On Fri, Sep 29, 2017 at 2:37 PM, Sven Verdoolaege
<sven.verdoola...@gmail.com> wrote:
> [Sorry for the resend; I used the wrong email address to CC Alex]
>
> On Wed, Sep 27, 2017 at 02:18:51PM +0200, Richard Biener wrote:
>> Ah, so I now see why we do not perform interchange on trivial cases like
>>
>> double A[1024][1024], B[1024][1024];
>>
>> void foo(void)
>> {
>> for (int i = 0; i < 1024; ++i)
>> for (int j = 0; j < 1024; ++j)
>> A[j][i] = B[j][i];
>> }
>
> I didn't see you mentioning _why_ you expect an interchange here.
> Are you prehaps interested in spatial locality?
> If so, then there are several approaches for taking
> that into account.
> - pluto performs an intra-tile loop interchange to
> improve temporal and/or spatial locality. It shouldn't
> be too hard to do something similar on an isl generated
> schedule
> - Alex (Oleksandr) has been working on an extension of
> the isl scheduler that takes into account spatial locality.
> I'm not sure if it's publicly available.
> - I've been working on a special case of spatial locality
> (consecutivity). The current version is available in
> the consecutivity branch. Note that it may get rebased and
> it may not necessarily get merged into master.
>
> There are also other approaches, but they may not be that
> easy to combine with the isl scheduler.
Would the following work?
Add to the proximity relation the array accesses from two
successive iterations of the innermost loop:
A[j][i] -> A[j][i+1] and B[j][i] -> B[j][i+1]
With these two extra relations in the proximity map,
isl should be able to interchange the above loop.
Sebastian
