Method constructor

tfjs-backend-webgl/src/pad_packed_gpu.ts:30–86

(
      xShape: number[], paddings: Array<[number, number]>,
      constantValue: number)

  customUniforms = [{name: 'value', type: 'float' as UniformType}];

  constructor(
      xShape: number[], paddings: Array<[number, number]>,
      constantValue: number) {
    this.outputShape = paddings.map(
        (p, i) => p[0] /* beforePad */ + xShape[i] + p[1] /* afterPad */);
    const rank = xShape.length;
    const dtype = getCoordsDataType(rank);

    const start = paddings.map(p => p[0]).join(',');
    const end = paddings.map((p, i) => p[0] + xShape[i]).join(',');
    const coords = getChannels('rc', rank);
    const source = getChannels('source', rank);
    const cLimit = `${coords[rank - 1]} < ${this.outputShape[rank - 1]}`;
    const innerDims =
        rank === 1 ? 'source' : `vec2(${source.slice(-2).join()})`;

    const componentSetup = [
      `${dtype} rc = outputLoc;`, `${coords[rank - 1]} += 1;
       if(${cLimit}) {
      `,
      rank === 1 ? '' : `}
       rc = outputLoc;
       ${coords[rank - 2]} += 1;
       if(${coords[rank - 2]} < ${this.outputShape[rank - 2]}) {`,
      rank === 1 ? '' : `  ${coords[rank - 1]} += 1;
         if(${cLimit}) {`
    ];

    const paddingArea = rank === 1 ?
        'rc < start || rc >= end' :
        'any(lessThan(rc, start)) || any(greaterThanEqual(rc, end))';
    let mainLoop = '';
    for (let i = 0, j = rank === 1 ? 2 : 4; i < j; i++) {
      mainLoop += `
        ${componentSetup[i]}
        if (${paddingArea}) {
          result[${i}] = float(value);
        } else {
          ${dtype} source = rc - start;
          result[${i}] = getChannel(getX(${source.join()}), ${innerDims});
        }
      `;
    }
    mainLoop += (rank === 1 ? `} ` : `}}`);

    this.userCode = `
      const ${dtype} start = ${dtype}(${start});
      const ${dtype} end = ${dtype}(${end});

      void main() {
        ${dtype} outputLoc = getOutputCoords();
        vec4 result = vec4(0.);
        ${mainLoop}
        setOutput(result);
      }
    `;
  }
}