kmeans_gpu.cpp

 
#include "internal/kmeans_gpu.h"
 
#include "img2num.h"
#include "internal/cielab.h"
#include "internal/gpu.h"
#include "internal/Image.h"
#include "internal/LABAPixel.h"
#include "internal/PixelConverters.h"
#include "internal/RGBAPixel.h"
 
#include <algorithm>
#include <cmath>
#include <cstddef>
#include <cstdint>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <functional>
#include <limits>
#include <numeric>
#include <random>
#include <type_traits> // Required for std::is_same_v
#include <vector>
 
static constexpr uint8_t COLOR_SPACE_OPTION_CIELAB {0};
static constexpr uint8_t COLOR_SPACE_OPTION_RGB {1};
 
#ifdef _MSC_VER
#pragma pack(push, 1)
#endif
struct Params {
    uint32_t numPoints;
    uint32_t numCentroids;
    uint32_t pad[2];
}
#ifndef _MSC_VER
__attribute__((packed))
#endif
;
#ifdef _MSC_VER
#pragma pack(pop)
#endif
 
#ifdef _MSC_VER
#pragma pack(push, 1)
#endif
struct ClusterAccumulator {
    int32_t sumR;
    int32_t sumG;
    int32_t sumB;
    uint32_t count;
}
#ifndef _MSC_VER
__attribute__((packed))
#endif
;
#ifdef _MSC_VER
#pragma pack(pop)
#endif
 
#ifdef _MSC_VER
#pragma pack(push, 1)
#endif
struct CentroidParams {
    float r, g, b, a;
    uint32_t width;
    uint32_t pad[3]; // Padding to align to 16 bytes
}
#ifndef _MSC_VER
__attribute__((packed))
#endif
;
#ifdef _MSC_VER
#pragma pack(pop)
#endif
 
// The K-Means++ Initialization Function
template <typename PixelT>
void kMeansPlusPlusInitGpu(
    const ImageLib::Image<PixelT>& pixels, ImageLib::Image<PixelT>& out_centroids, int k,
    const uint8_t color_space
) {
    if (k <= 0)
        return;
 
    size_t width = pixels.getWidth();
    size_t height = pixels.getHeight();
    size_t num_pixels = width * height;
 
    std::vector<PixelT> centroids;
 
    // --- WEBGPU SETUP START ---
    // (Assuming 'device' and 'queue' are globally available or passed in)
    // 1. Upload Image Texture
    wgpu::TextureDescriptor texDesc = {};
    texDesc.size = {static_cast<uint32_t>(width), static_cast<uint32_t>(height), 1};
    texDesc.format = wgpu::TextureFormat::RGBA32Float;
    texDesc.usage = wgpu::TextureUsage::TextureBinding | wgpu::TextureUsage::CopyDst;
    texDesc.label = "inputTextureInit";
    wgpu::Texture inputTexture = GPU::getClassInstance().get_device().CreateTexture(&texDesc);
 
    // Upload pixel data (Normalization to 0.0-1.0 assumed)
    std::vector<float> gpu_pixels;
    gpu_pixels.reserve(num_pixels * 4);
 
    for (int i = 0; i < num_pixels; i++) {
        PixelT p = pixels[i];
        if constexpr (std::is_same_v<PixelT, ImageLib::LABAPixel<float>>) {
            gpu_pixels.push_back(p.l / 255.0f);
            gpu_pixels.push_back(p.a / 255.0f);
            gpu_pixels.push_back(p.b / 255.0f);
            gpu_pixels.push_back(p.alpha / 255.0f);
        } else {
            gpu_pixels.push_back(p.red / 255.0f);
            gpu_pixels.push_back(p.green / 255.0f);
            gpu_pixels.push_back(p.blue / 255.0f);
            gpu_pixels.push_back(p.alpha / 255.0f);
        }
    }
 
    wgpu::TexelCopyTextureInfo texDst = {};
    texDst.texture = inputTexture;
    wgpu::TexelCopyBufferLayout texLayout = {};
    texLayout.bytesPerRow = width * 16;
    texLayout.rowsPerImage = height;
    GPU::getClassInstance().get_queue().WriteTexture(
        &texDst, gpu_pixels.data(), gpu_pixels.size() * 4, &texLayout, &texDesc.size
    );
 
    // 2. Create MinDist Buffer (Storage)
    // Initialize with FLT_MAX so the first centroid overwrites everything
    std::vector<float> initial_dists(num_pixels, std::numeric_limits<float>::max());
 
    wgpu::BufferDescriptor distDesc = {};
    distDesc.size = num_pixels * sizeof(float);
    distDesc.usage =
        wgpu::BufferUsage::Storage | wgpu::BufferUsage::CopySrc | wgpu::BufferUsage::CopyDst;
    wgpu::Buffer minDistBuffer = GPU::getClassInstance().get_device().CreateBuffer(&distDesc);
    GPU::getClassInstance().get_queue().WriteBuffer(
        minDistBuffer, 0, initial_dists.data(), distDesc.size
    );
 
    // 3. Create Uniform Buffer (For passing new centroid color)
 
    wgpu::BufferDescriptor uniDesc = {};
    uniDesc.size = sizeof(CentroidParams);
    uniDesc.usage = wgpu::BufferUsage::Uniform | wgpu::BufferUsage::CopyDst;
    wgpu::Buffer paramBuffer = GPU::getClassInstance().get_device().CreateBuffer(&uniDesc);
 
    // 4. Create Readback Buffer
    wgpu::BufferDescriptor readDesc = {};
    readDesc.size = num_pixels * sizeof(float);
    readDesc.usage = wgpu::BufferUsage::MapRead | wgpu::BufferUsage::CopyDst;
    wgpu::Buffer readBuffer = GPU::getClassInstance().get_device().CreateBuffer(&readDesc);
 
    // 5. Compile Shader & Pipeline
    wgpu::ComputePipeline pipeline =
        GPU::getClassInstance().createPipeline("dist_shader", "updateDistShader");
 
    // 6. Bind Group
    wgpu::BindGroupEntry entries[3];
    entries[0].binding = 0;
    entries[0].textureView = inputTexture.CreateView();
    entries[1].binding = 1;
    entries[1].buffer = minDistBuffer;
    entries[1].size = distDesc.size;
    entries[2].binding = 2;
    entries[2].buffer = paramBuffer;
    entries[2].size = uniDesc.size;
 
    wgpu::BindGroupDescriptor bgDesc = {};
    bgDesc.layout = pipeline.GetBindGroupLayout(0);
    bgDesc.entryCount = 3;
    bgDesc.entries = entries;
    wgpu::BindGroup bindGroup = GPU::getClassInstance().get_device().CreateBindGroup(&bgDesc);
    // --- WEBGPU SETUP END ---
 
    // RNG Setup
    std::random_device rd;
    std::mt19937 gen(rd());
 
    // --- Step 1: Choose the first centroid randomly ---
    std::uniform_int_distribution<> dis(0, num_pixels - 1);
    int first_index = dis(gen);
    centroids.push_back(pixels[first_index]);
 
    // --- Step 2 & 3: Repeat until we have k centroids ---
    // static volatile bool done = false;
    bool* done = new bool(false);
 
    for (int i = 1; i < k; ++i) {
        *done = false;
        // A. Upload Current Centroid to GPU
        PixelT c = centroids.back();
        CentroidParams params;
        if constexpr (std::is_same_v<PixelT, ImageLib::LABAPixel<float>>) {
            params = CentroidParams {
                c.l / 255.0f, c.a / 255.0f, c.b / 255.0f, 1.0f, static_cast<uint32_t>(width)};
        } else {
            params = CentroidParams {
                c.red / 255.0f, c.green / 255.0f, c.blue / 255.0f, 1.0f,
                static_cast<uint32_t>(width)};
        }
 
        GPU::getClassInstance().get_queue().WriteBuffer(
            paramBuffer, 0, &params, sizeof(CentroidParams)
        );
 
        // B. Dispatch Shader (Updates min_dist buffer on GPU)
        wgpu::CommandEncoder encoder = GPU::getClassInstance().get_device().CreateCommandEncoder();
        wgpu::ComputePassEncoder pass = encoder.BeginComputePass();
        pass.SetPipeline(pipeline);
        pass.SetBindGroup(0, bindGroup);
        pass.DispatchWorkgroups((width + 15) / 16, (height + 15) / 16, 1);
        pass.End();
 
        // C. Copy Result to ReadBuffer
        encoder.CopyBufferToBuffer(minDistBuffer, 0, readBuffer, 0, readDesc.size);
        wgpu::CommandBuffer commands = encoder.Finish();
        GPU::getClassInstance().get_queue().Submit(1, &commands);
 
        // D. Map and Read
 
        readBuffer.MapAsync(
            wgpu::MapMode::Read, 0, readDesc.size, wgpu::CallbackMode::AllowProcessEvents,
            [](wgpu::MapAsyncStatus status, wgpu::StringView msg, void* userdata) {
                bool* flag = static_cast<bool*>(userdata);
                bool success = false;
                if (status == wgpu::MapAsyncStatus::Success) {
                    // std::cout << "Map success: " << msg.data << std::endl;
                    success = true;
                } else {
                    // Handle error
                    // std::cerr << "Map failed: " << msg.data << std::endl;
                    success = false;
                }
                *flag = true;
            },
            (void*)done
        );
 
        // E. Wait for GPU
        while (!*done) {
            GPU::getClassInstance().get_instance().ProcessEvents();
#if defined(__EMSCRIPTEN__)
            emscripten_sleep(10);
#endif
        }
 
        const float* dists = (const float*)readBuffer.GetConstMappedRange();
        // --- CPU SIDE: Selection Logic ---
        double sum_dist_sq = 0.0;
 
        // 1. Sum (We have to iterate anyway for roulette, so sum here)
        // Note: dists[] contains the SQUARED distance because shader calculated distSq
        for (size_t j = 0; j < num_pixels; ++j) {
            sum_dist_sq += dists[j];
        }
 
        // 2. Select
        std::uniform_real_distribution<> dist_selector(0.0, sum_dist_sq);
        double random_value = dist_selector(gen);
        double current_sum = 0.0;
        int selected_index = -1;
 
        for (size_t j = 0; j < num_pixels; ++j) {
            current_sum += dists[j];
            if (current_sum >= random_value) {
                selected_index = j;
                break;
            }
        }
 
        if (selected_index == -1)
            selected_index = num_pixels - 1;
 
        // Add new centroid
        centroids.push_back(pixels[selected_index]);
        readBuffer.Unmap();
#if defined(__EMSCRIPTEN__)
        emscripten_sleep(10);
#endif
    }
 
    std::copy(centroids.begin(), centroids.end(), out_centroids.begin());
 
    // explicit clean up
    if (inputTexture)
        inputTexture.Destroy();
    readBuffer.Destroy();
    minDistBuffer.Destroy();
    paramBuffer.Destroy();
    delete done;
 
#if defined(__EMSCRIPTEN__)
    emscripten_sleep(50);
#endif
}
 
void setup(
    ImageLib::Image<ImageLib::RGBAPixel<float>>& pixels,
    ImageLib::Image<ImageLib::LABAPixel<float>>& lab,
    ImageLib::Image<ImageLib::RGBAPixel<float>>& centroids,
    ImageLib::Image<ImageLib::LABAPixel<float>>& centroids_lab, const int32_t width,
    const int32_t height, const int32_t k, wgpu::Texture& inputTexture, wgpu::Texture& labelTexture,
    wgpu::Texture& centroidTexture, wgpu::TextureDescriptor& labelDesc,
    wgpu::TextureDescriptor& centroidDesc, wgpu::ComputePipeline& pipeline1,
    wgpu::ComputePipeline& pipeline2, wgpu::BindGroup& bindGroup1, wgpu::BindGroup& bindGroup2,
    const uint8_t color_space
) {
    int bytesPerPixel {16};
    const int32_t num_pixels {pixels.getSize()};
 
    wgpu::TextureDescriptor texDesc = {};
    texDesc.size = {static_cast<uint32_t>(width), static_cast<uint32_t>(height), 1};
    texDesc.format = wgpu::TextureFormat::RGBA32Float;
    texDesc.usage = wgpu::TextureUsage::TextureBinding | wgpu::TextureUsage::CopyDst;
    texDesc.label = "inputTexture";
    inputTexture = GPU::getClassInstance().get_device().CreateTexture(&texDesc);
 
    wgpu::TexelCopyTextureInfo dst = {};
    dst.texture = inputTexture;
    wgpu::TexelCopyBufferLayout layout = {};
    layout.offset = 0;
    layout.bytesPerRow = width * bytesPerPixel; // Tightly packed for upload
    layout.rowsPerImage = height;
 
    std::vector<float> pixels_;
    for (int i = 0; i < num_pixels; i++) {
        switch (color_space) {
        case COLOR_SPACE_OPTION_RGB: {
            auto p = pixels[i];
            pixels_.push_back(p.red / 255.0f);
            pixels_.push_back(p.green / 255.0f);
            pixels_.push_back(p.blue / 255.0f);
            pixels_.push_back(p.alpha / 255.0f);
            break;
        }
        case COLOR_SPACE_OPTION_CIELAB: {
            auto p = lab[i];
            pixels_.push_back(p.l / 255.0f);
            pixels_.push_back(p.a / 255.0f);
            pixels_.push_back(p.b / 255.0f);
            pixels_.push_back(p.alpha / 255.0f);
            break;
        }
        }
    }
 
    GPU::getClassInstance().get_queue().WriteTexture(
        &dst, pixels_.data(), pixels_.size() * sizeof(float), &layout, &texDesc.size
    );
 
    // centroids
    centroidDesc.size = {static_cast<uint32_t>(k), 1, 1};
    centroidDesc.format = wgpu::TextureFormat::RGBA32Float;
    centroidDesc.usage = wgpu::TextureUsage::TextureBinding | wgpu::TextureUsage::StorageBinding |
                         wgpu::TextureUsage::CopyDst | wgpu::TextureUsage::CopySrc;
    centroidDesc.label = "centroidTexture";
    centroidTexture = GPU::getClassInstance().get_device().CreateTexture(&centroidDesc);
 
    wgpu::TexelCopyTextureInfo cdst = {};
    cdst.texture = centroidTexture;
    wgpu::TexelCopyBufferLayout clayout = {};
    clayout.offset = 0;
    clayout.bytesPerRow = k * bytesPerPixel; // Tightly packed for upload
    clayout.rowsPerImage = 1;
 
    std::vector<float> centroids_; // rgba
    switch (color_space) {
    case COLOR_SPACE_OPTION_RGB: {
        for (int i = 0; i < k; i++) {
            auto p = centroids[i];
            centroids_.push_back(p.red / 255.0f);
            centroids_.push_back(p.green / 255.0f);
            centroids_.push_back(p.blue / 255.0f);
            centroids_.push_back(p.alpha / 255.0f);
        }
        break;
    }
    case COLOR_SPACE_OPTION_CIELAB: {
        for (int i = 0; i < k; i++) {
            auto p = centroids_lab[i];
            centroids_.push_back(p.l / 255.0f);
            centroids_.push_back(p.a / 255.0f);
            centroids_.push_back(p.b / 255.0f);
            centroids_.push_back(p.alpha / 255.0f);
        }
        break;
    }
    }
 
    GPU::getClassInstance().get_queue().WriteTexture(
        &cdst, centroids_.data(), centroids_.size() * sizeof(float), &clayout, &centroidDesc.size
    );
 
    // labels
    labelDesc.size = {static_cast<uint32_t>(width), static_cast<uint32_t>(height), 1};
    labelDesc.format = wgpu::TextureFormat::RGBA32Uint;
    labelDesc.usage = wgpu::TextureUsage::TextureBinding | wgpu::TextureUsage::StorageBinding |
                      wgpu::TextureUsage::CopyDst | wgpu::TextureUsage::CopySrc;
    labelDesc.label = "labelTexture";
    labelTexture = GPU::getClassInstance().get_device().CreateTexture(&labelDesc);
 
    // params
    Params params = {static_cast<uint32_t>(num_pixels), static_cast<uint32_t>(k)};
    wgpu::BufferDescriptor bufDesc = {};
    bufDesc.size = sizeof(Params);
    bufDesc.usage = wgpu::BufferUsage::Uniform | wgpu::BufferUsage::CopyDst;
    wgpu::Buffer paramBuffer = GPU::getClassInstance().get_device().CreateBuffer(&bufDesc);
    GPU::getClassInstance().get_queue().WriteBuffer(paramBuffer, 0, &params, sizeof(Params));
 
    // centroid accumulator
    std::vector<ClusterAccumulator> reset_centroids(k, {0, 0, 0, 0});
    wgpu::BufferDescriptor accDesc = {};
    accDesc.size = sizeof(ClusterAccumulator) * k;
    accDesc.usage = wgpu::BufferUsage::Storage | wgpu::BufferUsage::CopyDst;
    wgpu::Buffer accBuffer = GPU::getClassInstance().get_device().CreateBuffer(&accDesc);
    GPU::getClassInstance().get_queue().WriteBuffer(
        accBuffer, 0, reset_centroids.data(), accDesc.size
    );
 
    // shaders
    pipeline1 =
        GPU::getClassInstance().createPipeline("assign_update_shader", "assignUpdateShader");
    pipeline2 = GPU::getClassInstance().createPipeline("resolve_shader", "resolveShader");
 
    // binding groups
    wgpu::BindGroupDescriptor bindGroupDesc1 = {};
    bindGroupDesc1.layout = pipeline1.GetBindGroupLayout(0);
    wgpu::BindGroupEntry entries1[5]; // 4
    // Entry 0: Input Texture View
    entries1[0].binding = 0;
    entries1[0].textureView = inputTexture.CreateView();
    // Entry 1: Centroid Texture View
    entries1[1].binding = 1;
    entries1[1].textureView = centroidTexture.CreateView();
    // Entry 2: Label Texture View
    entries1[2].binding = 2;
    entries1[2].textureView = labelTexture.CreateView();
    // Entry 2: Uniform Buffer
    entries1[3].binding = 3;
    entries1[3].buffer = paramBuffer;
    entries1[3].size = sizeof(Params);
 
    entries1[4].binding = 4;
    entries1[4].buffer = accBuffer;
    entries1[4].size = sizeof(ClusterAccumulator) * k;
 
    bindGroupDesc1.entryCount = 5; // 4;
    bindGroupDesc1.entries = entries1;
    bindGroup1 = GPU::getClassInstance().get_device().CreateBindGroup(&bindGroupDesc1);
 
    wgpu::BindGroupDescriptor bindGroupDesc2 = {};
    bindGroupDesc2.layout = pipeline2.GetBindGroupLayout(0);
    wgpu::BindGroupEntry entries2[2];
    entries2[0].binding = 0;
    entries2[0].buffer = accBuffer;
    entries2[0].size = accDesc.size;
    entries2[1].binding = 1;
    entries2[1].textureView = centroidTexture.CreateView();
    bindGroupDesc2.entryCount = 2;
    bindGroupDesc2.entries = entries2;
    bindGroup2 = GPU::getClassInstance().get_device().CreateBindGroup(&bindGroupDesc2);
}
 
void kmeans_gpu(
    const uint8_t* data, uint8_t* out_data, int32_t* out_labels, const int32_t width,
    const int32_t height, const int32_t k, const int32_t max_iter, const uint8_t color_space
) {
    ImageLib::Image<ImageLib::RGBAPixel<float>> pixels;
    pixels.loadFromBuffer(data, width, height, ImageLib::RGBA_CONVERTER<float>);
    const int32_t num_pixels {pixels.getSize()};
 
    // width = k, height = 1
    // k centroids, initialized to rgba(0,0,0,255)
    // Init of each pixel is from default in Image constructor
    ImageLib::Image<ImageLib::RGBAPixel<float>> centroids {k, 1};
    ImageLib::Image<ImageLib::LABAPixel<float>> centroids_lab {k, 1};
    std::vector<int32_t> labels(num_pixels, -1);
 
    ImageLib::Image<ImageLib::LABAPixel<float>> lab(pixels.getWidth(), pixels.getHeight());
 
    if (color_space == COLOR_SPACE_OPTION_CIELAB) {
        for (int i {0}; i < pixels.getSize(); ++i) {
            rgb_to_lab<float, float>(pixels[i], lab[i]);
        }
    }
 
    std::cout << "starting" << std::endl;
    // Step 2: Initialize centroids
 
    switch (color_space) {
    case COLOR_SPACE_OPTION_RGB: {
        kMeansPlusPlusInitGpu<ImageLib::RGBAPixel<float>>(pixels, centroids, k, color_space);
        break;
    }
    case COLOR_SPACE_OPTION_CIELAB: {
        kMeansPlusPlusInitGpu<ImageLib::LABAPixel<float>>(lab, centroids_lab, k, color_space);
        break;
    }
    }
    std::cout << "kmeans++ init done" << std::endl;
    // Step 3: Run k-means iterations
 
    int bytesPerPixel {16}; // float pixels
 
    // shaders - 2 pipelines:
    // 1. assign and update clusters
    // 2. resolve cluster centroids
    wgpu::ComputePipeline pipeline1;
    wgpu::ComputePipeline pipeline2;
    wgpu::BindGroup bindGroup1;
    wgpu::BindGroup bindGroup2;
    wgpu::Texture inputTexture;
    wgpu::Texture labelTexture;
    wgpu::Texture centroidTexture;
    wgpu::TextureDescriptor labelDesc = {};
    wgpu::TextureDescriptor centroidDesc = {};
 
    // setup all textures and buffers needed for the kmeans loop on gpu
    setup(
        pixels, lab, centroids, centroids_lab, width, height, k, inputTexture, labelTexture,
        centroidTexture, labelDesc, centroidDesc, pipeline1, pipeline2, bindGroup1, bindGroup2,
        color_space
    );
 
    uint32_t wgX = (width + 15) / 16;
    uint32_t wgY = (height + 15) / 16;
 
    // Label Readback RGBA32Uint is 16 bytes/ pixel
    uint32_t bytesPerRowLabels =
        GPU::getAlignedBytesPerRow(width, static_cast<uint32_t>(bytesPerPixel));
    wgpu::BufferDescriptor readLabelsDesc = {};
    readLabelsDesc.size = bytesPerRowLabels * height;
    readLabelsDesc.usage = wgpu::BufferUsage::MapRead | wgpu::BufferUsage::CopyDst;
    wgpu::Buffer readLabelsBuffer =
        GPU::getClassInstance().get_device().CreateBuffer(&readLabelsDesc);
 
    // Centroid Readback
    uint32_t bytesPerRowCentroids =
        GPU::getAlignedBytesPerRow(width, static_cast<uint32_t>(bytesPerPixel));
    wgpu::BufferDescriptor readCentroidsDesc = {};
    readCentroidsDesc.size = bytesPerRowCentroids; // Height is 1
    readCentroidsDesc.usage = wgpu::BufferUsage::MapRead | wgpu::BufferUsage::CopyDst;
    wgpu::Buffer readCentroidsBuffer =
        GPU::getClassInstance().get_device().CreateBuffer(&readCentroidsDesc);
 
    // This is the actual KMeans loop
    std::cout << "start iterations" << std::endl;
    wgpu::CommandEncoder encoder = GPU::getClassInstance().get_device().CreateCommandEncoder();
    for (int32_t iter {0}; iter < max_iter; ++iter) {
        wgpu::ComputePassEncoder pass1 = encoder.BeginComputePass();
        pass1.SetPipeline(pipeline1);
        pass1.SetBindGroup(0, bindGroup1);
        pass1.DispatchWorkgroups(wgX, wgY);
        pass1.End();
 
        wgpu::ComputePassEncoder pass2 = encoder.BeginComputePass();
        pass2.SetPipeline(pipeline2);
        pass2.SetBindGroup(0, bindGroup2);
        pass2.DispatchWorkgroups((k + 255) / 256, 1);
        pass2.End();
    }
 
    // 3. Readback (After Loop Finishes)
 
    // Copy Labels
    wgpu::TexelCopyTextureInfo srcLabels = {};
    srcLabels.texture = labelTexture;
    wgpu::TexelCopyBufferInfo dstLabels = {};
    dstLabels.buffer = readLabelsBuffer;
    dstLabels.layout.bytesPerRow = bytesPerRowLabels;
    dstLabels.layout.rowsPerImage = height;
    encoder.CopyTextureToBuffer(&srcLabels, &dstLabels, &labelDesc.size);
 
    // Copy Centroids
    wgpu::TexelCopyTextureInfo srcCentroids = {};
    srcCentroids.texture = centroidTexture;
    wgpu::TexelCopyBufferInfo dstCentroids = {};
    dstCentroids.buffer = readCentroidsBuffer;
    dstCentroids.layout.bytesPerRow = bytesPerRowCentroids;
    dstCentroids.layout.rowsPerImage = 1;
    encoder.CopyTextureToBuffer(&srcCentroids, &dstCentroids, &centroidDesc.size);
 
    wgpu::CommandBuffer commands = encoder.Finish();
    GPU::getClassInstance().get_queue().Submit(1, &commands);
    std::cout << "done iterations" << std::endl;
 
    // 4. Map Async & Wait
    bool* done1 = new bool(false);
    bool* done2 = new bool(false);
 
    // Map Labels
    readLabelsBuffer.MapAsync(
        wgpu::MapMode::Read, 0, readLabelsDesc.size, wgpu::CallbackMode::AllowProcessEvents,
        [](wgpu::MapAsyncStatus status, wgpu::StringView msg, void* userdata) {
            bool* flag = static_cast<bool*>(userdata);
            bool success = false;
            if (status == wgpu::MapAsyncStatus::Success) {
                // std::cout << "Map success" << std::endl;
                success = true;
            }
            *flag = true;
        },
        (void*)done1
    );
 
    std::cout << "read out" << std::endl;
 
    while (!*done1) {
        GPU::getClassInstance().get_instance().ProcessEvents();
#if defined(__EMSCRIPTEN__)
        emscripten_sleep(10);
#endif
    }
 
    std::cout << "mapping labels" << std::endl;
    const uint8_t* mappedData = (const uint8_t*)readLabelsBuffer.GetConstMappedRange();
    // ... Copy data to your C++ vector ...
    // Copy row by row to remove padding and put data into 'result'
    for (size_t y = 0; y < height; ++y) {
        const uint8_t* rowPtr = mappedData + (y * bytesPerRowLabels);
        for (size_t x = 0; x < width; ++x) {
            const uint8_t* pixelPtr = rowPtr + (x * bytesPerPixel);
            uint32_t r = 0;
            std::memcpy(&r, pixelPtr, sizeof(uint32_t));
 
            size_t dstIndex = y * width + x;
            labels[dstIndex] = static_cast<int32_t>(r);
        }
    }
 
    readLabelsBuffer.Unmap();
 
    // Map Centroids
    readCentroidsBuffer.MapAsync(
        wgpu::MapMode::Read, 0, readCentroidsDesc.size, wgpu::CallbackMode::AllowProcessEvents,
        [](wgpu::MapAsyncStatus status, wgpu::StringView msg, void* userdata) {
            bool* flag = static_cast<bool*>(userdata);
            bool success = false;
            if (status == wgpu::MapAsyncStatus::Success) {
                // std::cout << "Map success" << std::endl;
                success = true;
            }
            *flag = true; // Signal completion
        },
        (void*)done2
    );
 
    while (!*done2) {
        GPU::getClassInstance().get_instance().ProcessEvents();
#if defined(__EMSCRIPTEN__)
        emscripten_sleep(10);
#endif
    }
 
    std::cout << "mapping centroids" << std::endl;
    const float* mappedDataFloat = (const float*)readCentroidsBuffer.GetConstMappedRange();
    // ... Copy data to your C++ vector ...
 
    for (int i = 0; i < k; i++) {
        // if CIELAB color space these represent l, a, b, alpha
        const float* centroidPtr = mappedDataFloat + (i * 4);
 
        float r = *(centroidPtr);
        float g = *(centroidPtr + 1);
        float b = *(centroidPtr + 2);
        float a = *(centroidPtr + 3);
        switch (color_space) {
        case COLOR_SPACE_OPTION_RGB: {
            centroids[i] = ImageLib::RGBAPixel<float>(r * 255.f, g * 255.f, b * 255.f, a * 255.f);
            break;
        }
        case COLOR_SPACE_OPTION_CIELAB: {
            centroids_lab[i] =
                ImageLib::LABAPixel<float>(r * 255.f, g * 255.f, b * 255.f, a * 255.f);
            break;
        }
        }
    }
 
    readCentroidsBuffer.Unmap();
 
    // Write the final centroid values to each pixel in the cluster
    if (color_space == COLOR_SPACE_OPTION_CIELAB) {
        for (int32_t i {0}; i < k; ++i) {
            lab_to_rgb<float, float>(centroids_lab[i], centroids[i]);
        }
    }
 
    for (int32_t i = 0; i < num_pixels; ++i) {
        const int32_t cluster = labels[i];
        out_data[i * 4 + 0] = static_cast<uint8_t>(centroids[cluster].red);
        out_data[i * 4 + 1] = static_cast<uint8_t>(centroids[cluster].green);
        out_data[i * 4 + 2] = static_cast<uint8_t>(centroids[cluster].blue);
        out_data[i * 4 + 3] = 255;
    }
 
    // Write labels to out_labels
    std::cout << "copying labels out" << std::endl;
    std::memcpy(out_labels, labels.data(), labels.size() * sizeof(int32_t));
 
    if (inputTexture)
        inputTexture.Destroy();
    if (labelTexture)
        labelTexture.Destroy();
    if (centroidTexture)
        centroidTexture.Destroy();
    readLabelsBuffer.Destroy();
    readCentroidsBuffer.Destroy();
    delete done1;
    delete done2;
 
    labels.clear();
    labels.shrink_to_fit();
#if defined(__EMSCRIPTEN__)
    emscripten_sleep(50);
#endif
}