Class EXTShaderSubgroupVote
 java.lang.Object

 org.lwjgl.vulkan.EXTShaderSubgroupVote

public final class EXTShaderSubgroupVote extends java.lang.Object
This extension adds support for the following SPIRV extension in Vulkan:SPV_KHR_subgroup_vote
This extension provides new SPIRV instructions:
OpSubgroupAllKHR
,OpSubgroupAnyKHR
, andOpSubgroupAllEqualKHR
.
to compute the composite of a set of boolean conditions across a group of shader invocations that are running concurrently (a subgroup). These composite results may be used to execute shaders more efficiently on a
VkPhysicalDevice
.When using GLSL sourcebased shader languages, the following shader functions from GL_ARB_shader_group_vote can map to these SPIRV instructions:
anyInvocationARB
() →OpSubgroupAnyKHR
,allInvocationsARB
() →OpSubgroupAllKHR
, andallInvocationsEqualARB
() →OpSubgroupAllEqualKHR
.
The subgroup across which the boolean conditions are evaluated is implementationdependent, and this extension provides no guarantee over how individual shader invocations are assigned to subgroups. In particular, a subgroup has no necessary relationship with the compute shader local workgroup  any pair of shader invocations in a compute local workgroup may execute in different subgroups as used by these instructions.
Compute shaders operate on an explicitly specified group of threads (a local workgroup), but many implementations will also group noncompute shader invocations and execute them concurrently. When executing code like
if (condition) { result = do_fast_path(); } else { result = do_general_path(); }
where
condition
diverges between invocations, an implementation might first executedo_fast_path
() for the invocations wherecondition
is true and leave the other invocations dormant. Oncedo_fast_path
() returns, it might calldo_general_path
() for invocations wherecondition
isfalse
and leave the other invocations dormant. In this case, the shader executes both the fast and the general path and might be better off just using the general path for all invocations.This extension provides the ability to avoid divergent execution by evaluating a condition across an entire subgroup using code like:
if (allInvocationsARB(condition)) { result = do_fast_path(); } else { result = do_general_path(); }
The builtin function
allInvocationsARB
() will return the same value for all invocations in the group, so the group will either executedo_fast_path
() ordo_general_path
(), but never both. For example, shader code might want to evaluate a complex function iteratively by starting with an approximation of the result and then refining the approximation. Some input values may require a small number of iterations to generate an accurate result (do_fast_path
) while others require a larger number (do_general_path
). In another example, shader code might want to evaluate a complex function (do_general_path
) that can be greatly simplified when assuming a specific value for one of its inputs (do_fast_path
). Name String
VK_EXT_shader_subgroup_vote
 Extension Type
 Device extension
 Registered Extension Number
 66
 Revision
 1
 Extension and Version Dependencies
 Requires Vulkan 1.0
 Contact
 Daniel Koch dgkoch
 Last Modified Date
 20161128
 IP Status
 No known IP claims.
 Interactions and External Dependencies
 This extension requires the
SPV_KHR_subgroup_vote
SPIRV extension.  This extension requires the
GL_ARB_shader_group_vote
extension for GLSL source languages.
 This extension requires the
 Contributors
 Neil Henning, Codeplay
 Daniel Koch, NVIDIA Corporation


Field Summary
Fields Modifier and Type Field Description static java.lang.String
VK_EXT_SHADER_SUBGROUP_VOTE_EXTENSION_NAME
The extension name.static int
VK_EXT_SHADER_SUBGROUP_VOTE_SPEC_VERSION
The extension specification version.



Field Detail

VK_EXT_SHADER_SUBGROUP_VOTE_SPEC_VERSION
public static final int VK_EXT_SHADER_SUBGROUP_VOTE_SPEC_VERSION
The extension specification version. See Also:
 Constant Field Values

VK_EXT_SHADER_SUBGROUP_VOTE_EXTENSION_NAME
public static final java.lang.String VK_EXT_SHADER_SUBGROUP_VOTE_EXTENSION_NAME
The extension name. See Also:
 Constant Field Values

