Vulkan 1.1.116 Published With Subgroup Size Control Extension
Written by Michael Larabel in Vulkan on 21 July 2019 at 04:00 PM EDT. 8 Comments
Vulkan 1.1.116 was released today as the latest weekly update to this high performance graphics API and comes with one new extension in tow.

Vulkan 1.1.116 includes the usual documentation corrections/fixes, but making this release notable is the introduction of a new extension for having control over the subgroup sizes.

The new VK_EXT_subgroup_size_control extension was worked on by folks from NVIDIA, Intel, Google, AMD, Qualcomm, Broadcom. and even EA. Yes, it's a biggie. It allows for enabling an implementation to control the subgroup size by allowing a varying subgroup size and a required size. The VK_EXT_subgroup_size_control extension specification explains:
This extension extends the subgroup support in Vulkan 1.1 to allow an implementation to expose a varying subgroup size. Previously Vulkan exposed a single subgroup size per physical device, with the expectation that implementations will behave as if all subgroups have the same size. Some implementations may: dispatch shaders with a varying subgroup size for different subgroups. As a result they could implicitly split a large subgroup into smaller subgroups or represent a small subgroup as a larger subgroup, some of whose invocations were inactive on launch.

To aid developers in understanding the performance characteristics of their programs, this extension exposes a minimum and maximum subgroup size that a physical device supports and a pipeline create flag to enable that pipeline to vary its subgroup size. If enabled, any code:SubgroupSize decorated variables in the SPIR-V shader modules provided to pipeline creation may: vary between the limits-min-subgroup-size,minimum and limits-max-subgroup-size,maximum subgroup sizes.

The other minor specification text corrections/clarifications for Vulkan 1.1.116 are outlined by this commit.
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