Well you are doing nothing wrong. When I run the code I get the same results
as you. I dump the matrix into Matlab and it has a negative eigenvalue so the
example is wrong. The code is handling it correctly.
>> eig(full(Mat_0))
ans =
-0.8042
0.1716
0.6489
1.0000
1.0000
1.0000
1.0000
I am cc:iing Victor who supposedly wrote the original example.
Barry
Attached is the matrix saved with -mat_view_matlab
On Aug 23, 2010, at 11:17 PM, Anush Krishnan wrote:
>
> Message: 6
> Date: Mon, 23 Aug 2010 18:40:34 -0500
> From: Barry Smith <bsmith at mcs.anl.gov>
> Subject: Re: [petsc-dev] Problem with conjugate gradient solver
> To: For users of the development version of PETSc
> <petsc-dev at mcs.anl.gov>
> Message-ID: <6432610F-F243-4C9C-AB6A-0944221AE18D at mcs.anl.gov>
> Content-Type: text/plain; charset=us-ascii
>
>
> On Aug 23, 2010, at 2:31 PM, Anush Krishnan wrote:
>
> > Hi,
> >
> > I was trying to compile and run the example file
> > $PETSC_DIR/src/ksp/pc/examples/tutorials/ex3.c, which demonstrates PETSc's
> > preconditioned conjugate gradient solver for a system of linear equations.
> > After compiling, running make runex3 is supposed to throw up the error
> > "Divergence because of indefinite preconditioner" and running make
> > runex3_pd is supposed to work and give the correct solution. But instead I
> > get the error "Other kind of divergence: this should not happen." for the
> > latter. Is there some bug in the code, or are there any other options that
> > need to be set?
>
> Hmm, worked for me.
>
> Please hg pull; hg update then rebuild PETSc and run the make runex3
> runex3_pd again and send the output. I added to that example what reason it
> did have to maybe help determine the problem. Or you can run the example with
> the options given in the makefile and also the option -ksp_converged_reason
>
> I've attached the outputs I got with runex3 and runex3_pd (1 and 2
> respectively. I commented out the statements after the execute commands to
> prevent deletion of the generated output files). This was on revision 16788.
>
> Thanks,
> Anush
>
>
>
> Barry
>
> >
> > Thanks,
> > Anush
> <ex3_inode.out_1><ex3_inode.out_2><ex3.tmp_1><ex3.tmp_2>
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