Method constructor

tfjs-backend-webgl/src/lrn_packed_gpu.ts:27–111

(
      xShape: number[], radius: number, bias: number, alpha: number,
      beta: number)

  packedOutput = true;

  constructor(
      xShape: number[], radius: number, bias: number, alpha: number,
      beta: number) {
    const rad = radius;
    const maxD = xShape[3] - 1;
    this.outputShape = xShape;

    // optimize pow(bias + alpha * sum, -beta)
    // src: https://github.com/tensorflow/tensorflow/..
    // blob/26033a1644a9c4a5fbe3170ab2e864b6a4ccd4ca/..
    // tensorflow/core/kernels/mkl_lrn_op.cc#L320
    let powOperator;
    const basis = `float(${bias}) + float(${alpha}) * sum`;
    if (beta === 0.5) {
      powOperator = `inversesqrt(${basis})`;
    } else if (beta === 1.0) {
      powOperator = `1.0/(${basis})`;
    } else {
      powOperator = `exp(log(${basis}) * float(-${beta}));`;
    }

    this.userCode = `
      void main() {
        ivec4 coords = getOutputCoords();
        int b = coords.x;
        int r = coords.y;
        int c = coords.z;
        int d = coords.w;

        bool hasNextCol = d < ${this.outputShape[3]};
        bool hasNextRow = c < ${this.outputShape[2]};

        vec4 sum = vec4(0.);
        vec4 xFragAtOutputCoords = getX(b, r, c, d);

        vec4 xAtOutputCoords = vec4(
          getChannel(xFragAtOutputCoords, vec2(c, d)),
          hasNextCol ?
            getChannel(xFragAtOutputCoords, vec2(c, d + 1)) : 0.0,
          hasNextRow ?
            getChannel(xFragAtOutputCoords , vec2(c + 1, d)) : 0.0,
          (hasNextRow && hasNextCol) ?
            getChannel(xFragAtOutputCoords, vec2(c + 1, d + 1)) : 0.0
        );

        int firstChannel = d - ${rad};
        vec2 cache = vec2(0.);
        if(firstChannel >= 0){
          vec4 firstChannelFrag = getX(b, r, c, firstChannel);
          cache.x = getChannel(firstChannelFrag, vec2(c, firstChannel));
            if(hasNextRow){
              cache.y = getChannel(firstChannelFrag, vec2(c + 1, firstChannel));
            }
        }

        ivec2 depth = ivec2(d, d + 1);
        for (int j = - ${rad}; j <= ${rad}; j++) {
          ivec2 idx = depth + j;