[petsc-dev] changed ISCreateGeneral/NC/WithArray()

Barry Smith bsmith at mcs.anl.gov
Sun Oct 3 17:51:18 CDT 2010

   Well it is always "with array" since you always need to provide an array of indices, so why both with the redundant "withArray" (With VecCreateSeqWithArray() there is also a VecCreateSeq() that does not take an array, hence WithArray in that case is not redundant)?

   Regarding having two routines: I found having three almost identical routines unneededly complicated. You still want to have two routines, one is just a subset of the functionality of the second. That is redundant and hence unneeded.
   I do appreciate your suggestions, please keep on having them even if they don't always convince me.


On Oct 3, 2010, at 5:45 PM, Lisandro Dalcin wrote:

> On 3 October 2010 14:57, Barry Smith <bsmith at mcs.anl.gov> wrote:
>>   I find the three routines ISCreateGeneral(), ISCreateGeneralNC() and ISCreateGeneralWithArray() to be confusing and code redundant.
>>   Therefore in PETSc-dev I have introduced
>> /*E
>>    PetscCopyMode  - Determines how an array passed to certain functions is copied or retained
>>   Level: beginner
>> $   PETSC_COPY_VALUES - the array values are copied into new space, the user is free to reuse or delete the passed in array
>> $   PETSC_OWN_POINTER - the array values are NOT copied, the object takes ownership of the array and will free it later, the user cannot change or
>> $                       delete the array. The array MUST have been obtained with PetscMalloc(). Hence this mode cannot be used in Fortran.
>> $   PETSC_USE_POINTER - the array values are NOT copied, the object uses the array but does NOT take ownership of the array. The user cannot use
>>                        the array but the user must delete the array after the object is destroyed.
>> E*/
>> extern const char *PetscCopyModes[];
>> and merged  ISCreateGeneral/NC/WithArray() into a single routine with an additional PetscCopyMode argument.
>> I have also merged ISLocalToGlobalMappingCreate() and ISLocalToGlobalMappingCreateNC() into a single routine.
>> There may be other places we can use this paradigm in the future, keep your eyes open,
>>  Happy computing,
>>    Barry
> I would prefer to have:
> ISCreateGeneralWithArray(comm,n,ptr,copy_mode,&is);
> and then implement
> ISCreateGeneral(comm,n,ptr,&is) {
> return ISCreateGeneralWithArray(comm,n,ptr,PETSC_COPY_VALUES,&is);
> }
> What do you think?
> -- 
> Lisandro Dalcin
> ---------------
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