dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Thu, Nov 15, 2012 at 09:09:52PM +0000, Garth N. Wells wrote:
> The first stage of the transition to a new integer type is complete.

Great!

> Most of DOLFIN now uses std::size_t, and a new typedef 'DolfinIndex'
> has been introduced for compatibility with linear algebra backends.
> Please feel free to suggest a better name for this typedef. Presently,
> DolfinIndex is just a typedef for int. This typedef should rarely be
> visible to a user, and it should have a name that discourages its
> unnecessary use.

I'm a bit confused. We now have

PETScMatrix::add(const double* block, std::size_t m, const DolfinIndex* rows,
                                      std::size_t n, const DolfinIndex* cols);

Here, the only thing being size_t is the dimension of the local
stiffness matrix, which is never big (so the 4 bytes of uint should
be sufficient). On the other hand the rows and cols pointers contain
global indices and they now use int which have an even smaller range
than uint. I would expect to have

PETScMatrix::add(const double* block, uint m, size_t* rows,
                                      uint n, size_t* cols);

or size_t all over.

And if we want to use PETSc for large index ranges, then we need to
use PETScInt which may or may not be compatible with size_t.

--
Anders


> There are some small changes on the Python size, most notably the need
> to use "sizet" in place of "uint" for MeshFunctions. One can create
> both uint (unsigned int)  and sizet (std::size_t) MeshFunctions, but
> most interfaces expect sizet. We could eliminate the "uint" versions
> and map "uint" to the sizet case. Opinions?
>
> Some thought is required to figure out the mapping to numpy integer
> types. std::size_t is easy because numpy has a type 'uintp' which is
> the same as std::size_t. Dealing with DolfinIndex is harder because
> figuring out its type from the SWIG side doesn't seem easy. One
> solution is to use more data copying for in typemaps.
>
> Garth
>
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