR: #1 MatSetValues_MPIAIJ() line 550 in /Users/barrysmith/Src/petsc/src/mat/impls/aij/mpi/mpiaij.c
[1]PETSC ERROR: #2 MatSetValues() line 1270 in /Users/barrysmith/Src/petsc/src/mat/interface/matrix.c
[1]PETSC ERROR: #3 main() line 30 in /Users/barrysmith/Src/petsc/test-dir/ex1.c
[1]PETSC ERROR: PETSc Option Table entries:
[1]PETSC ERROR: -malloc_test

You need to get the example working so it ends with the error you reported previously not these other bugs.


> On Jun 12, 2017, at 10:19 AM, Hoang Giang Bui <hgbk2008 at gmail.com> wrote:
> 
> Dear Barry
> 
> I made a small example with 2 process with one empty split in proc 0. But it gives another strange error
> 
> [1]PETSC ERROR: --------------------- Error Message --------------------------------------------------------------
> [1]PETSC ERROR: Arguments are incompatible
> [1]PETSC ERROR: Local size 31 not compatible with block size 2
> 
> The local size is always 60, so this is confusing.
> 
> Giang
> 
> On Sun, Jun 11, 2017 at 8:11 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>   Could be, send us a simple example that demonstrates the problem and we'll track it down.
> 
> 
> > On Jun 11, 2017, at 12:34 PM, Hoang Giang Bui <hgbk2008 at gmail.com> wrote:
> >
> > Hello
> >
> > I noticed that my code stopped very long, possibly hang, at PCFieldSplitSetIS. There are two splits and one split is empty in one process. May that be the possible reason that PCFieldSplitSetIS hang ?
> >
> > Giang
> 
> 
> <ex.c>