public SDVariable sub(String name, SDVariable x, SDVariable y) {
    SDValidation.validateNumerical("sub", "x", x);
    SDValidation.validateNumerical("sub", "y", y);
    SDVariable out =  new org.nd4j.linalg.api.ops.impl.transforms.pairwise.arithmetic.SubOp(sd,x, y).outputVariable();
    return sd.updateVariableNameAndReference(out, name);