[petsc-users] error handling

[Patrick Sanan]

Just to clarify: are you using PETSc within some larger application, which
you are hoping to continue executing, even after PETSc produces an error?

Am Di., 21. Jan. 2020 um 01:33 Uhr schrieb Sam Guo <sam.guo at cd-adapco.com>:

> Hi Barry,
>   I understand ierr != 0 means  something catastrophic. I just want to
> release all memory before I exit PETSc.
>
> Thanks,
> Sam
>
> On Mon, Jan 20, 2020 at 4:06 PM Smith, Barry F. <bsmith at mcs.anl.gov>
> wrote:
>
>>
>>   Sam,
>>
>>     I am not sure what your goal is but PETSc error return codes are
>> error return codes not exceptions. They mean that something catastrophic
>> happened and there is no recovery.
>>
>>     Note that PETSc solvers do not return nonzero error codes on failure
>> to converge etc. You call, for example, KPSGetConvergedReason() after a KSP
>> solve to see if it has failed, this is not a catastrophic failure. If a
>> MatCreate() or any other call returns a nonzero ierr the game is up, you
>> cannot continue running PETSc.
>>
>>    Barry
>>
>>
>> > On Jan 20, 2020, at 5:41 PM, Matthew Knepley <knepley at gmail.com> wrote:
>> >
>> > Not if you initialize the pointers to zero: Mat A = NULL.
>> >
>> >    Matt
>> >
>> > On Mon, Jan 20, 2020 at 6:31 PM Sam Guo <sam.guo at cd-adapco.com> wrote:
>> > I mean MatDestroy.
>> >
>> > On Mon, Jan 20, 2020 at 3:28 PM Sam Guo <sam.guo at cd-adapco.com> wrote:
>> > Does it hurt to call Destroy function without calling CreateFunction?
>> For example
>> > Mat A, B;
>> > PetscErrorCode  ierr1, ierr2;
>> > ierr1 = MatCreate(PETSC_COMM_WORLD,&A);
>> > if(ierr1 == 0)
>> > {
>> >   ierr2 = MatCreate(PETSC_COMM_WORLD
>> > ,&B);
>> >
>> > }
>> > if(ierr1 !=0 || ierr2 != 0)
>> > {
>> >   Destroy(&A);
>> >   Destroy(&B); // if ierr1 !=0, MatCreat is not called on B. Does it
>> hurt to call Destroy B here?
>> > }
>> >
>> >
>> >
>> > On Mon, Jan 20, 2020 at 11:11 AM Dave May <dave.mayhem23 at gmail.com>
>> wrote:
>> >
>> >
>> > On Mon 20. Jan 2020 at 19:47, Sam Guo <sam.guo at cd-adapco.com> wrote:
>> > Can I assume if there is MatCreat or VecCreate, I should clean up the
>> memory myself?
>> >
>> > Yes. You will need to call the matching Destroy function.
>> >
>> >
>> >
>> > On Mon, Jan 20, 2020 at 10:45 AM Sam Guo <sam.guo at cd-adapco.com> wrote:
>> > I only include the first few lines of SLEPc example. What about
>> following
>> >   ierr = MatCreate(PETSC_COMM_WORLD,&A);CHKERRQ(ierr);
>> >   ierr = MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,n,n);CHKERRQ(ierr);
>> > Is there any memory  lost?
>> >
>> > On Mon, Jan 20, 2020 at 10:41 AM Dave May <dave.mayhem23 at gmail.com>
>> wrote:
>> >
>> >
>> > On Mon 20. Jan 2020 at 19:39, Sam Guo <sam.guo at cd-adapco.com> wrote:
>> > I don't have a specific case yet. Currently every call of PETSc is
>> checked. If ierr is not zero, print the error and return. For example,
>> >    Mat A; /* problem matrix */
>> >    EPS eps; /* eigenproblem solver context */
>> >    EPSType type;
>> >   PetscReal error,tol,re,im;
>> >   PetscScalar kr,ki; Vec xr,xi; 25
>> >   PetscInt n=30,i,Istart,Iend,nev,maxit,its,nconv;
>> >   PetscErrorCode ierr;
>> >   ierr = SlepcInitialize(&argc,&argv,(char*)0,help);CHKERRQ(ierr);
>> >   ierr = PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL);CHKERRQ(ierr);
>> >    ierr = PetscPrintf(PETSC_COMM_WORLD,"\n1-D Laplacian Eigenproblem,
>> n=%D\n\n",n);CHKERRQ(ierr);
>> >
>> > I am wondering if the memory is lost by calling CHKERRQ.
>> >
>> > No.
>> >
>> >
>> >
>> > On Mon, Jan 20, 2020 at 10:14 AM Dave May <dave.mayhem23 at gmail.com>
>> wrote:
>> >
>> >
>> > On Mon 20. Jan 2020 at 19:11, Sam Guo <sam.guo at cd-adapco.com> wrote:
>> > Dear PETSc dev team,
>> >    If PETSc function returns an error, what's the correct way to clean
>> PETSc?
>> >
>> > The answer depends on the error message reported. Send the complete
>> error message and a better answer can be provided.
>> >
>> > Particularly how to clean up the memory?
>> >
>> > Totally depends on the objects which aren’t being freed. You need to
>> provide more information
>> >
>> > Thanks
>> > Dave
>> >
>> >
>> > Thanks,
>> > Sam
>> >
>> >
>> > --
>> > 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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