[petsc-users] error handling

[Matthew Knepley]

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 <https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Sys/PetscErrorCode.html#PetscErrorCode>  ierr1, ierr2;
>>
>> ierr1 = MatCreate <https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatCreate.html#MatCreate>(PETSC_COMM_WORLD <https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Sys/PETSC_COMM_WORLD.html#PETSC_COMM_WORLD>,&A);
>>
>> if(ierr1 == 0)
>>
>> {
>>
>>   ierr2 = MatCreate <https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatCreate.html#MatCreate>(PETSC_COMM_WORLD <https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Sys/PETSC_COMM_WORLD.html#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/ <http://www.cse.buffalo.edu/~knepley/>
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