int MHSampler::doc_proposal(SLDADoc& doc, Sentence& sent) {
int old_topic = sent.topic;
int new_topic = -1;
double dart = rand() * (doc.size() + _model->alpha_sum());
if (dart < doc.size()) {
int token_index = static_cast<int>(dart);
new_topic = doc.sent(token_index).topic;
} else {
// 命中文档先验部分, 则随机进行主题采样
new_topic = rand_k(_model->num_topics());
}
if (new_topic != old_topic) {
float proportion_old = proportional_funtion(doc, sent, old_topic);
float proportion_new = proportional_funtion(doc, sent, new_topic);
float proposal_old = doc_proposal_distribution(doc, old_topic);
float proposal_new = doc_proposal_distribution(doc, new_topic);
double transition_prob = (proportion_new * proposal_old) / (proportion_old * proposal_new);
double rejection = rand();
int mask = -(rejection < transition_prob);
return (new_topic & mask) | (old_topic & ~mask);
}
return new_topic;
}
void test_init(uint32_t* seed)
{
// Randomize variable locations
uint32_t rs[NUM_VARS];
for (int i = 0; i < NUM_VARS; i++) {
retry:
rs[i] = rand_k(seed, NUM_LOCS - 1);
for (int j = 0; j < i; j++)
if (rs[i] == rs[j]) goto retry;
}
// Intialise variables
test.locs = (var_t*) LOCS_BASE;
for (int i = 0; i < NUM_VARS; i++) {
test.vars[i] = &test.locs[rs[i]*LOC_GRAIN];
*test.vars[i] = 0;
}
// Set random start delays
uint32_t max = 0;
for (int i = 0; i < NUM_PROCESSES; i++)
if (test.start_times[i] > max) max = test.start_times[i];
for (int i = 0; i < NUM_PROCESSES; i++)
test.delays[i] = rand_k(seed, test.start_times[i] < max ? 6 : 2);
}
