confusion in function c_ctr::stochastic_learn_map_estimate

[LanternYing]

when I look at the function c_ctr::stochastic_learn_map_estimate,I have three questions:

1. when updating the u and v, why the regulation changes from lambda_u and lambda_v to lambda_u/2n and lambda_v / (2 * items->m_vec_len[j]), which seems that it doesn't match the update equation according to stochastic Newton-Raphson rules.
2. I can't understand parameter 'lda_regression'. What does it mean?
3. In the loss function, we have $c_{ij}$. However, in the function, I cannot see the para->a and para->b in neither update rules nor the likelihood computation.
   @altosaar can you help me? Thanks.