Orthogonal regularization is wrong

[huangzhii]

According to the Arxiv paper https://arxiv.org/pdf/1609.07093.pdf, the orthogonal regularization should be: orth_loss = orth_loss + (reg * sym.abs().sum()) instead of: orth_loss = orth_loss + (reg * sym.sum()) since absolute opration was performed as per the paper. without abs, the loss will introduce negative value as well.

[kevinzakka]

Good catch, thanks @huangzhii !