Safe Haskell | None |
---|---|
Language | Haskell2010 |
Name
VK_EXT_shader_subgroup_vote - device extension
VK_EXT_shader_subgroup_vote
- 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
- Deprecation state
- Deprecated by Vulkan 1.1
- Contact
Other Extension Metadata
- Last Modified Date
- 2016-11-28
- IP Status
- No known IP claims.
- Interactions and External Dependencies
- This extension requires SPV_KHR_subgroup_vote
- This extension provides API support for GL_ARB_shader_group_vote
- Contributors
- Neil Henning, Codeplay
- Daniel Koch, NVIDIA Corporation
Description
This extension adds support for the following SPIR-V extension in Vulkan:
SPV_KHR_subgroup_vote
This extension provides new SPIR-V 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 PhysicalDevice
.
When using GLSL source-based shader languages, the following shader functions from GL_ARB_shader_group_vote can map to these SPIR-V instructions:
anyInvocationARB
() →OpSubgroupAnyKHR
,allInvocationsARB
() →OpSubgroupAllKHR
, andallInvocationsEqualARB
() →OpSubgroupAllEqualKHR
.
The subgroup across which the boolean conditions are evaluated is implementation-dependent, 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 non-compute 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 execute do_fast_path
() for the invocations where condition
is
true and leave the other invocations dormant. Once do_fast_path
()
returns, it might call do_general_path
() for invocations where
condition
is false
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 built-in function allInvocationsARB
() will return the same value
for all invocations in the group, so the group will either execute
do_fast_path
() or do_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
).
Deprecated by Vulkan 1.1
All functionality in this extension is superseded by the core Vulkan 1.1 subgroup operations.
New Enum Constants
New SPIR-V Capabilities
Version History
Revision 1, 2016-11-28 (Daniel Koch)
- Initial draft
See Also
No cross-references are available
Document Notes
For more information, see the Vulkan Specification
This page is a generated document. Fixes and changes should be made to the generator scripts, not directly.
Documentation
type EXT_SHADER_SUBGROUP_VOTE_SPEC_VERSION = 1 Source #
pattern EXT_SHADER_SUBGROUP_VOTE_SPEC_VERSION :: forall a. Integral a => a Source #
type EXT_SHADER_SUBGROUP_VOTE_EXTENSION_NAME = "VK_EXT_shader_subgroup_vote" Source #
pattern EXT_SHADER_SUBGROUP_VOTE_EXTENSION_NAME :: forall a. (Eq a, IsString a) => a Source #