> On Oct 21, 2019, at 12:23 AM, Pierre Jolivet <pierre.joli...@enseeiht.fr>
> wrote:
>
>
>
>> On 21 Oct 2019, at 7:11 AM, Smith, Barry F. <bsm...@mcs.anl.gov> wrote:
>>
>>
>>
>>> On Oct 20, 2019, at 11:52 PM, Pierre Jolivet <pierre.joli...@enseeiht.fr>
>>> wrote:
>>>
>>>
>>>
>>>> On 21 Oct 2019, at 6:42 AM, Smith, Barry F. <bsm...@mcs.anl.gov> wrote:
>>>>
>>>> Could you provide a use case where you want to access/have a block size of
>>>> a IS that is not an ISBlock?
>>>
>>> In the end, all I really want is get access to the underlying is->data->idx
>>> without having to worry about the subclass of is.
>>> I don’t have such a use case, but I don’t think this is really related to
>>> what I want to achieve (or maybe it is…).
>>
>> ISGetIndices()
>
> Not true for ISBlock with bs > 1.
Certainly suppose to be, is there a bug?
static PetscErrorCode ISGetIndices_Block(IS in,const PetscInt *idx[])
{
IS_Block *sub = (IS_Block*)in->data;
PetscErrorCode ierr;
PetscInt i,j,k,bs,n,*ii,*jj;
PetscFunctionBegin;
ierr = PetscLayoutGetBlockSize(in->map, &bs);CHKERRQ(ierr);
Dang, there is that stupid layout stuff again. Who put this crap in.
ierr = PetscLayoutGetLocalSize(in->map, &n);CHKERRQ(ierr);
n /= bs;
if (bs == 1) *idx = sub->idx;
else {
ierr = PetscMalloc1(bs*n,&jj);CHKERRQ(ierr);
*idx = jj;
k = 0;
ii = sub->idx;
for (i=0; i<n; i++)
for (j=0; j<bs; j++)
jj[k++] = bs*ii[i] + j;
}
PetscFunctionReturn(0);
}
>
>>> Again, my goal is just to avoid having to write something like:
>>> https://www.mcs.anl.gov/petsc/petsc-dev/src/vec/is/utils/isltog.c.html#line322
>>> If things were done as in ISLocalToGlobalMapping (which I know is not the
>>> same at all as IS/ISBlock), I think this could just read:
>>> ISGetBlockIndices(is,&indices)
>>> ISLocalToGlobalMappingCreate(comm,bs,n/bs,indices,PETSC_COPY_VALUES,mapping)
>>
>> If you want your code to take advantage of the underlying structure of the
>> IS (be it strided, blocked) for optimizations then you HAVE to go through
>> the subclasses by design and nature (for example VecScatterCreate() takes
>> advantage of the structure of the IS as does
>> ISLocalToGlobalMappingCreate()). There is no universal concept of a block
>> size in IS (despite the crap that other people put in using PetscLayout
>> which has nothing to do with ISBlock and is completely buggy.) nor should
>> there be or is there a need for.
>
> OK then.
>
> Thanks,
> Pierre
>
>> Barry
>>
>>
>>
>>
>>>
>>> Thanks,
>>> Pierre
>>>
>>>>
>>>>> On Oct 16, 2019, at 2:50 AM, Pierre Jolivet via petsc-dev
>>>>> <petsc-dev@mcs.anl.gov> wrote:
>>>>>
>>>>> Hello,
>>>>> I’m trying to understand what is the rationale for naming a function
>>>>> ISBlockGetIndices and another ISLocalToGlobalMappingGetBlockIndices
>>>>> (BlockGet vs. GetBlock).
>>>>> Also, it looks to me like the implementation of ISBlockGetIndices is
>>>>> somehow less versatile than ISLocalToGlobalMappingGetBlockIndices.
>>>>> Indeed, I may call ISLocalToGlobalMappingGetBlockIndices with an
>>>>> underlying non-block IS, while I can’t for ISBlockGetIndices, so a check
>>>>> must be performed by the user, e.g.,
>>>>> https://www.mcs.anl.gov/petsc/petsc-current/src/vec/is/is/examples/tutorials/ex3.c.html#line58
>>>>> or this (IMHO) ugly code duplication
>>>>> https://www.mcs.anl.gov/petsc/petsc-dev/src/vec/is/utils/isltog.c.html#line322.
>>>>>
>>>>> Thoughts and/or comments? Would it make sense to add an
>>>>> ISGetBlockIndices/ISRestoreBlockIndices or would that be too confusing
>>>>> for the user?
>>>>>
>>>>> Thanks,
>>>>> Pierre
