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#include "rule_factory.h"
#include <cassert>
#include <memory>
#include <queue>
#include <vector>
#include "matching_comparator.h"
#include "phrase.h"
#include "suffix_array.h"
#include "vocabulary.h"
using namespace std;
using namespace tr1;
struct State {
State(int start, int end, const vector<int>& phrase,
const vector<int>& subpatterns_start, shared_ptr<TrieNode> node,
bool starts_with_x) :
start(start), end(end), phrase(phrase),
subpatterns_start(subpatterns_start), node(node),
starts_with_x(starts_with_x) {}
int start, end;
vector<int> phrase, subpatterns_start;
shared_ptr<TrieNode> node;
bool starts_with_x;
};
HieroCachingRuleFactory::HieroCachingRuleFactory(
shared_ptr<SuffixArray> source_suffix_array,
shared_ptr<DataArray> target_data_array,
const Alignment& alignment,
const shared_ptr<Vocabulary>& vocabulary,
const Precomputation& precomputation,
int min_gap_size,
int max_rule_span,
int max_nonterminals,
int max_rule_symbols,
bool use_baeza_yates) :
matchings_finder(source_suffix_array),
intersector(vocabulary, precomputation, source_suffix_array,
make_shared<MatchingComparator>(min_gap_size, max_rule_span),
use_baeza_yates),
phrase_builder(vocabulary),
rule_extractor(source_suffix_array, target_data_array, alignment),
vocabulary(vocabulary),
min_gap_size(min_gap_size),
max_rule_span(max_rule_span),
max_nonterminals(max_nonterminals),
max_chunks(max_nonterminals + 1),
max_rule_symbols(max_rule_symbols) {}
void HieroCachingRuleFactory::GetGrammar(const vector<int>& word_ids) {
// Clear cache for every new sentence.
trie.Reset();
shared_ptr<TrieNode> root = trie.GetRoot();
int first_x = vocabulary->GetNonterminalIndex(1);
shared_ptr<TrieNode> x_root(new TrieNode(root));
root->AddChild(first_x, x_root);
queue<State> states;
for (size_t i = 0; i < word_ids.size(); ++i) {
states.push(State(i, i, vector<int>(), vector<int>(1, i), root, false));
}
for (size_t i = min_gap_size; i < word_ids.size(); ++i) {
states.push(State(i - min_gap_size, i, vector<int>(1, first_x),
vector<int>(1, i), x_root, true));
}
while (!states.empty()) {
State state = states.front();
states.pop();
shared_ptr<TrieNode> node = state.node;
vector<int> phrase = state.phrase;
int word_id = word_ids[state.end];
phrase.push_back(word_id);
Phrase next_phrase = phrase_builder.Build(phrase);
shared_ptr<TrieNode> next_node;
if (CannotHaveMatchings(node, word_id)) {
if (!node->HasChild(word_id)) {
node->AddChild(word_id, shared_ptr<TrieNode>());
}
continue;
}
if (RequiresLookup(node, word_id)) {
shared_ptr<TrieNode> next_suffix_link =
node->suffix_link->GetChild(word_id);
if (state.starts_with_x) {
// If the phrase starts with a non terminal, we simply use the matchings
// from the suffix link.
next_node = shared_ptr<TrieNode>(new TrieNode(
next_suffix_link, next_phrase, next_suffix_link->matchings));
} else {
PhraseLocation phrase_location;
if (next_phrase.Arity() > 0) {
phrase_location = intersector.Intersect(
node->phrase,
node->matchings,
next_suffix_link->phrase,
next_suffix_link->matchings,
next_phrase);
} else {
phrase_location = matchings_finder.Find(
node->matchings,
vocabulary->GetTerminalValue(word_id),
state.phrase.size());
}
if (phrase_location.IsEmpty()) {
continue;
}
next_node = shared_ptr<TrieNode>(new TrieNode(
next_suffix_link, next_phrase, phrase_location));
}
node->AddChild(word_id, next_node);
// Automatically adds a trailing non terminal if allowed. Simply copy the
// matchings from the prefix node.
AddTrailingNonterminal(phrase, next_phrase, next_node,
state.starts_with_x);
if (!state.starts_with_x) {
rule_extractor.ExtractRules();
}
} else {
next_node = node->GetChild(word_id);
}
vector<State> new_states = ExtendState(word_ids, state, phrase, next_phrase,
next_node);
for (State new_state: new_states) {
states.push(new_state);
}
}
}
bool HieroCachingRuleFactory::CannotHaveMatchings(
shared_ptr<TrieNode> node, int word_id) {
if (node->HasChild(word_id) && node->GetChild(word_id) == NULL) {
return true;
}
shared_ptr<TrieNode> suffix_link = node->suffix_link;
return suffix_link != NULL && suffix_link->GetChild(word_id) == NULL;
}
bool HieroCachingRuleFactory::RequiresLookup(
shared_ptr<TrieNode> node, int word_id) {
return !node->HasChild(word_id);
}
void HieroCachingRuleFactory::AddTrailingNonterminal(
vector<int> symbols,
const Phrase& prefix,
const shared_ptr<TrieNode>& prefix_node,
bool starts_with_x) {
if (prefix.Arity() >= max_nonterminals) {
return;
}
int var_id = vocabulary->GetNonterminalIndex(prefix.Arity() + 1);
symbols.push_back(var_id);
Phrase var_phrase = phrase_builder.Build(symbols);
int suffix_var_id = vocabulary->GetNonterminalIndex(
prefix.Arity() + starts_with_x == 0);
shared_ptr<TrieNode> var_suffix_link =
prefix_node->suffix_link->GetChild(suffix_var_id);
prefix_node->AddChild(var_id, shared_ptr<TrieNode>(new TrieNode(
var_suffix_link, var_phrase, prefix_node->matchings)));
}
vector<State> HieroCachingRuleFactory::ExtendState(
const vector<int>& word_ids,
const State& state,
vector<int> symbols,
const Phrase& phrase,
const shared_ptr<TrieNode>& node) {
int span = state.end - state.start;
vector<State> new_states;
if (symbols.size() >= max_rule_symbols || state.end + 1 >= word_ids.size() ||
span >= max_rule_span) {
return new_states;
}
new_states.push_back(State(state.start, state.end + 1, symbols,
state.subpatterns_start, node, state.starts_with_x));
int num_subpatterns = phrase.Arity() + state.starts_with_x == 0;
if (symbols.size() + 1 >= max_rule_symbols ||
phrase.Arity() >= max_nonterminals ||
num_subpatterns >= max_chunks) {
return new_states;
}
int var_id = vocabulary->GetNonterminalIndex(phrase.Arity() + 1);
symbols.push_back(var_id);
vector<int> subpatterns_start = state.subpatterns_start;
size_t i = state.end + 1 + min_gap_size;
while (i < word_ids.size() && i - state.start <= max_rule_span) {
subpatterns_start.push_back(i);
new_states.push_back(State(state.start, i, symbols, subpatterns_start,
node->GetChild(var_id), state.starts_with_x));
subpatterns_start.pop_back();
++i;
}
return new_states;
}
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