Subject: Graphics Cards | August 2, 2017 - 07:01 AM | Scott Michaud
Tagged: spir-v, opengl, Khronos
While Vulkan has been getting a lot of mindshare recently, OpenGL is still in active development. This release, OpenGL 4.6, adds a bunch of extensions into the core specification, making them more reliably available to engines. There’s a lot of them this time, many of which seem to borrow design elements from the work done on Vulkan.
The headlining feature is SPIR-V support as an ARB extension, which frees OpenGL programs from having their shaders written in GLSL. Many engines write their shaders in HLSL and use a transpiler to generate the corresponding GLSL, which may not support all features. The extension might also help titles target both OpenGL and Vulkan, although I’m not sure why we would see a driver that supports OpenGL 4.6 but not Vulkan.
Another extension is GL_KHR_no_error, which tells graphics drivers that they do not need to generate errors at runtime. This will save a bit of driver overhead. GL_ARB_indirect_parameters also helps with CPU overhead by allowing draws to pass parameters to other GPU-initiated draws, although this is a bit out of my domain. Also, if you’re not working in SPIR-V, GL_KHR_parallel_shader_compile will allow the driver to compile your GLSL shaders across multiple worker threads.
NVIDIA has a beta driver for developers, which is a couple of versions back compared to their consumer version, so you don’t want to install it unless you intend on developing OpenGL 4.6 applications. Mesa says that they shouldn’t be too far behind.
Subject: Editorial | May 18, 2017 - 11:46 AM | Alex Lustenberg
Tagged: youtube tv, western digital, video, Vega, Threadripper, spir-v, ryzen, podcast, opencl, Google VR, EPYC, Core i9, battletech, amd
PC Perspective Podcast #450 - 05/18/17
Join us for AMD Announcments, Core i9 leaks, OpenCL updates, and more!
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Hosts: Ryan Shrout, Jeremy Hellstrom, Josh Walrath, Allyn Malventano
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Ryan: Gigabit LTE please hurry
Allyn: TriboTEX (nanotech engine oil additive)
Subject: General Tech | May 16, 2017 - 09:00 AM | Scott Michaud
Tagged: spir-v, opencl, Khronos
Aligning with the start of the International Workshop on OpenCL (IWOCL) 2017 in Toronto, Ontario, Canada, The Khronos Group has published the finalized specification for OpenCL 2.2 and SPIR-V 1.2. The headlining feature for this release is the OpenCL C++ kernel language, which SPIR-V 1.2 fully supports. Kernels are the portion of code that execute on the compute devices, such as GPUs, FPGAs, super computers, multi-core CPUs, and so forth.
The OpenCL C++ kernel language is a subset of the C++14 standard, bringing many of its benefits to these less-general devices. Classes help data and code to be more tightly integrated. Templates help define logic in a general way for whatever data type implements whatever it requires, which is useful for things like custom containers. Lambda expressions make it easy to write one-off methods, rather than forcing the developer to name something that will only be used once, like comparing two data types for a special sort in one specific spot of code.
Exposing these features to the OpenCL device also enables The Khronos Group to further the SYCL standard, which aims for “single-source” OpenCL development. Having the code that executes on OpenCL-compatible devices contain roughly the same features as the host code is kind-of necessary to let them be written together, rather than exist as two pools.
Subject: Graphics Cards | January 27, 2017 - 09:19 PM | Scott Michaud
Tagged: microsoft, DirectX, llvm, dxil, spir-v, vulkan
Over the holidays, Microsoft has published the DirectX Shader Compiler onto GitHub. The interesting part about this is that it outputs HLSL into DirectX Intermediate Language (DXIL) bytecode, which can be ingested by GPU drivers and executed on graphics devices. The reason why this is interesting is that DXIL is based on LLVM, which might start to sound familiar if you have been following along with The Khronos Group and their announcements regarding Vulkan, OpenCL, and SPIR-V.
As it turns out, they were on to something, and Microsoft is working on a DirectX analogue of it.
The main advantage of LLVM-based bytecode is that you can eventually support multiple languages (and the libraries of code developed in them). When SPIR-V was announced with Vulkan, the first thing that came to my mind was compiling to it from HLSL, which would be useful for existing engines, as they are typically written in HLSL and transpiled to the target platform when used outside of DirectX (like GLSL for OpenGL). So, in Microsoft’s case, it would make sense that they start there (since they own the thing) but I doubt that is the end goal. The most seductive outcome for game engine developers would be single-source C++, but there is a lot of steps between there and here.
Another advantage, albeit to a lesser extent, is that you might be able to benefit from performance optimizations, both on the LLVM / language side as well as on the driver’s side.
According to their readme, the minimum support will be HLSL Shader Model 6. This is the most recent shading model, and it introduces some interesting instructions, typically for GPGPU applications, that allow multiple GPU threads to interact, like balloting. Ironically, while DirectCompute and C++AMP don’t seem to be too popular, this would nudge DirectX 12 into a somewhat competent GPU compute API.
DXIL support is limited to Windows 10 Build 15007 and later, so you will need to either switch one (or more) workstation(s) to Insider, or wait until it launches with the Creators Update (unless something surprising holds it back).