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digitalmars.D.learn - using DCompute

reply James Dean <JamesDean MTV.com> writes:
I'm interested in trying it out, says it's just for ldc. Can we 
simply compile it using ldc then import it and use dmd, ldc, or 
gdc afterwards?

---
a SPIRV capable LLVM (available here to build ldc to to support 
SPIRV (required for OpenCL)).
or LDC built with any LLVM 3.9.1 or greater that has the NVPTX 
backend enabled, to support CUDA.
---

Is the LDC from the download pages have these enabled?

Also, can DCompute or any GPU stuff efficiently render stuff 
because it is already on the GPU or does one sort of have to jump 
through hoops to, say, render a buffer?

e.g., suppose I want to compute a 3D mathematical function and 
visualize it's volume. Do I go in to the GPU, do the compute, 
back out to cpu, then to the graphics system(opengl/directX) or 
can I just essentially do it all from the gpu?
Jul 27 2017
parent reply Nicholas Wilson <iamthewilsonator hotmail.com> writes:
On Thursday, 27 July 2017 at 21:33:29 UTC, James Dean wrote:

 I'm interested in trying it out, says it's just for ldc. Can we 
 simply compile it using ldc then import it and use dmd, ldc, or 
 gdc afterwards?


The ability to write kernels is limited to LDC, though there is 
no practical reason that, once compiled, you couldn't use 
resulting generated files with GDC or DMD (as long as the 
mangling matches, which it should). This is not a priority to get 
working, since the assumption is if you're trying to use the GPU 
to boost your computing power, then you like care enough to use 
LDC, as opposed to DMD (GDC is still a bit behind DMD so I don't 
consider it) to get good optimisations in the first place.


 ---
 a SPIRV capable LLVM (available here to build ldc to to support 
 SPIRV (required for OpenCL)).
 or LDC built with any LLVM 3.9.1 or greater that has the NVPTX 
 backend enabled, to support CUDA.
 ---

 Is the LDC from the download pages have these enabled?


I dont think so, although future releases will likely have the 
NVPTX backend enabled.


 Also, can DCompute or any GPU stuff efficiently render stuff 
 because it is already on the GPU or does one sort of have to 
 jump through hoops to, say, render a buffer?


There are memory sharing extensions that allow you to give access 
to and from OpenGL/DirectX so you shouldn't suffer a perf penalty 
for doing so.


 e.g., suppose I want to compute a 3D mathematical function and 
 visualize it's volume. Do I go in to the GPU, do the compute, 
 back out to cpu, then to the graphics system(opengl/directX) or 
 can I just essentially do it all from the gpu?


there should be no I/O overhead.
Jul 27 2017
parent reply James Dean <JamesDean MTV.com> writes:
On Friday, 28 July 2017 at 00:23:35 UTC, Nicholas Wilson wrote:

 On Thursday, 27 July 2017 at 21:33:29 UTC, James Dean wrote:

 I'm interested in trying it out, says it's just for ldc. Can 
 we simply compile it using ldc then import it and use dmd, 
 ldc, or gdc afterwards?


 The ability to write kernels is limited to LDC, though there is 
 no practical reason that, once compiled, you couldn't use 
 resulting generated files with GDC or DMD (as long as the 
 mangling matches, which it should). This is not a priority to 
 get working, since the assumption is if you're trying to use 
 the GPU to boost your computing power, then you like care 
 enough to use LDC, as opposed to DMD (GDC is still a bit behind 
 DMD so I don't consider it) to get good optimisations in the 
 first place.


Yes, but dmd is still good for development since LDC sometimes 
has problems.

Can we compile kernels in LDC and import them in to a D project 
seamlessly? Basically keep an LDC project that deals with the 
kernels while using dmd for the bulk of the program. I mean, is 
it a simple import/export type of issue?
Jul 27 2017
parent reply Nicholas Wilson <iamthewilsonator hotmail.com> writes:
On Friday, 28 July 2017 at 00:39:43 UTC, James Dean wrote:

 On Friday, 28 July 2017 at 00:23:35 UTC, Nicholas Wilson wrote:

 On Thursday, 27 July 2017 at 21:33:29 UTC, James Dean wrote:

 I'm interested in trying it out, says it's just for ldc. Can 
 we simply compile it using ldc then import it and use dmd, 
 ldc, or gdc afterwards?


 The ability to write kernels is limited to LDC, though there 
 is no practical reason that, once compiled, you couldn't use 
 resulting generated files with GDC or DMD (as long as the 
 mangling matches, which it should). This is not a priority to 
 get working, since the assumption is if you're trying to use 
 the GPU to boost your computing power, then you like care 
 enough to use LDC, as opposed to DMD (GDC is still a bit 
 behind DMD so I don't consider it) to get good optimisations 
 in the first place.


 Yes, but dmd is still good for development since LDC sometimes 
 has problems.


If you have problems please tell us!


 Can we compile kernels in LDC and import them in to a D project 
 seamlessly? Basically keep an LDC project that deals with the 
 kernels while using dmd for the bulk of the program. I mean, is 
 it a simple import/export type of issue?


Yes, although I'll have to add an attribute shim layer for the 
dcompute druntime symbols to be accessible for DMD. When you 
compile LDC will produce .ptx and .spv files in the object file 
directory which will be able to be used in any project. The only 
thing that will be more fragile is lambda kernels as they are 
mangled numerically (`__lambda1`, `__lambda1` and so on).
Jul 27 2017
parent jmh530 <john.michael.hall gmail.com> writes:
On Friday, 28 July 2017 at 01:30:58 UTC, Nicholas Wilson wrote:

 Yes, although I'll have to add an attribute shim layer for the 
 dcompute druntime symbols to be accessible for DMD. When you 
 compile LDC will produce .ptx and .spv files in the object file 
 directory which will be able to be used in any project. The 
 only thing that will be more fragile is lambda kernels as they 
 are mangled numerically (`__lambda1`, `__lambda1` and so on).


I imagine that using dcompute this way with DMD for development 
would be popular. For instance, the GPU part might be only a 
small part of a project so you wouldn't want to be forced to use 
LDC the moment the tiniest GPU code is in it.

Once you've ensured everything is working correctly, you might 
add something about this to the wiki, or whatever.
Jul 27 2017