OpenCL vs. DirectCompute?

Question

I'm looking for comparisons between OpenCL and DirectCompute, but I haven't found anything. OpenCL's advantages of being cross-platform and having a wider range of supported GPUs don't matter to me. I'm fine with coding on Windows against DX11 GPUs only. Assuming that, what are the pros and cons of each API?

I know this question was raised before, but I'm looking for more details.

I'm not interested in CUDA, since I don't want to restrict myself to only Nvidia hardware.

Answer 1

Probably the biggest difference for a coder is that DirectCompute is programmed by a language which is similar to HLSL, and OpenCL is programmed via a C-like language.

Another difference to consider is that, generally, for commodity level GPUs, the DirectX support is better (faster and less buggy) than OpenGL support on Windows. This may translate to more stable support for DirectCompute, but really, this is just speculation.

Answer 2

Well the major advantage of OpenCL is that it is not just limited to graphics cards. You can make use of your multicore CPU, Graphics Card and potentially any number of other hardware acceleration devices (DSPs etc) all from the same program.

I'm not sure if DirectCompute allows that freedom.

Answer 3

The OpenCL cross-platform-ness is not just a detail, as the host code (the one calling the OpenCL API and submitting kernels) can itself be cross-platform (see link text, link text...).

Write once, run on any GPGPU, anywhere.

Otherwise the OpenCL tooling is really getting better, with an ATI Stream plugin for Visual Studio, the NVidia & ATI SDKs that contains tons of samples, etc...

Answer 4

Another option now is C++ AMP which gives you modern C++ syntax without a need for a seperate compiler while still preserving hardware portability. Please follow links from here for more info and feel free to post questions as you have them: http://blogs.msdn.com/b/nativeconcurrency/archive/2011/09/13/c-amp-in-a-nutshell.aspx

Answer 5

I use OpenCL because i can easily port my App to Linux but with DirectCompute this is not possible. I think also that the performance of the OpenCL implementation will increase with time (that it comes at the same Level like CUDA for NVidia Cards) and also that the (driver)bugs will (hopefully ;) ) be eliminated with time.