public INDArray mmul(INDArray x, INDArray y) {
    NDValidation.validateNumerical("mmul", "x", x);
    NDValidation.validateNumerical("mmul", "y", y);
    return Nd4j.exec(new org.nd4j.linalg.api.ops.impl.reduce.Mmul(x, y, false, false, false))[0];
  }