On 29/09/17 21:58, Sebastian Pop wrote:
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
Hi,
this looks very close to what we do for spatial locality in the
scheduler, except that we separate proximity and "spatial proximity"
maps. There is a couple of caveats in just plugging those into
proximity, in particular resolving conflicts between spatial and
temporal locality and unnecessary skewing.
Cheers,
Alex
--
Oleksandr Zinenko,
Inria / École Normale Supérieure,
cont...@ozinenko.com, oleksandr.zine...@inria.fr
https://www.ozinenko.com
