web-rwkv 0.10.20

An implementation of the RWKV language model in pure WebGPU.
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struct View {
    shape: vec4<u32>,
    stride: vec4<u32>,
    offset: vec4<u32>,
};

@group(0) @binding(0) var<uniform> source: View;
@group(0) @binding(1) var<uniform> destination: View;

#ifdef IN_FP16
@group(0) @binding(2) var<storage, read> input: array<vec2<u32>>;      // (B?, T?, C)
#else
@group(0) @binding(2) var<storage, read> input: array<vec4<f32>>;      // (B?, T?, C)
#endif
#ifdef OUT_FP16
@group(0) @binding(3) var<storage, read_write> output: array<vec2<u32>>;    // (B, T, C)
#else
@group(0) @binding(3) var<storage, read_write> output: array<vec4<f32>>;    // (B, T, C)
#endif

// ACTIVATION_DEFINE

fn pack4x16float(x: vec4<f32>) -> vec2<u32> {
    return vec2<u32>(pack2x16float(x.xy), pack2x16float(x.zw));
}

fn unpack4x16float(x: vec2<u32>) -> vec4<f32> {
    return vec4<f32>(unpack2x16float(x.x), unpack2x16float(x.y));
}

fn compute_index(view: View, batch: u32, token: u32, index: u32) -> u32 {
    let stride = view.stride.x >> 2u;
    let offset = vec3<u32>(view.offset.zy, view.offset.x >> 2u);
    return dot(vec3<u32>(batch, token, index) + offset, vec3<u32>(view.stride.y * stride, stride, 1u));
}

@compute @workgroup_size(BLOCK_SIZE, 1, 1)
fn add(@builtin(global_invocation_id) invocation_id: vec3<u32>) {
    let stride = destination.shape.x / 4u;
    let index = invocation_id.x;
    let token = invocation_id.y;
    let batch = invocation_id.z;

    if index < stride {
#ifdef IN_FP16
        let x = unpack4x16float(input[compute_index(source, select(batch, 0u, source.shape.z == 1u), select(token, 0u, source.shape.y == 1u), index)]);
#else
        let x = input[compute_index(source, select(batch, 0u, source.shape.z == 1u), select(token, 0u, source.shape.y == 1u), index)];
#endif
        let bti = compute_index(destination, batch, token, index);
#ifdef OUT_FP16
        output[bti] = pack4x16float(ACT_OUT(ACT_X(x) + ACT_Y(unpack4x16float(output[bti]))));
#else
        output[bti] = ACT_OUT(ACT_X(x) + ACT_Y(output[bti]));
#endif
    }
}

@compute @workgroup_size(BLOCK_SIZE, 1, 1)
fn mul(@builtin(global_invocation_id) invocation_id: vec3<u32>) {
    let stride = destination.shape.x / 4u;
    let index = invocation_id.x;
    let token = invocation_id.y;
    let batch = invocation_id.z;

    if index < stride {
#ifdef IN_FP16
        let x = unpack4x16float(input[compute_index(source, select(batch, 0u, source.shape.z == 1u), select(token, 0u, source.shape.y == 1u), index)]);
#else
        let x = input[compute_index(source, select(batch, 0u, source.shape.z == 1u), select(token, 0u, source.shape.y == 1u), index)];
#endif
        let bti = compute_index(destination, batch, token, index);
#ifdef OUT_FP16
        output[bti] = pack4x16float(ACT_OUT(ACT_X(x) * ACT_Y(unpack4x16float(output[bti]))));
#else
        output[bti] = ACT_OUT(ACT_X(x) * ACT_Y(output[bti]));
#endif
    }
}