5. Vulkan Compute (1.3 / 1.4) and the ash Crate

5.1 Latest Stable Versions

• Vulkan Specification: Vulkan 1.4 (with full Vulkan 1.3 compatibility)
• ash: 0.38.0+1.3.281

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5.2 Vulkan (1.2 - 1.4) & ash (0.37 - 0.38.0) Changelog

A. Promotion of VK_EXT_subgroup_size_control and VK_KHR_synchronization2 to Vulkan 1.3 Core

• What changed:
• VK_EXT_subgroup_size_control was promoted to Vulkan 1.3 core inside vk::PhysicalDeviceVulkan13Features (subgroup_size_control and compute_full_subgroups) and vk::PhysicalDeviceVulkan13Properties (min_subgroup_size, max_subgroup_size, required_subgroup_size_stages).
• VkPipelineShaderStageRequiredSubgroupSizeCreateInfoEXT was promoted to the core type vk::PipelineShaderStageRequiredSubgroupSizeCreateInfo without the EXT suffix.
• VK_KHR_synchronization2 (vkCmdPipelineBarrier2, VkMemoryBarrier2, VkDependencyInfo) was promoted to Vulkan 1.3 core.

B. Specification Validation Rule VUID-VkPipelineShaderStageCreateInfo-pNext-02756

• What changed: Under the Vulkan 1.3 and 1.4 specifications, chaining vk::PipelineShaderStageRequiredSubgroupSizeCreateInfo with required_subgroup_size = 32 onto a compute pipeline stage is only valid when all three conditions hold simultaneously:
• features13.subgroup_size_control == vk::TRUE
• props13.min_subgroup_size <= 32 && props13.max_subgroup_size >= 32
• props13.required_subgroup_size_stages contains vk::ShaderStageFlags::COMPUTE
• Why it matters: Checking features13.subgroup_size_control == vk::TRUE alone without inspecting PhysicalDeviceVulkan13Properties can cause pipeline creation failure (VK_ERROR_INITIALIZATION_FAILED or validation errors) on GPUs that support subgroup_size_control but have min_subgroup_size = 64 or do not permit subgroup size overrides in the COMPUTE stage.

C. Dynamic Instance Version Negotiation (Vulkan 1.4 vs 1.3)

• What changed: On modern drivers supporting Vulkan 1.4, entry.try_enumerate_instance_version() returns a runtime loader version >= 1.4.0.

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5.3 Adaptations in LuminaMoon Source Code

1. Dynamic 1.4.0 / 1.3.0 API Negotiation and Subgroup Property Validation

• File: optimizer/crates/luminav-vulkan/src/context.rs
• Implementation:

  let supported_instance_version = unsafe {
      entry
          .try_enumerate_instance_version()?
          .unwrap_or(vk::API_VERSION_1_3)
  };
  let target_api_version = if supported_instance_version >= vk::make_api_version(0, 1, 4, 0) {
      vk::make_api_version(0, 1, 4, 0)
  } else {
      vk::make_api_version(0, 1, 3, 0)
  };
  

  And Vulkan 1.3 device property verification for Wave32 mode:

  let mut props13 = vk::PhysicalDeviceVulkan13Properties::default();
  let mut props2 = vk::PhysicalDeviceProperties2::default().push_next(&mut props13);
  unsafe { instance.get_physical_device_properties2(pdevice, &mut props2) };
  
  let wave32_supported = features13.subgroup_size_control == vk::TRUE
      && props13.min_subgroup_size <= 32
      && props13.max_subgroup_size >= 32
      && props13
          .required_subgroup_size_stages
          .contains(vk::ShaderStageFlags::COMPUTE);
  

2. Clean Drop Implementation on VulkanContext

• File: optimizer/crates/luminav-vulkan/src/context.rs
• Implementation: Streamlined logical device destruction (self.device.destroy_device(None)) after device_wait_idle() without redundant Arc::get_mut branching.