On Mon, 4 Jun 2018 at 21:36, Ilia Mirkin <imir...@alum.mit.edu> wrote:
> On Mon, Jun 4, 2018 at 4:30 PM, Plamena Manolova > <plamena.n.manol...@gmail.com> wrote: > > Thank you for the review Ilia! > > > > On Fri, 1 Jun 2018 at 23:44, Ilia Mirkin <imir...@alum.mit.edu> wrote: > >> > >> On Fri, Jun 1, 2018 at 6:21 PM, Plamena Manolova > >> <plamena.n.manol...@gmail.com> wrote: > >> > + /* > >> > + * If the local work group size is variable we have to use a > >> > dispatch > >> > + * width of 32 here, since at this point we don't know the > actual > >> > size of > >> > + * the workload. > >> > + */ > >> > + min_dispatch_width = 32; > >> > >> Is that a good idea? You are able to specify a different maximum when > >> using a variable size (MAX_COMPUTE_VARIABLE_GROUP_INVOCATIONS_ARB) > >> s.t. this is 16 (or even 8, although that may be too few for practical > >> use) -- that way you would just set the max to 768 or whatever on > >> gen8+. > > > > > > That's a good point, MAX_COMPUTE_VARIABLE_GROUP_INVOCATIONS_ARB is the > > same on all platforms, so it makes sense to use simd16 instead. Thank you > > for noticing that. > > Well IIRC gen7/gen7.5 can do something like 1536 invocations with > SIMD16, while gen8 are down to 768. Either way, not forcing SIMD32 may > be nice -- but that's something for you Intel folk to decide. I just > wanted to point out that you could have different max's for "regular" > compute (where the min max is 1024) and variable-size groups. > Ah, I see what you mean now. I took a closer look at MAX_COMPUTE_VARIABLE_GROUP_INVOCATIONS_ARB and it's related to the maximum number of CS threads (which of course varies). > -ilia >
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