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  • Dec 09 23:49
    abadams commented #4461
  • Dec 09 23:36
    dsharletg commented #4461
  • Dec 09 23:28
    dsharletg commented #4461
  • Dec 09 23:25
    dsharletg commented #4461
  • Dec 09 23:24
    dsharletg synchronize #4461
  • Dec 09 23:24

    dsharletg on fix-fft

    Fix even smaller FFTs. (compare)

  • Dec 09 22:54
    alexreinking assigned #4284
  • Dec 09 22:52
    alexreinking assigned #4424
  • Dec 09 22:48
    alexreinking closed #2946
  • Dec 09 21:20
    kpassarella commented #4276
  • Dec 09 21:11
    alexreinking commented #4439
  • Dec 09 21:06
    abadams commented #4439
  • Dec 09 20:45
    akokoshn commented #4459
  • Dec 09 20:13
    alexreinking commented #4439
  • Dec 09 19:34
    abadams commented #4461
  • Dec 09 19:34
    dsharletg commented #4461
  • Dec 09 19:34
    dsharletg edited #4461
  • Dec 09 19:26
    dsharletg opened #4461
  • Dec 09 19:23

    dsharletg on fix-fft

    Fix bad vectorize directive for… Fix fft2d_c2r reaching out of b… (compare)

  • Dec 09 19:11
    dsharletg commented #4276
Zalman Stern
@zvookin
So I think we need to keep the current model, but we should consider introducing a new one that allows much more asynchrony.
Whether that is just async versions of the copy routines or a full event model I'm not sure
I'm not sure it makes much sense to consider until we are looking at a different way of lowering async
I.e. in the current model, synchronous copy is probably required anyway. The thread doing it would just wait immediately if it wasn't synchronous.
"Event model" likely amounts to exposing the semaphore abstraction and arranging for it to be signaled by the device support code somehow
Andrew Adams
@abadams
Overlapping CPU computation with device stuff works fine. All use of the device_api occurs on a single thread. All the CPU compute occurs on another thread.
That's what I'm targeting for now
Zalman Stern
@zvookin
"CPU" is not necessarily correct there. It can be a different device too.
That is the common case for Hexagon right?
Andrew Adams
@abadams
For the hexagon DMA work so far, "CPU" is hexagon, and "device" is the dma engine
Zalman Stern
@zvookin
Ok, but the Hexagon may be invoked via offload.
Andrew Adams
@abadams
But yeah, I think it would work to have cross-device stuff going on in parallel
All use of each device interface would be on a single distinct thread
Zalman Stern
@zvookin
yes
Andrew Adams
@abadams
and there's no cross-device-interface serialization I think
so it would just work
Zalman Stern
@zvookin
That is what I was highlighting.
The only issue I see with this design is that the overhead of the thread may be too high to use for very lightweight hardware synchronization mechanisms. Other than that, I don't see a lot of reason to do the customized lowering.
I need to make a couple more changes to the hexagon DMA
Will try to do so today.
The test only calls buffer_copy, which is mostly as it should be.
Dillon Sharlet
@dsharletg
So BTW regarding hexagon offloading, I've been thinking we simply punt on that for now
and only target standalone
anything that we get working on standalone can be made to work with offloading without solving any "hard" problems like async + storage folding, it just might involve a lot of plumbing and infrastructure
Steven Johnson
@steven-johnson
re: the windows buildbots, proposed fix is out there.
Zalman Stern
@zvookin
I'll have to consider the implications, but I think the current stuff just works if the DMA things are scheduled inside an offloaded thing.
Dillon Sharlet
@dsharletg
I think there might be some hiccups with the device interface
that will need to get plumbed over via offloading
and I don't think that will happen transparently right now
it might be easy to make it work though
Zalman Stern
@zvookin
yeah, that's small boogs territory.
I guess I'm expecting it will have to work with offload very early on to have a useful test.
Andrew Adams
@abadams
@dsharletg the host->device case also works, but there's no benefit for cuda because the version without async already manages to overlap the cpu compute and copies in a subtle way.
Confused me for a while.
CPU compute -> synchronous copy -> async kernel launch -> next batch of CPU compute (overlapped with GPU kernel launch) -> synchronous copy (stalls until kernel launch is done) ->
Wait, so I guess the CPU compute is hidden under the GPU compute
not the copy
Dillon Sharlet
@dsharletg
That's great news!
Steven Johnson
@steven-johnson
I’m restarting the buildbot master now
Steven Johnson
@steven-johnson
On the recent issue of exported symbols varying between opt levels: it looks like CMake added a feature in 3.4 that attempts to auto-build a .def file for you on Windows, with the net effect of (mostly) acting like the gcc-ish default of “export all symbols”: https://blog.kitware.com/create-dlls-on-windows-without-declspec-using-new-cmake-export-all-feature/
I haven’t tried it (and we are talking about CMake here so who knows)...
Steven Johnson
@steven-johnson
We explicitly forbid using ‘.’ in a Func name since we use that as a separator internally, but we don’t seem to have a similar constraint on Var name. Deliberate or accidental?
Andrew Adams
@abadams
Var names are not uniqued either
Accidental I think
Zalman Stern
@zvookin
Var names are not uniqued by design
They're value types
Steven Johnson
@steven-johnson
Right
Andrew Adams
@abadams
Lack of '.' enforcement is the accidental thing
Steven Johnson
@steven-johnson
Just idly wondering if more constraints on the names allowed would give us more flexibility in the future. (e.g. GeneratorParam names are limited to C-style identifier rules, with additional constraints on underscore usage). Probably overthinking it.
Re: the windows buildbots: I updated the scripts and did a buildbot stop and start, but builds completing since then still seem to be using the old, broken windows testing approach. I wonder, do the workers queue up the commands on the worker (and thus this could be just stale builds completing)? Investigating...