Question about baum welch

[forsubhi]

I don't understand why do we use this method

float32
diag_norm(vector_t var,
      uint32 len)
{
    float32 log_det;
    float32 p;
    uint32 i;

    log_det = 0;

    for (i = 0; i < len; i++) {
    if (var[i] <= 0) {
        E_FATAL("Sanity check var[i] > 0 failed: %e\n", var[i]);
    }
    log_det += log(var[i]);
    }

    p = len * log(2.0 * M_PI);

    return - 0.5 * (log_det + p);
}

why isn't there any documentation about these methods ? !

[Nickolay V. Shmyrev]

You can learn Baum-Welch theory from the Rabiner's tutorial

A tutorial on hidden markov models and selected applications in speech
recognition (1989)
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.131.2084

[forsubhi]

thanks .. and is this part of a full book , and how can I get the full book ?