the F norm ||Wi|| == 1 avoiding trivial solution

In Optimization part of our paper (Section 3.1), we mentioned:

We also add a constrain to this formulation, which avoids trivial solution.

Given any solution, we can get better solution by fixing and making .

Thus the L1 regularization term in Equ (2) becomes invalid. Then both optimization problems (2) and (4) satisfy, but no sparse solution is obtained.