[petsc-users] empty split for fieldsplit

Tue Jun 20 10:24:17 CDT 2017

The fix is merged to master branch.
Thanks for your report and contribution!
Hong

On Mon, Jun 19, 2017 at 4:35 AM, Hoang Giang Bui <hgbk2008 at gmail.com> wrote:

> Thanks Hong
>
> I confirmed that it's fixed by your changes.
>
> Giang
>
> On Sun, Jun 18, 2017 at 4:45 PM, Hong <hzhang at mcs.anl.gov> wrote:
>
>> Hoang,
>> I pushed a fix
>> https://bitbucket.org/petsc/petsc/commits/d4e3277789d24018f0
>> db1641a80db7be76600165
>> and added your test to
>> petsc/src/ksp/ksp/examples/tests/ex53.c
>>
>> It is on the branch hzhang/fix-blockedIS-submat
>> Let me know if it still does not fix your problem.
>>
>> Hong
>>
>> On Sat, Jun 17, 2017 at 4:06 PM, Zhang, Hong <hzhang at mcs.anl.gov> wrote:
>>
>>> never mind, I know it is ok to set blocksize=2
>>> ------------------------------
>>> *From:* Zhang, Hong
>>> *Sent:* Saturday, June 17, 2017 3:56:35 PM
>>>
>>> *To:* Smith, Barry F.; Hoang Giang Bui
>>> *Cc:* petsc-users
>>> *Subject:* Re: [petsc-users] empty split for fieldsplit
>>>
>>>
>>> Matrix A is a tridiagonal matrix with blocksize=1.
>>>
>>> Why do you set block_size=2 for A_IS and B_IS?
>>>
>>>
>>> Hong
>>> ------------------------------
>>> *From:* Zhang, Hong
>>> *Sent:* Friday, June 16, 2017 7:55:45 AM
>>> *To:* Smith, Barry F.; Hoang Giang Bui
>>> *Cc:* petsc-users
>>> *Subject:* Re: [petsc-users] empty split for fieldsplit
>>>
>>>
>>> I'm in Boulder and will be back home this evening.
>>>
>>> Will test it this weekend.
>>>
>>>
>>> Hong
>>> ------------------------------
>>> *From:* Smith, Barry F.
>>> *Sent:* Thursday, June 15, 2017 1:38:11 PM
>>> *To:* Hoang Giang Bui; Zhang, Hong
>>> *Cc:* petsc-users
>>> *Subject:* Re: [petsc-users] empty split for fieldsplit
>>>
>>>
>>>    Hong,
>>>
>>> Please build the attached code with master and run with
>>>
>>> petscmpiexec -n 2 ./ex1 -mat_size 40 -block_size 2 -method 2
>>>
>>> I think this is a bug in your new MatGetSubMatrix routines. You take the
>>> block size of the outer IS and pass it into the inner IS but that inner IS
>>> may not support the same block size hence the crash.
>>>
>>>    Can you please debug this?
>>>
>>>     Thanks
>>>
>>>      Barry
>>>
>>>
>>>
>>> > On Jun 15, 2017, at 7:56 AM, Hoang Giang Bui <hgbk2008 at gmail.com>
>>> wrote:
>>> >
>>> > Hi Barry
>>> >
>>> > Thanks for pointing out the error. I think the problem coming from the
>>> zero fieldsplit in proc 0. In this modified example, I parameterized the
>>> matrix size and block size, so when you're executing
>>> >
>>> > mpirun -np 2 ./ex -mat_size 40 -block_size 2 -method 1
>>> >
>>> > everything was fine. With method = 1, fieldsplit size of B is nonzero
>>> and is divided by the block size.
>>> >
>>> > With method=2, i.e mpirun -np 2 ./ex -mat_size 40 -block_size 2
>>> -method 2, the fieldsplit B is zero on proc 0, and the error is thrown
>>> >
>>> > [1]PETSC ERROR: --------------------- Error Message
>>> --------------------------------------------------------------
>>> > [1]PETSC ERROR: Arguments are incompatible
>>> > [1]PETSC ERROR: Local size 11 not compatible with block size 2
>>> >
>>> > This is somehow not logical, because 0 is divided by block_size.
>>> >
>>> > Furthermore, if you execute  "mpirun -np 2 ./ex -mat_size 20
>>> -block_size 2 -method 2", the code hangs at ISSetBlockSize, which is pretty
>>> similar to my original problem. Probably the original one also hangs at
>>> ISSetBlockSize, which I may not realize at that time.
>>> >
>>> > Giang
>>> >
>>> > On Wed, Jun 14, 2017 at 5:29 PM, Barry Smith <bsmith at mcs.anl.gov>
>>> wrote:
>>> >
>>> > 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/d
>>> ocumentation/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/te
>>> st-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>
>>> >
>>> >
>>> > <ex.c>
>>>
>>>
>>
>
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