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import Shader from "./framework/WebGpu.js";
import { loadMNIST } from "./mnist_loader.js";
const batchSize = 1000;
const inputDimension = 28 * 28;
const hiddenDimension = 128;
const numberOfClasses = 10;
const learningRateValue = 0.05;
const numberOfEpochs = 20;
function drawMNISTPreview(canvas, pixelData, trueLabel, predictedLabel) {
const context = canvas.getContext("2d");
const image = context.createImageData(28, 28);
for (let i = 0; i < inputDimension; i++) {
const grayscale = pixelData[i] * 255;
const pixelIndex = i * 4;
image.data[pixelIndex + 0] = grayscale;
image.data[pixelIndex + 1] = grayscale;
image.data[pixelIndex + 2] = grayscale;
image.data[pixelIndex + 3] = 255;
}
context.putImageData(image, 0, 0);
canvas.nextLabel.textContent =
`GT: ${trueLabel} → Pred: ${predictedLabel}`;
}
async function main() {
if (!navigator.gpu) {
alert("WebGPU not supported");
return;
}
const adapter = await navigator.gpu.requestAdapter();
const device = await adapter.requestDevice();
// Load MNIST subset → inputImages & targetLabels are GPU buffers
const mnist = await loadMNIST(device, batchSize);
const inputImages = mnist.images;
const targetLabels = mnist.labels;
const layer1Sizes = new Uint32Array([inputDimension, hiddenDimension, batchSize]);
const layer2Sizes = new Uint32Array([hiddenDimension, numberOfClasses, batchSize]);
//
// === Create Shader Instances ===
//
const forwardDenseLayer1 = new Shader(device);
await forwardDenseLayer1.setup("./shaders/neural/forward_dense_layer1.wgsl");
const forwardDenseLayer2 = new Shader(device);
await forwardDenseLayer2.setup("./shaders/neural/forward_dense_layer2.wgsl");
const softmaxCrossEntropyBackward = new Shader(device);
await softmaxCrossEntropyBackward.setup("./shaders/neural/softmax_cross_entropy_backward.wgsl");
const gradientsDenseLayer2 = new Shader(device);
await gradientsDenseLayer2.setup("./shaders/neural/gradients_dense_layer2.wgsl");
const gradientsDenseLayer1 = new Shader(device);
await gradientsDenseLayer1.setup("./shaders/neural/gradients_dense_layer1.wgsl");
const sgdOptimizerUpdate = new Shader(device);
await sgdOptimizerUpdate.setup("./shaders/neural/sgd_optimizer_update.wgsl");
//
// === Model Parameters ===
//
const weightLayer1 = new Float32Array(inputDimension * hiddenDimension)
.map(() => (Math.random() * Math.sqrt(2.0 / inputDimension)) - (Math.sqrt(2.0 / inputDimension) / 2));
const biasLayer1 = new Float32Array(hiddenDimension);
const weightLayer2 = new Float32Array(hiddenDimension * numberOfClasses)
.map(() => (Math.random() * Math.sqrt(2.0 / hiddenDimension)) - (Math.sqrt(2.0 / hiddenDimension) / 2));
const biasLayer2 = new Float32Array(numberOfClasses);
//
// === Bind Buffers to Shaders ===
//
forwardDenseLayer1.setVariable("inputImages", inputImages);
forwardDenseLayer1.setVariable("weightLayer1", weightLayer1);
forwardDenseLayer1.setVariable("biasLayer1", biasLayer1);
forwardDenseLayer1.setVariable("layer1Sizes", layer1Sizes, "uniform");
forwardDenseLayer2.setBuffer("hiddenActivations", forwardDenseLayer1.getBuffer("hiddenActivations"));
forwardDenseLayer2.setVariable("weightLayer2", weightLayer2);
forwardDenseLayer2.setVariable("biasLayer2", biasLayer2);
forwardDenseLayer2.setVariable("layer2Sizes", layer2Sizes, "uniform");
softmaxCrossEntropyBackward.setBuffer("outputLogits", forwardDenseLayer2.getBuffer("outputLogits"));
softmaxCrossEntropyBackward.setVariable("targetLabels", targetLabels);
softmaxCrossEntropyBackward.setVariable("layer2Sizes", layer2Sizes, "uniform");
gradientsDenseLayer2.setBuffer("hiddenActivations", forwardDenseLayer1.getBuffer("hiddenActivations"));
gradientsDenseLayer2.setBuffer("gradientLogits", softmaxCrossEntropyBackward.getBuffer("gradientLogits"));
//gradientsDenseLayer2.setBuffer("gradientWeightLayer2", null);
gradientsDenseLayer2.setBuffer("weightLayer2", forwardDenseLayer2.getBuffer("weightLayer2"));
//gradientsDenseLayer2.setBuffer("gradientBiasLayer2", null);
//gradientsDenseLayer2.setBuffer("gradientHidden", null);
gradientsDenseLayer2.setVariable("layer2Sizes", layer2Sizes, "uniform");
gradientsDenseLayer1.setVariable("inputImages", inputImages);
gradientsDenseLayer1.setBuffer("gradientHidden", gradientsDenseLayer2.getBuffer("gradientHidden"));
//gradientsDenseLayer1.setBuffer("gradientWeightLayer1", null);
//gradientsDenseLayer1.setBuffer("gradientBiasLayer1", null);
gradientsDenseLayer1.setVariable("layer1Sizes", layer1Sizes, "uniform");
sgdOptimizerUpdate.setBuffer("weightLayer1", forwardDenseLayer1.getBuffer("weightLayer1"));
sgdOptimizerUpdate.setBuffer("biasLayer1", forwardDenseLayer1.getBuffer("biasLayer1"));
sgdOptimizerUpdate.setBuffer("gradientWeightLayer1", gradientsDenseLayer1.getBuffer("gradientWeightLayer1"));
sgdOptimizerUpdate.setBuffer("gradientBiasLayer1", gradientsDenseLayer1.getBuffer("gradientBiasLayer1"));
sgdOptimizerUpdate.setBuffer("weightLayer2", forwardDenseLayer2.getBuffer("weightLayer2"));
sgdOptimizerUpdate.setBuffer("biasLayer2", forwardDenseLayer2.getBuffer("biasLayer2"));
sgdOptimizerUpdate.setBuffer("gradientWeightLayer2", gradientsDenseLayer2.getBuffer("gradientWeightLayer2"));
sgdOptimizerUpdate.setBuffer("gradientBiasLayer2", gradientsDenseLayer2.getBuffer("gradientBiasLayer2"));
sgdOptimizerUpdate.setVariable("learningRate", new Float32Array([learningRateValue]), "uniform");
//
// === UI ===
//
const logOutput = document.getElementById("log");
const previewContainer = document.getElementById("preview");
const numberOfPreviewImages = 6;
const previewIndices = Array.from({ length: numberOfPreviewImages },
() => Math.floor(Math.random() * batchSize));
const previewCanvases = previewIndices.map(() => {
const container = document.createElement("div");
container.className = "previewItem";
const canvas = document.createElement("canvas");
canvas.width = canvas.height = 28;
const label = document.createElement("div");
canvas.nextLabel = label;
container.appendChild(canvas);
container.appendChild(label);
previewContainer.appendChild(container);
return canvas;
});
//
// === Training ===
//
document.getElementById("trainBtn").onclick = async () => {
for (let epoch = 0; epoch < numberOfEpochs; epoch++) {
await forwardDenseLayer1.execute(batchSize);
await forwardDenseLayer2.execute(batchSize);
await softmaxCrossEntropyBackward.execute(batchSize);
const wgSize = 64;
// Grad Layer 2
await gradientsDenseLayer2.execute(
Math.ceil((batchSize * numberOfClasses + hiddenDimension * numberOfClasses) / wgSize)
);
// Grad Layer 1
await gradientsDenseLayer1.execute(
Math.ceil((batchSize * hiddenDimension + inputDimension * hiddenDimension) / wgSize)
);
// SGD
await sgdOptimizerUpdate.execute(
Math.ceil((weightLayer1.length + biasLayer1.length +
weightLayer2.length + biasLayer2.length) / wgSize)
);
// Loss
const lossValues = await softmaxCrossEntropyBackward.debugBuffer("crossEntropyLoss");
const averageLoss = lossValues.reduce((a,b)=>a+b,0) / batchSize;
logOutput.textContent += `Epoch ${epoch}: Loss = ${averageLoss.toFixed(4)}\n`;
// Accuracy
const logits = await forwardDenseLayer2.debugBuffer("outputLogits");
let correctCount = 0;
for (let i = 0; i < batchSize; i++) {
let bestValue = -1e9;
let bestClass = 0;
for (let c = 0; c < numberOfClasses; c++) {
const value = logits[i*numberOfClasses+c];
if (value > bestValue) { bestValue = value; bestClass = c; }
}
if (bestClass === targetLabels[i]) correctCount++;
}
const accuracy = correctCount / batchSize;
logOutput.textContent += `Accuracy: ${(accuracy*100).toFixed(2)}%\n`;
// Update preview images
for (let k = 0; k < numberOfPreviewImages; k++) {
const index = previewIndices[k];
const image = inputImages.subarray(
index*inputDimension, (index+1)*inputDimension
);
let bestValue = -1e9;
let bestClass = 0;
for (let c = 0; c < numberOfClasses; c++) {
const value = logits[index*numberOfClasses+c];
if (value > bestValue) { bestValue = value; bestClass = c; }
}
drawMNISTPreview(
previewCanvases[k],
image,
targetLabels[index],
bestClass
);
}
}
};
}
main();