ValuedAction DESPOT::Evaluate(VNode* root, vector<State*>& particles,
RandomStreams& streams, POMCPPrior* prior, const DSPOMDP* model) {
double value = 0;
for (int i = 0; i < particles.size(); i++) {
particles[i]->scenario_id = i;
}
for (int i = 0; i < particles.size(); i++) {
State* particle = particles[i];
VNode* cur = root;
State* copy = model->Copy(particle);
double discount = 1.0;
double val = 0;
int steps = 0;
while (!streams.Exhausted()) {
int action =
(cur != NULL) ?
OptimalAction(cur).action : prior->GetAction(*copy);
assert(action != -1);
double reward;
OBS_TYPE obs;
bool terminal = model->Step(*copy, streams.Entry(copy->scenario_id),
action, reward, obs);
val += discount * reward;
discount *= Discount();
if (!terminal) {
prior->Add(action, obs);
streams.Advance();
steps++;
if (cur != NULL && !cur->IsLeaf()) {
QNode* qnode = cur->Child(action);
map<OBS_TYPE, VNode*>& vnodes = qnode->children();
cur = vnodes.find(obs) != vnodes.end() ? vnodes[obs] : NULL;
}
} else {
break;
}
}
for (int i = 0; i < steps; i++) {
streams.Back();
prior->PopLast();
}
model->Free(copy);
value += val;
}
return ValuedAction(OptimalAction(root).action, value / particles.size());
}
VNode* DESPOT::Trial(VNode* root, RandomStreams& streams,
ScenarioLowerBound* lower_bound, ScenarioUpperBound* upper_bound,
const DSPOMDP* model, History& history, SearchStatistics* statistics) {
VNode* cur = root;
int hist_size = history.Size();
do {
if (statistics != NULL
&& cur->depth() > statistics->longest_trial_length) {
statistics->longest_trial_length = cur->depth();
}
ExploitBlockers(cur);
if (Gap(cur) == 0) {
break;
}
if (cur->IsLeaf()) {
double start = clock();
Expand(cur, lower_bound, upper_bound, model, streams, history);
if (statistics != NULL) {
statistics->time_node_expansion += (double) (clock() - start)
/ CLOCKS_PER_SEC;
statistics->num_expanded_nodes++;
statistics->num_tree_particles += cur->particles().size();
}
}
double start = clock();
QNode* qstar = SelectBestUpperBoundNode(cur);
VNode* next = SelectBestWEUNode(qstar);
if (statistics != NULL) {
statistics->time_path += (clock() - start) / CLOCKS_PER_SEC;
}
if (next == NULL) {
break;
}
cur = next;
history.Add(qstar->edge(), cur->edge());
} while (cur->depth() < Globals::config.search_depth && WEU(cur) > 0);
history.Truncate(hist_size);
return cur;
}