# SubgroupLtMask(3) Manual Page

## Name

SubgroupLtMask - Mask of shader invocations in a subgroup with a lower subgroup local invocation ID

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## Description

`SubgroupLtMask`

  Decorating a variable with the `SubgroupLtMask` builtin decoration will make that variable contain the subgroup mask of the current subgroup invocation. The bits corresponding to the invocations less than `SubgroupLocalInvocationId` are set in the variable decorated with `SubgroupLtMask`. All other bits are set to zero.

  `SubgroupLtMaskKHR` is an alias of `SubgroupLtMask`.

Valid Usage

- VUID-SubgroupLtMask-SubgroupLtMask-04378
  The variable decorated with `SubgroupLtMask` must be declared using the `Input` `Storage` `Class`

- VUID-SubgroupLtMask-SubgroupLtMask-04379
  The variable decorated with `SubgroupLtMask` must be declared as a four-component vector of 32-bit integer values

## See Also

No cross-references are available

## Document Notes

For more information, see the Vulkan Specification

This page is extracted from the Vulkan Specification. Fixes and changes should be made to the Specification, not directly.

## Copyright

Copyright 2014-2025 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0