procedural-3d-engine/examples/computeheadless/computeheadless.cpp

/*
* Vulkan Example - Minimal headless compute example
*
* Copyright (C) 2017 by Sascha Willems - www.saschawillems.de
*
* This code is licensed under the MIT license (MIT) (http://opensource.org/licenses/MIT)
*/

// TODO: separate transfer queue (if not supported by compute queue) including buffer ownership transfer

#if defined(_WIN32)
#pragma comment(linker, "/subsystem:console")
#elif defined(VK_USE_PLATFORM_ANDROID_KHR)
#include <android/native_activity.h>
#include <android/asset_manager.h>
#include <android_native_app_glue.h>
#include <android/log.h>
#include "VulkanAndroid.h"
#endif

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <vector>
#include <iostream>
#include <algorithm>

#if defined(VK_USE_PLATFORM_MACOS_MVK)
#define VK_ENABLE_BETA_EXTENSIONS
#endif
#include <vulkan/vulkan.h>
#include "VulkanTools.h"

#if defined(VK_USE_PLATFORM_ANDROID_KHR)
android_app* androidapp;
#endif

#define DEBUG (!NDEBUG)

#define BUFFER_ELEMENTS 32

#if defined(VK_USE_PLATFORM_ANDROID_KHR)
#define LOG(...) ((void)__android_log_print(ANDROID_LOG_INFO, "vulkanExample", __VA_ARGS__))
#else
#define LOG(...) printf(__VA_ARGS__)
#endif

static VKAPI_ATTR VkBool32 VKAPI_CALL debugMessageCallback(
	VkDebugReportFlagsEXT flags,
	VkDebugReportObjectTypeEXT objectType,
	uint64_t object,
	size_t location,
	int32_t messageCode,
	const char* pLayerPrefix,
	const char* pMessage,
	void* pUserData)
{
	LOG("[VALIDATION]: %s - %s\n", pLayerPrefix, pMessage);
	return VK_FALSE;
}

class VulkanExample
{
public:
	VkInstance instance;
	VkPhysicalDevice physicalDevice;
	VkDevice device;
	uint32_t queueFamilyIndex;
	VkPipelineCache pipelineCache;
	VkQueue queue;
	VkCommandPool commandPool;
	VkCommandBuffer commandBuffer;
	VkFence fence;
	VkDescriptorPool descriptorPool;
	VkDescriptorSetLayout descriptorSetLayout;
	VkDescriptorSet descriptorSet;
	VkPipelineLayout pipelineLayout;
	VkPipeline pipeline;
	VkShaderModule shaderModule;

	VkDebugReportCallbackEXT debugReportCallback{};

	VkResult createBuffer(VkBufferUsageFlags usageFlags, VkMemoryPropertyFlags memoryPropertyFlags, VkBuffer *buffer, VkDeviceMemory *memory, VkDeviceSize size, void *data = nullptr)
	{
		// Create the buffer handle
		VkBufferCreateInfo bufferCreateInfo = vks::initializers::bufferCreateInfo(usageFlags, size);
		bufferCreateInfo.sharingMode = VK_SHARING_MODE_EXCLUSIVE;
		VK_CHECK_RESULT(vkCreateBuffer(device, &bufferCreateInfo, nullptr, buffer));

		// Create the memory backing up the buffer handle
		VkPhysicalDeviceMemoryProperties deviceMemoryProperties;
		vkGetPhysicalDeviceMemoryProperties(physicalDevice, &deviceMemoryProperties);
		VkMemoryRequirements memReqs;
		VkMemoryAllocateInfo memAlloc = vks::initializers::memoryAllocateInfo();
		vkGetBufferMemoryRequirements(device, *buffer, &memReqs);
		memAlloc.allocationSize = memReqs.size;
		// Find a memory type index that fits the properties of the buffer
		bool memTypeFound = false;
		for (uint32_t i = 0; i < deviceMemoryProperties.memoryTypeCount; i++) {
			if ((memReqs.memoryTypeBits & 1) == 1) {
				if ((deviceMemoryProperties.memoryTypes[i].propertyFlags & memoryPropertyFlags) == memoryPropertyFlags) {
					memAlloc.memoryTypeIndex = i;
					memTypeFound = true;
				}
			}
			memReqs.memoryTypeBits >>= 1;
		}
		assert(memTypeFound);
		VK_CHECK_RESULT(vkAllocateMemory(device, &memAlloc, nullptr, memory));

		if (data != nullptr) {
			void *mapped;
			VK_CHECK_RESULT(vkMapMemory(device, *memory, 0, size, 0, &mapped));
			memcpy(mapped, data, size);
			vkUnmapMemory(device, *memory);
		}

		VK_CHECK_RESULT(vkBindBufferMemory(device, *buffer, *memory, 0));

		return VK_SUCCESS;
	}

	VulkanExample()
	{
		LOG("Running headless compute example\n");

#if defined(VK_USE_PLATFORM_ANDROID_KHR)
		LOG("loading vulkan lib");
		vks::android::loadVulkanLibrary();
#endif

		VkApplicationInfo appInfo = {};
		appInfo.sType = VK_STRUCTURE_TYPE_APPLICATION_INFO;
		appInfo.pApplicationName = "Vulkan headless example";
		appInfo.pEngineName = "VulkanExample";
		appInfo.apiVersion = VK_API_VERSION_1_0;

		/*
			Vulkan instance creation (without surface extensions)
		*/
		VkInstanceCreateInfo instanceCreateInfo = {};
		instanceCreateInfo.sType = VK_STRUCTURE_TYPE_INSTANCE_CREATE_INFO;
		instanceCreateInfo.pApplicationInfo = &appInfo;

		uint32_t layerCount = 0;
#if defined(VK_USE_PLATFORM_ANDROID_KHR)
		const char* validationLayers[] = { "VK_LAYER_GOOGLE_threading",	"VK_LAYER_LUNARG_parameter_validation",	"VK_LAYER_LUNARG_object_tracker","VK_LAYER_LUNARG_core_validation",	"VK_LAYER_LUNARG_swapchain", "VK_LAYER_GOOGLE_unique_objects" };
		layerCount = 6;
#else
		const char* validationLayers[] = { "VK_LAYER_KHRONOS_validation" };
		layerCount = 1;
#endif
		std::vector<const char*> instanceExtensions = {};
#if DEBUG
		// Check if layers are available
		uint32_t instanceLayerCount;
		vkEnumerateInstanceLayerProperties(&instanceLayerCount, nullptr);
		std::vector<VkLayerProperties> instanceLayers(instanceLayerCount);
		vkEnumerateInstanceLayerProperties(&instanceLayerCount, instanceLayers.data());

		bool layersAvailable = true;
		for (auto layerName : validationLayers) {
			bool layerAvailable = false;
			for (auto instanceLayer : instanceLayers) {
				if (strcmp(instanceLayer.layerName, layerName) == 0) {
					layerAvailable = true;
					break;
				}
			}
			if (!layerAvailable) {
				layersAvailable = false;
				break;
			}
		}

		if (layersAvailable) {
			instanceExtensions.push_back(VK_EXT_DEBUG_REPORT_EXTENSION_NAME);
			instanceCreateInfo.ppEnabledLayerNames = validationLayers;
			instanceCreateInfo.enabledLayerCount = layerCount;
		}
#endif
#if defined(VK_USE_PLATFORM_MACOS_MVK)
		// SRS - When running on macOS with MoltenVK, enable VK_KHR_get_physical_device_properties2 (required by VK_KHR_portability_subset)
		instanceExtensions.push_back(VK_KHR_GET_PHYSICAL_DEVICE_PROPERTIES_2_EXTENSION_NAME);
#if defined(VK_KHR_portability_enumeration)
		// SRS - When running on macOS with MoltenVK and VK_KHR_portability_enumeration is defined and supported by the instance, enable the extension and the flag
		uint32_t instanceExtCount = 0;
		vkEnumerateInstanceExtensionProperties(nullptr, &instanceExtCount, nullptr);
		if (instanceExtCount > 0)
		{
			std::vector<VkExtensionProperties> extensions(instanceExtCount);
			if (vkEnumerateInstanceExtensionProperties(nullptr, &instanceExtCount, &extensions.front()) == VK_SUCCESS)
			{
				for (VkExtensionProperties extension : extensions)
				{
					if (strcmp(extension.extensionName, VK_KHR_PORTABILITY_ENUMERATION_EXTENSION_NAME) == 0)
					{
						instanceExtensions.push_back(VK_KHR_PORTABILITY_ENUMERATION_EXTENSION_NAME);
						instanceCreateInfo.flags = VK_INSTANCE_CREATE_ENUMERATE_PORTABILITY_BIT_KHR;
						break;
					}
				}
			}
		}
#endif
#endif
		instanceCreateInfo.enabledExtensionCount = (uint32_t)instanceExtensions.size();
		instanceCreateInfo.ppEnabledExtensionNames = instanceExtensions.data();
		VK_CHECK_RESULT(vkCreateInstance(&instanceCreateInfo, nullptr, &instance));

#if defined(VK_USE_PLATFORM_ANDROID_KHR)
		vks::android::loadVulkanFunctions(instance);
#endif
#if DEBUG
		if (layersAvailable) {
			VkDebugReportCallbackCreateInfoEXT debugReportCreateInfo = {};
			debugReportCreateInfo.sType = VK_STRUCTURE_TYPE_DEBUG_REPORT_CALLBACK_CREATE_INFO_EXT;
			debugReportCreateInfo.flags = VK_DEBUG_REPORT_ERROR_BIT_EXT | VK_DEBUG_REPORT_WARNING_BIT_EXT;
			debugReportCreateInfo.pfnCallback = (PFN_vkDebugReportCallbackEXT)debugMessageCallback;

			// We have to explicitly load this function.
			PFN_vkCreateDebugReportCallbackEXT vkCreateDebugReportCallbackEXT = reinterpret_cast<PFN_vkCreateDebugReportCallbackEXT>(vkGetInstanceProcAddr(instance, "vkCreateDebugReportCallbackEXT"));
			assert(vkCreateDebugReportCallbackEXT);
			VK_CHECK_RESULT(vkCreateDebugReportCallbackEXT(instance, &debugReportCreateInfo, nullptr, &debugReportCallback));
		}
#endif

		/*
			Vulkan device creation
		*/
		// Physical device (always use first)
		uint32_t deviceCount = 0;
		VK_CHECK_RESULT(vkEnumeratePhysicalDevices(instance, &deviceCount, nullptr));
		std::vector<VkPhysicalDevice> physicalDevices(deviceCount);
		VK_CHECK_RESULT(vkEnumeratePhysicalDevices(instance, &deviceCount, physicalDevices.data()));
		physicalDevice = physicalDevices[0];

		VkPhysicalDeviceProperties deviceProperties;
		vkGetPhysicalDeviceProperties(physicalDevice, &deviceProperties);
		LOG("GPU: %s\n", deviceProperties.deviceName);

		// Request a single compute queue
		const float defaultQueuePriority(0.0f);
		VkDeviceQueueCreateInfo queueCreateInfo = {};
		uint32_t queueFamilyCount;
		vkGetPhysicalDeviceQueueFamilyProperties(physicalDevice, &queueFamilyCount, nullptr);
		std::vector<VkQueueFamilyProperties> queueFamilyProperties(queueFamilyCount);
		vkGetPhysicalDeviceQueueFamilyProperties(physicalDevice, &queueFamilyCount, queueFamilyProperties.data());
		for (uint32_t i = 0; i < static_cast<uint32_t>(queueFamilyProperties.size()); i++) {
			if (queueFamilyProperties[i].queueFlags & VK_QUEUE_COMPUTE_BIT) {
				queueFamilyIndex = i;
				queueCreateInfo.sType = VK_STRUCTURE_TYPE_DEVICE_QUEUE_CREATE_INFO;
				queueCreateInfo.queueFamilyIndex = i;
				queueCreateInfo.queueCount = 1;
				queueCreateInfo.pQueuePriorities = &defaultQueuePriority;
				break;
			}
		}
		// Create logical device
		VkDeviceCreateInfo deviceCreateInfo = {};
		deviceCreateInfo.sType = VK_STRUCTURE_TYPE_DEVICE_CREATE_INFO;
		deviceCreateInfo.queueCreateInfoCount = 1;
		deviceCreateInfo.pQueueCreateInfos = &queueCreateInfo;
		std::vector<const char*> deviceExtensions = {};
#if defined(VK_USE_PLATFORM_MACOS_MVK) && defined(VK_KHR_portability_subset)
		// SRS - When running on macOS with MoltenVK and VK_KHR_portability_subset is defined and supported by the device, enable the extension
		uint32_t deviceExtCount = 0;
		vkEnumerateDeviceExtensionProperties(physicalDevice, nullptr, &deviceExtCount, nullptr);
		if (deviceExtCount > 0)
		{
			std::vector<VkExtensionProperties> extensions(deviceExtCount);
			if (vkEnumerateDeviceExtensionProperties(physicalDevice, nullptr, &deviceExtCount, &extensions.front()) == VK_SUCCESS)
			{
				for (VkExtensionProperties extension : extensions)
				{
					if (strcmp(extension.extensionName, VK_KHR_PORTABILITY_SUBSET_EXTENSION_NAME) == 0)
					{
						deviceExtensions.push_back(VK_KHR_PORTABILITY_SUBSET_EXTENSION_NAME);
						break;
					}
				}
			}
		}
#endif
		deviceCreateInfo.enabledExtensionCount = (uint32_t)deviceExtensions.size();
		deviceCreateInfo.ppEnabledExtensionNames = deviceExtensions.data();
		VK_CHECK_RESULT(vkCreateDevice(physicalDevice, &deviceCreateInfo, nullptr, &device));

		// Get a compute queue
		vkGetDeviceQueue(device, queueFamilyIndex, 0, &queue);

		// Compute command pool
		VkCommandPoolCreateInfo cmdPoolInfo = {};
		cmdPoolInfo.sType = VK_STRUCTURE_TYPE_COMMAND_POOL_CREATE_INFO;
		cmdPoolInfo.queueFamilyIndex = queueFamilyIndex;
		cmdPoolInfo.flags = VK_COMMAND_POOL_CREATE_RESET_COMMAND_BUFFER_BIT;
		VK_CHECK_RESULT(vkCreateCommandPool(device, &cmdPoolInfo, nullptr, &commandPool));

		/*
			Prepare storage buffers
		*/
		std::vector<uint32_t> computeInput(BUFFER_ELEMENTS);
		std::vector<uint32_t> computeOutput(BUFFER_ELEMENTS);

		// Fill input data
		uint32_t n = 0;
		std::generate(computeInput.begin(), computeInput.end(), [&n] { return n++; });

		const VkDeviceSize bufferSize = BUFFER_ELEMENTS * sizeof(uint32_t);

		VkBuffer deviceBuffer, hostBuffer;
		VkDeviceMemory deviceMemory, hostMemory;

		// Copy input data to VRAM using a staging buffer
		{
			createBuffer(
				VK_BUFFER_USAGE_TRANSFER_SRC_BIT | VK_BUFFER_USAGE_TRANSFER_DST_BIT,
				VK_MEMORY_PROPERTY_HOST_VISIBLE_BIT,
				&hostBuffer,
				&hostMemory,
				bufferSize,
				computeInput.data());

			// Flush writes to host visible buffer
			void* mapped;
			vkMapMemory(device, hostMemory, 0, VK_WHOLE_SIZE, 0, &mapped);
			VkMappedMemoryRange mappedRange = vks::initializers::mappedMemoryRange();
			mappedRange.memory = hostMemory;
			mappedRange.offset = 0;
			mappedRange.size = VK_WHOLE_SIZE;
			vkFlushMappedMemoryRanges(device, 1, &mappedRange);
			vkUnmapMemory(device, hostMemory);

			createBuffer(
				VK_BUFFER_USAGE_STORAGE_BUFFER_BIT | VK_BUFFER_USAGE_TRANSFER_SRC_BIT | VK_BUFFER_USAGE_TRANSFER_DST_BIT,
				VK_MEMORY_PROPERTY_DEVICE_LOCAL_BIT,
				&deviceBuffer,
				&deviceMemory,
				bufferSize);

			// Copy to staging buffer
			VkCommandBufferAllocateInfo cmdBufAllocateInfo = vks::initializers::commandBufferAllocateInfo(commandPool, VK_COMMAND_BUFFER_LEVEL_PRIMARY, 1);
			VkCommandBuffer copyCmd;
			VK_CHECK_RESULT(vkAllocateCommandBuffers(device, &cmdBufAllocateInfo, &copyCmd));
			VkCommandBufferBeginInfo cmdBufInfo = vks::initializers::commandBufferBeginInfo();
			VK_CHECK_RESULT(vkBeginCommandBuffer(copyCmd, &cmdBufInfo));

			VkBufferCopy copyRegion = {};
			copyRegion.size = bufferSize;
			vkCmdCopyBuffer(copyCmd, hostBuffer, deviceBuffer, 1, &copyRegion);
			VK_CHECK_RESULT(vkEndCommandBuffer(copyCmd));

			VkSubmitInfo submitInfo = vks::initializers::submitInfo();
			submitInfo.commandBufferCount = 1;
			submitInfo.pCommandBuffers = &copyCmd;
			VkFenceCreateInfo fenceInfo = vks::initializers::fenceCreateInfo(VK_FLAGS_NONE);
			VkFence fence;
			VK_CHECK_RESULT(vkCreateFence(device, &fenceInfo, nullptr, &fence));

			// Submit to the queue
			VK_CHECK_RESULT(vkQueueSubmit(queue, 1, &submitInfo, fence));
			VK_CHECK_RESULT(vkWaitForFences(device, 1, &fence, VK_TRUE, UINT64_MAX));

			vkDestroyFence(device, fence, nullptr);
			vkFreeCommandBuffers(device, commandPool, 1, &copyCmd);
		}

		/*
			Prepare compute pipeline
		*/
		{
			std::vector<VkDescriptorPoolSize> poolSizes = {
				vks::initializers::descriptorPoolSize(VK_DESCRIPTOR_TYPE_STORAGE_BUFFER, 1),
			};

			VkDescriptorPoolCreateInfo descriptorPoolInfo =
				vks::initializers::descriptorPoolCreateInfo(static_cast<uint32_t>(poolSizes.size()), poolSizes.data(), 1);
			VK_CHECK_RESULT(vkCreateDescriptorPool(device, &descriptorPoolInfo, nullptr, &descriptorPool));

			std::vector<VkDescriptorSetLayoutBinding> setLayoutBindings = {
				vks::initializers::descriptorSetLayoutBinding(VK_DESCRIPTOR_TYPE_STORAGE_BUFFER, VK_SHADER_STAGE_COMPUTE_BIT, 0),
			};
			VkDescriptorSetLayoutCreateInfo descriptorLayout =
				vks::initializers::descriptorSetLayoutCreateInfo(setLayoutBindings);
			VK_CHECK_RESULT(vkCreateDescriptorSetLayout(device, &descriptorLayout, nullptr, &descriptorSetLayout));

			VkPipelineLayoutCreateInfo pipelineLayoutCreateInfo =
				vks::initializers::pipelineLayoutCreateInfo(&descriptorSetLayout, 1);
			VK_CHECK_RESULT(vkCreatePipelineLayout(device, &pipelineLayoutCreateInfo, nullptr, &pipelineLayout));

			VkDescriptorSetAllocateInfo allocInfo =
				vks::initializers::descriptorSetAllocateInfo(descriptorPool, &descriptorSetLayout, 1);
			VK_CHECK_RESULT(vkAllocateDescriptorSets(device, &allocInfo, &descriptorSet));

			VkDescriptorBufferInfo bufferDescriptor = { deviceBuffer, 0, VK_WHOLE_SIZE };
			std::vector<VkWriteDescriptorSet> computeWriteDescriptorSets = {
				vks::initializers::writeDescriptorSet(descriptorSet, VK_DESCRIPTOR_TYPE_STORAGE_BUFFER, 0, &bufferDescriptor),
			};
			vkUpdateDescriptorSets(device, static_cast<uint32_t>(computeWriteDescriptorSets.size()), computeWriteDescriptorSets.data(), 0, NULL);

			VkPipelineCacheCreateInfo pipelineCacheCreateInfo = {};
			pipelineCacheCreateInfo.sType = VK_STRUCTURE_TYPE_PIPELINE_CACHE_CREATE_INFO;
			VK_CHECK_RESULT(vkCreatePipelineCache(device, &pipelineCacheCreateInfo, nullptr, &pipelineCache));

			// Create pipeline
			VkComputePipelineCreateInfo computePipelineCreateInfo = vks::initializers::computePipelineCreateInfo(pipelineLayout, 0);

			// Pass SSBO size via specialization constant
			struct SpecializationData {
				uint32_t BUFFER_ELEMENT_COUNT = BUFFER_ELEMENTS;
			} specializationData;
			VkSpecializationMapEntry specializationMapEntry = vks::initializers::specializationMapEntry(0, 0, sizeof(uint32_t));
			VkSpecializationInfo specializationInfo = vks::initializers::specializationInfo(1, &specializationMapEntry, sizeof(SpecializationData), &specializationData);

			// TODO: There is no command line arguments parsing (nor Android settings) for this
			// example, so we have no way of picking between GLSL or HLSL shaders.
			// Hard-code to glsl for now.
			const std::string shadersPath = getAssetPath() + "shaders/glsl/computeheadless/";

			VkPipelineShaderStageCreateInfo shaderStage = {};
			shaderStage.sType = VK_STRUCTURE_TYPE_PIPELINE_SHADER_STAGE_CREATE_INFO;
			shaderStage.stage = VK_SHADER_STAGE_COMPUTE_BIT;
#if defined(VK_USE_PLATFORM_ANDROID_KHR)
			shaderStage.module = vks::tools::loadShader(androidapp->activity->assetManager, (shadersPath + "headless.comp.spv").c_str(), device);
#else
			shaderStage.module = vks::tools::loadShader((shadersPath + "headless.comp.spv").c_str(), device);
#endif
			shaderStage.pName = "main";
			shaderStage.pSpecializationInfo = &specializationInfo;
			shaderModule = shaderStage.module;

			assert(shaderStage.module != VK_NULL_HANDLE);
			computePipelineCreateInfo.stage = shaderStage;
			VK_CHECK_RESULT(vkCreateComputePipelines(device, pipelineCache, 1, &computePipelineCreateInfo, nullptr, &pipeline));

			// Create a command buffer for compute operations
			VkCommandBufferAllocateInfo cmdBufAllocateInfo =
				vks::initializers::commandBufferAllocateInfo(commandPool, VK_COMMAND_BUFFER_LEVEL_PRIMARY, 1);
			VK_CHECK_RESULT(vkAllocateCommandBuffers(device, &cmdBufAllocateInfo, &commandBuffer));

			// Fence for compute CB sync
			VkFenceCreateInfo fenceCreateInfo = vks::initializers::fenceCreateInfo(VK_FENCE_CREATE_SIGNALED_BIT);
			VK_CHECK_RESULT(vkCreateFence(device, &fenceCreateInfo, nullptr, &fence));
		}

		/*
			Command buffer creation (for compute work submission)
		*/
		{
			VkCommandBufferBeginInfo cmdBufInfo = vks::initializers::commandBufferBeginInfo();

			VK_CHECK_RESULT(vkBeginCommandBuffer(commandBuffer, &cmdBufInfo));

			// Barrier to ensure that input buffer transfer is finished before compute shader reads from it
			VkBufferMemoryBarrier bufferBarrier = vks::initializers::bufferMemoryBarrier();
			bufferBarrier.buffer = deviceBuffer;
			bufferBarrier.size = VK_WHOLE_SIZE;
			bufferBarrier.srcAccessMask = VK_ACCESS_HOST_WRITE_BIT;
			bufferBarrier.dstAccessMask = VK_ACCESS_SHADER_READ_BIT;
			bufferBarrier.srcQueueFamilyIndex = VK_QUEUE_FAMILY_IGNORED;
			bufferBarrier.dstQueueFamilyIndex = VK_QUEUE_FAMILY_IGNORED;

			vkCmdPipelineBarrier(
				commandBuffer,
				VK_PIPELINE_STAGE_HOST_BIT,
				VK_PIPELINE_STAGE_COMPUTE_SHADER_BIT,
				VK_FLAGS_NONE,
				0, nullptr,
				1, &bufferBarrier,
				0, nullptr);

			vkCmdBindPipeline(commandBuffer, VK_PIPELINE_BIND_POINT_COMPUTE, pipeline);
			vkCmdBindDescriptorSets(commandBuffer, VK_PIPELINE_BIND_POINT_COMPUTE, pipelineLayout, 0, 1, &descriptorSet, 0, 0);

			vkCmdDispatch(commandBuffer, BUFFER_ELEMENTS, 1, 1);

			// Barrier to ensure that shader writes are finished before buffer is read back from GPU
			bufferBarrier.srcAccessMask = VK_ACCESS_SHADER_WRITE_BIT;
			bufferBarrier.dstAccessMask = VK_ACCESS_TRANSFER_READ_BIT;
			bufferBarrier.buffer = deviceBuffer;
			bufferBarrier.size = VK_WHOLE_SIZE;
			bufferBarrier.srcQueueFamilyIndex = VK_QUEUE_FAMILY_IGNORED;
			bufferBarrier.dstQueueFamilyIndex = VK_QUEUE_FAMILY_IGNORED;

			vkCmdPipelineBarrier(
				commandBuffer,
				VK_PIPELINE_STAGE_COMPUTE_SHADER_BIT,
				VK_PIPELINE_STAGE_TRANSFER_BIT,
				VK_FLAGS_NONE,
				0, nullptr,
				1, &bufferBarrier,
				0, nullptr);

			// Read back to host visible buffer
			VkBufferCopy copyRegion = {};
			copyRegion.size = bufferSize;
			vkCmdCopyBuffer(commandBuffer, deviceBuffer, hostBuffer, 1, &copyRegion);

			// Barrier to ensure that buffer copy is finished before host reading from it
			bufferBarrier.srcAccessMask = VK_ACCESS_TRANSFER_WRITE_BIT;
			bufferBarrier.dstAccessMask = VK_ACCESS_HOST_READ_BIT;
			bufferBarrier.buffer = hostBuffer;
			bufferBarrier.size = VK_WHOLE_SIZE;
			bufferBarrier.srcQueueFamilyIndex = VK_QUEUE_FAMILY_IGNORED;
			bufferBarrier.dstQueueFamilyIndex = VK_QUEUE_FAMILY_IGNORED;

			vkCmdPipelineBarrier(
				commandBuffer,
				VK_PIPELINE_STAGE_TRANSFER_BIT,
				VK_PIPELINE_STAGE_HOST_BIT,
				VK_FLAGS_NONE,
				0, nullptr,
				1, &bufferBarrier,
				0, nullptr);

			VK_CHECK_RESULT(vkEndCommandBuffer(commandBuffer));

			// Submit compute work
			vkResetFences(device, 1, &fence);
			const VkPipelineStageFlags waitStageMask = VK_PIPELINE_STAGE_TRANSFER_BIT;
			VkSubmitInfo computeSubmitInfo = vks::initializers::submitInfo();
			computeSubmitInfo.pWaitDstStageMask = &waitStageMask;
			computeSubmitInfo.commandBufferCount = 1;
			computeSubmitInfo.pCommandBuffers = &commandBuffer;
			VK_CHECK_RESULT(vkQueueSubmit(queue, 1, &computeSubmitInfo, fence));
			VK_CHECK_RESULT(vkWaitForFences(device, 1, &fence, VK_TRUE, UINT64_MAX));

			// Make device writes visible to the host
			void *mapped;
			vkMapMemory(device, hostMemory, 0, VK_WHOLE_SIZE, 0, &mapped);
			VkMappedMemoryRange mappedRange = vks::initializers::mappedMemoryRange();
			mappedRange.memory = hostMemory;
			mappedRange.offset = 0;
			mappedRange.size = VK_WHOLE_SIZE;
			vkInvalidateMappedMemoryRanges(device, 1, &mappedRange);

			// Copy to output
			memcpy(computeOutput.data(), mapped, bufferSize);
			vkUnmapMemory(device, hostMemory);
		}

		vkQueueWaitIdle(queue);

		// Output buffer contents
		LOG("Compute input:\n");
		for (auto v : computeInput) {
			LOG("%d \t", v);
		}
		std::cout << std::endl;

		LOG("Compute output:\n");
		for (auto v : computeOutput) {
			LOG("%d \t", v);
		}
		std::cout << std::endl;

		// Clean up
		vkDestroyBuffer(device, deviceBuffer, nullptr);
		vkFreeMemory(device, deviceMemory, nullptr);
		vkDestroyBuffer(device, hostBuffer, nullptr);
		vkFreeMemory(device, hostMemory, nullptr);
	}

	~VulkanExample()
	{
		vkDestroyPipelineLayout(device, pipelineLayout, nullptr);
		vkDestroyDescriptorSetLayout(device, descriptorSetLayout, nullptr);
		vkDestroyDescriptorPool(device, descriptorPool, nullptr);
		vkDestroyPipeline(device, pipeline, nullptr);
		vkDestroyPipelineCache(device, pipelineCache, nullptr);
		vkDestroyFence(device, fence, nullptr);
		vkDestroyCommandPool(device, commandPool, nullptr);
		vkDestroyShaderModule(device, shaderModule, nullptr);
		vkDestroyDevice(device, nullptr);
#if DEBUG
		if (debugReportCallback) {
			PFN_vkDestroyDebugReportCallbackEXT vkDestroyDebugReportCallback = reinterpret_cast<PFN_vkDestroyDebugReportCallbackEXT>(vkGetInstanceProcAddr(instance, "vkDestroyDebugReportCallbackEXT"));
			assert(vkDestroyDebugReportCallback);
			vkDestroyDebugReportCallback(instance, debugReportCallback, nullptr);
		}
#endif
		vkDestroyInstance(instance, nullptr);
	}
};

#if defined(VK_USE_PLATFORM_ANDROID_KHR)
void handleAppCommand(android_app * app, int32_t cmd) {
	if (cmd == APP_CMD_INIT_WINDOW) {
		VulkanExample *vulkanExample = new VulkanExample();
		delete(vulkanExample);
		ANativeActivity_finish(app->activity);
	}
}
void android_main(android_app* state) {
	androidapp = state;
	androidapp->onAppCmd = handleAppCommand;
	int ident, events;
	struct android_poll_source* source;
	while ((ident = ALooper_pollAll(-1, NULL, &events, (void**)&source)) >= 0) {
		if (source != NULL)	{
			source->process(androidapp, source);
		}
		if (androidapp->destroyRequested != 0) {
			break;
		}
	}
}
#else
int main() {
	VulkanExample *vulkanExample = new VulkanExample();
	std::cout << "Finished. Press enter to terminate...";
	getchar();
	delete(vulkanExample);
	return 0;
}
#endif