mosesdecoder/lm/model.cc
2013-01-04 21:02:47 +00:00

309 lines
14 KiB
C++

#include "lm/model.hh"
#include "lm/blank.hh"
#include "lm/lm_exception.hh"
#include "lm/search_hashed.hh"
#include "lm/search_trie.hh"
#include "lm/read_arpa.hh"
#include "util/have.hh"
#include "util/murmur_hash.hh"
#include <algorithm>
#include <functional>
#include <numeric>
#include <cmath>
#include <limits>
namespace lm {
namespace ngram {
namespace detail {
template <class Search, class VocabularyT> const ModelType GenericModel<Search, VocabularyT>::kModelType = Search::kModelType;
template <class Search, class VocabularyT> uint64_t GenericModel<Search, VocabularyT>::Size(const std::vector<uint64_t> &counts, const Config &config) {
return VocabularyT::Size(counts[0], config) + Search::Size(counts, config);
}
template <class Search, class VocabularyT> void GenericModel<Search, VocabularyT>::SetupMemory(void *base, const std::vector<uint64_t> &counts, const Config &config) {
size_t goal_size = util::CheckOverflow(Size(counts, config));
uint8_t *start = static_cast<uint8_t*>(base);
size_t allocated = VocabularyT::Size(counts[0], config);
vocab_.SetupMemory(start, allocated, counts[0], config);
start += allocated;
start = search_.SetupMemory(start, counts, config);
if (static_cast<std::size_t>(start - static_cast<uint8_t*>(base)) != goal_size) UTIL_THROW(FormatLoadException, "The data structures took " << (start - static_cast<uint8_t*>(base)) << " but Size says they should take " << goal_size);
}
template <class Search, class VocabularyT> GenericModel<Search, VocabularyT>::GenericModel(const char *file, const Config &config) {
LoadLM(file, config, *this);
// g++ prints warnings unless these are fully initialized.
State begin_sentence = State();
begin_sentence.length = 1;
begin_sentence.words[0] = vocab_.BeginSentence();
typename Search::Node ignored_node;
bool ignored_independent_left;
uint64_t ignored_extend_left;
begin_sentence.backoff[0] = search_.LookupUnigram(begin_sentence.words[0], ignored_node, ignored_independent_left, ignored_extend_left).Backoff();
State null_context = State();
null_context.length = 0;
P::Init(begin_sentence, null_context, vocab_, search_.Order());
}
namespace {
void CheckCounts(const std::vector<uint64_t> &counts) {
UTIL_THROW_IF(counts.size() > KENLM_MAX_ORDER, FormatLoadException, "This model has order " << counts.size() << " but KenLM was compiled to support up to " << KENLM_MAX_ORDER << ". " << KENLM_ORDER_MESSAGE);
if (sizeof(uint64_t) > sizeof(std::size_t)) {
for (std::vector<uint64_t>::const_iterator i = counts.begin(); i != counts.end(); ++i) {
UTIL_THROW_IF(*i > static_cast<uint64_t>(std::numeric_limits<size_t>::max()), util::OverflowException, "This model has " << *i << " " << (i - counts.begin() + 1) << "-grams which is too many for 32-bit machines.");
}
}
}
} // namespace
template <class Search, class VocabularyT> void GenericModel<Search, VocabularyT>::InitializeFromBinary(void *start, const Parameters &params, const Config &config, int fd) {
CheckCounts(params.counts);
SetupMemory(start, params.counts, config);
vocab_.LoadedBinary(params.fixed.has_vocabulary, fd, config.enumerate_vocab);
search_.LoadedBinary();
}
template <class Search, class VocabularyT> void GenericModel<Search, VocabularyT>::InitializeFromARPA(const char *file, const Config &config) {
// Backing file is the ARPA. Steal it so we can make the backing file the mmap output if any.
util::FilePiece f(backing_.file.release(), file, config.ProgressMessages());
try {
std::vector<uint64_t> counts;
// File counts do not include pruned trigrams that extend to quadgrams etc. These will be fixed by search_.
ReadARPACounts(f, counts);
CheckCounts(counts);
if (counts.size() < 2) UTIL_THROW(FormatLoadException, "This ngram implementation assumes at least a bigram model.");
if (config.probing_multiplier <= 1.0) UTIL_THROW(ConfigException, "probing multiplier must be > 1.0");
std::size_t vocab_size = util::CheckOverflow(VocabularyT::Size(counts[0], config));
// Setup the binary file for writing the vocab lookup table. The search_ is responsible for growing the binary file to its needs.
vocab_.SetupMemory(SetupJustVocab(config, counts.size(), vocab_size, backing_), vocab_size, counts[0], config);
if (config.write_mmap) {
WriteWordsWrapper wrap(config.enumerate_vocab);
vocab_.ConfigureEnumerate(&wrap, counts[0]);
search_.InitializeFromARPA(file, f, counts, config, vocab_, backing_);
wrap.Write(backing_.file.get(), backing_.vocab.size() + vocab_.UnkCountChangePadding() + Search::Size(counts, config));
} else {
vocab_.ConfigureEnumerate(config.enumerate_vocab, counts[0]);
search_.InitializeFromARPA(file, f, counts, config, vocab_, backing_);
}
if (!vocab_.SawUnk()) {
assert(config.unknown_missing != THROW_UP);
// Default probabilities for unknown.
search_.UnknownUnigram().backoff = 0.0;
search_.UnknownUnigram().prob = config.unknown_missing_logprob;
}
FinishFile(config, kModelType, kVersion, counts, vocab_.UnkCountChangePadding(), backing_);
} catch (util::Exception &e) {
e << " Byte: " << f.Offset();
throw;
}
}
template <class Search, class VocabularyT> void GenericModel<Search, VocabularyT>::UpdateConfigFromBinary(int fd, const std::vector<uint64_t> &counts, Config &config) {
util::AdvanceOrThrow(fd, VocabularyT::Size(counts[0], config));
Search::UpdateConfigFromBinary(fd, counts, config);
}
template <class Search, class VocabularyT> FullScoreReturn GenericModel<Search, VocabularyT>::FullScore(const State &in_state, const WordIndex new_word, State &out_state) const {
FullScoreReturn ret = ScoreExceptBackoff(in_state.words, in_state.words + in_state.length, new_word, out_state);
for (const float *i = in_state.backoff + ret.ngram_length - 1; i < in_state.backoff + in_state.length; ++i) {
ret.prob += *i;
}
return ret;
}
template <class Search, class VocabularyT> FullScoreReturn GenericModel<Search, VocabularyT>::FullScoreForgotState(const WordIndex *context_rbegin, const WordIndex *context_rend, const WordIndex new_word, State &out_state) const {
context_rend = std::min(context_rend, context_rbegin + P::Order() - 1);
FullScoreReturn ret = ScoreExceptBackoff(context_rbegin, context_rend, new_word, out_state);
// Add the backoff weights for n-grams of order start to (context_rend - context_rbegin).
unsigned char start = ret.ngram_length;
if (context_rend - context_rbegin < static_cast<std::ptrdiff_t>(start)) return ret;
bool independent_left;
uint64_t extend_left;
typename Search::Node node;
if (start <= 1) {
ret.prob += search_.LookupUnigram(*context_rbegin, node, independent_left, extend_left).Backoff();
start = 2;
} else if (!search_.FastMakeNode(context_rbegin, context_rbegin + start - 1, node)) {
return ret;
}
// i is the order of the backoff we're looking for.
unsigned char order_minus_2 = start - 2;
for (const WordIndex *i = context_rbegin + start - 1; i < context_rend; ++i, ++order_minus_2) {
typename Search::MiddlePointer p(search_.LookupMiddle(order_minus_2, *i, node, independent_left, extend_left));
if (!p.Found()) break;
ret.prob += p.Backoff();
}
return ret;
}
template <class Search, class VocabularyT> void GenericModel<Search, VocabularyT>::GetState(const WordIndex *context_rbegin, const WordIndex *context_rend, State &out_state) const {
// Generate a state from context.
context_rend = std::min(context_rend, context_rbegin + P::Order() - 1);
if (context_rend == context_rbegin) {
out_state.length = 0;
return;
}
typename Search::Node node;
bool independent_left;
uint64_t extend_left;
out_state.backoff[0] = search_.LookupUnigram(*context_rbegin, node, independent_left, extend_left).Backoff();
out_state.length = HasExtension(out_state.backoff[0]) ? 1 : 0;
float *backoff_out = out_state.backoff + 1;
unsigned char order_minus_2 = 0;
for (const WordIndex *i = context_rbegin + 1; i < context_rend; ++i, ++backoff_out, ++order_minus_2) {
typename Search::MiddlePointer p(search_.LookupMiddle(order_minus_2, *i, node, independent_left, extend_left));
if (!p.Found()) {
std::copy(context_rbegin, context_rbegin + out_state.length, out_state.words);
return;
}
*backoff_out = p.Backoff();
if (HasExtension(*backoff_out)) out_state.length = i - context_rbegin + 1;
}
std::copy(context_rbegin, context_rbegin + out_state.length, out_state.words);
}
template <class Search, class VocabularyT> FullScoreReturn GenericModel<Search, VocabularyT>::ExtendLeft(
const WordIndex *add_rbegin, const WordIndex *add_rend,
const float *backoff_in,
uint64_t extend_pointer,
unsigned char extend_length,
float *backoff_out,
unsigned char &next_use) const {
FullScoreReturn ret;
typename Search::Node node;
if (extend_length == 1) {
typename Search::UnigramPointer ptr(search_.LookupUnigram(static_cast<WordIndex>(extend_pointer), node, ret.independent_left, ret.extend_left));
ret.rest = ptr.Rest();
ret.prob = ptr.Prob();
assert(!ret.independent_left);
} else {
typename Search::MiddlePointer ptr(search_.Unpack(extend_pointer, extend_length, node));
ret.rest = ptr.Rest();
ret.prob = ptr.Prob();
ret.extend_left = extend_pointer;
// If this function is called, then it does depend on left words.
ret.independent_left = false;
}
float subtract_me = ret.rest;
ret.ngram_length = extend_length;
next_use = extend_length;
ResumeScore(add_rbegin, add_rend, extend_length - 1, node, backoff_out, next_use, ret);
next_use -= extend_length;
// Charge backoffs.
for (const float *b = backoff_in + ret.ngram_length - extend_length; b < backoff_in + (add_rend - add_rbegin); ++b) ret.prob += *b;
ret.prob -= subtract_me;
ret.rest -= subtract_me;
return ret;
}
namespace {
// Do a paraonoid copy of history, assuming new_word has already been copied
// (hence the -1). out_state.length could be zero so I avoided using
// std::copy.
void CopyRemainingHistory(const WordIndex *from, State &out_state) {
WordIndex *out = out_state.words + 1;
const WordIndex *in_end = from + static_cast<ptrdiff_t>(out_state.length) - 1;
for (const WordIndex *in = from; in < in_end; ++in, ++out) *out = *in;
}
} // namespace
/* Ugly optimized function. Produce a score excluding backoff.
* The search goes in increasing order of ngram length.
* Context goes backward, so context_begin is the word immediately preceeding
* new_word.
*/
template <class Search, class VocabularyT> FullScoreReturn GenericModel<Search, VocabularyT>::ScoreExceptBackoff(
const WordIndex *const context_rbegin,
const WordIndex *const context_rend,
const WordIndex new_word,
State &out_state) const {
assert(new_word < vocab_.Bound());
FullScoreReturn ret;
// ret.ngram_length contains the last known non-blank ngram length.
ret.ngram_length = 1;
typename Search::Node node;
typename Search::UnigramPointer uni(search_.LookupUnigram(new_word, node, ret.independent_left, ret.extend_left));
out_state.backoff[0] = uni.Backoff();
ret.prob = uni.Prob();
ret.rest = uni.Rest();
// This is the length of the context that should be used for continuation to the right.
out_state.length = HasExtension(out_state.backoff[0]) ? 1 : 0;
// We'll write the word anyway since it will probably be used and does no harm being there.
out_state.words[0] = new_word;
if (context_rbegin == context_rend) return ret;
ResumeScore(context_rbegin, context_rend, 0, node, out_state.backoff + 1, out_state.length, ret);
CopyRemainingHistory(context_rbegin, out_state);
return ret;
}
template <class Search, class VocabularyT> void GenericModel<Search, VocabularyT>::ResumeScore(const WordIndex *hist_iter, const WordIndex *const context_rend, unsigned char order_minus_2, typename Search::Node &node, float *backoff_out, unsigned char &next_use, FullScoreReturn &ret) const {
for (; ; ++order_minus_2, ++hist_iter, ++backoff_out) {
if (hist_iter == context_rend) return;
if (ret.independent_left) return;
if (order_minus_2 == P::Order() - 2) break;
typename Search::MiddlePointer pointer(search_.LookupMiddle(order_minus_2, *hist_iter, node, ret.independent_left, ret.extend_left));
if (!pointer.Found()) return;
*backoff_out = pointer.Backoff();
ret.prob = pointer.Prob();
ret.rest = pointer.Rest();
ret.ngram_length = order_minus_2 + 2;
if (HasExtension(*backoff_out)) {
next_use = ret.ngram_length;
}
}
ret.independent_left = true;
typename Search::LongestPointer longest(search_.LookupLongest(*hist_iter, node));
if (longest.Found()) {
ret.prob = longest.Prob();
ret.rest = ret.prob;
// There is no blank in longest_.
ret.ngram_length = P::Order();
}
}
template <class Search, class VocabularyT> float GenericModel<Search, VocabularyT>::InternalUnRest(const uint64_t *pointers_begin, const uint64_t *pointers_end, unsigned char first_length) const {
float ret;
typename Search::Node node;
if (first_length == 1) {
if (pointers_begin >= pointers_end) return 0.0;
bool independent_left;
uint64_t extend_left;
typename Search::UnigramPointer ptr(search_.LookupUnigram(static_cast<WordIndex>(*pointers_begin), node, independent_left, extend_left));
ret = ptr.Prob() - ptr.Rest();
++first_length;
++pointers_begin;
} else {
ret = 0.0;
}
for (const uint64_t *i = pointers_begin; i < pointers_end; ++i, ++first_length) {
typename Search::MiddlePointer ptr(search_.Unpack(*i, first_length, node));
ret += ptr.Prob() - ptr.Rest();
}
return ret;
}
template class GenericModel<HashedSearch<BackoffValue>, ProbingVocabulary>;
template class GenericModel<HashedSearch<RestValue>, ProbingVocabulary>;
template class GenericModel<trie::TrieSearch<DontQuantize, trie::DontBhiksha>, SortedVocabulary>;
template class GenericModel<trie::TrieSearch<DontQuantize, trie::ArrayBhiksha>, SortedVocabulary>;
template class GenericModel<trie::TrieSearch<SeparatelyQuantize, trie::DontBhiksha>, SortedVocabulary>;
template class GenericModel<trie::TrieSearch<SeparatelyQuantize, trie::ArrayBhiksha>, SortedVocabulary>;
} // namespace detail
} // namespace ngram
} // namespace lm