[petsc-users] error handling

[Sam Guo]

Thanks.

On Tue, Jan 21, 2020 at 11:03 AM Jeremy Theler <jeremy at seamplex.com> wrote:

> Dear Sam
>
> Probably you are already aware of the following paragraph, but just in
> case. Quote from
> https://www.gnu.org/prep/standards/standards.html#Memory-Usage
>
>
> Memory analysis tools such as valgrind can be useful, but don’t
> complicate a program merely to avoid their false alarms. For example,
> if memory is used until just before a process exits, don’t free it
> simply to silence such a tool.
>
>
> Regards
> --
> jeremy theler
> www.seamplex.com
>
>
>
> On Tue, 2020-01-21 at 08:49 -0800, Sam Guo wrote:
> > I use PETSc from my application. Sounds you are saying I just treat
> > ierr!=0 as an system error and no need to call Destroy functions.
> >
> > On Tuesday, January 21, 2020, Smith, Barry F. <bsmith at mcs.anl.gov>
> > wrote:
> > >
> > > > On Jan 20, 2020, at 6:32 PM, Sam Guo <sam.guo at cd-adapco.com>
> > > wrote:
> > > >
> > > > Hi Barry,
> > > >   I understand ierr != 0 means  something catastrophic. I just
> > > want to release all memory before I exit PETSc.
> > >
> > >    In general not possible. If you run with the debug version and
> > > -malloc_debug it is possible but because of the unknown error it
> > > could be that the releasing of the memory causes a real crash.
> > >
> > >    Is your main concern when you use PETSc for a large problem and
> > > it errors because it is "out of memory"?
> > >
> > >    Barry
> > >
> > >
> > > >
> > > > 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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