Name

VK_KHR_shader_fma - device extension

VK_KHR_shader_fma

Name String

VK_KHR_shader_fma

Extension Type

Device extension

Registered Extension Number

580

Revision

1

Ratification Status

Ratified

Extension and Version Dependencies

VK_KHR_get_physical_device_properties2 or Vulkan Version 1.1

SPIR-V Dependencies

• SPV_KHR_fma

Contact

• Graeme Leese @gnl21%0A*Here describe the issue or question you have about the VK_KHR_shader_fma extension*

Extension Proposal

VK_KHR_shader_fma

Other Extension Metadata

Last Modified Date

2025-06-10

Contributors

• Graeme Leese, Broadcom

Description

This extension allows applications to use the SPV_KHR_fma extension to obtain correctly-rounded results for fused-multiply add (fma) operations.

Fused-multiply add is a building block of many high-precision numerical functions. It provides better accuracy than separate operations, because of the removal of the intermediate rounding step, and often costs less than the pair of separate operations.

Vulkan currently exposes an fma primitive that can give the reduced cost, but it is not guaranteed to be a fused operation, so the accuracy cannot be relied on. For applications which require the high accuracy, therefore, the operation must be emulated or the algorithm changed so as not to require fma. This is often vastly more costly, even though fma is supported in much of the underlying hardware.

New Structures

• Extending PhysicalDeviceFeatures2, DeviceCreateInfo:

  • PhysicalDeviceShaderFmaFeaturesKHR

New Enum Constants

• KHR_SHADER_FMA_EXTENSION_NAME

• KHR_SHADER_FMA_SPEC_VERSION

• Extending StructureType:

  • STRUCTURE_TYPE_PHYSICAL_DEVICE_SHADER_FMA_FEATURES_KHR

Version History

• Revision 1, 2025-06-10 (Graeme Leese)

  • Initial draft

See Also

No cross-references are available

Document Notes

For more information, see the Vulkan Specification.

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