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mosesdecoder/lm/search_trie.cc

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/* This is where the trie is built. It's on-disk. */
#include "lm/search_trie.hh"
#include "lm/bhiksha.hh"
#include "lm/binary_format.hh"
#include "lm/blank.hh"
#include "lm/lm_exception.hh"
#include "lm/max_order.hh"
#include "lm/quantize.hh"
#include "lm/trie.hh"
#include "lm/trie_sort.hh"
#include "lm/vocab.hh"
#include "lm/weights.hh"
#include "lm/word_index.hh"
#include "util/ersatz_progress.hh"
#include "util/mmap.hh"
#include "util/proxy_iterator.hh"
#include "util/scoped.hh"
#include "util/sized_iterator.hh"
#include <algorithm>
#include <cstring>
#include <cstdio>
#include <cstdlib>
#include <queue>
#include <limits>
#include <numeric>
#include <vector>
#if defined(_WIN32) || defined(_WIN64)
#include <windows.h>
#endif
namespace lm {
namespace ngram {
namespace trie {
namespace {
void ReadOrThrow(FILE *from, void *data, size_t size) {
UTIL_THROW_IF(1 != std::fread(data, size, 1, from), util::ErrnoException, "Short read");
}
int Compare(unsigned char order, const void *first_void, const void *second_void) {
const WordIndex *first = reinterpret_cast<const WordIndex*>(first_void), *second = reinterpret_cast<const WordIndex*>(second_void);
const WordIndex *end = first + order;
for (; first != end; ++first, ++second) {
if (*first < *second) return -1;
if (*first > *second) return 1;
}
return 0;
}
struct ProbPointer {
unsigned char array;
uint64_t index;
};
// Array of n-grams and float indices.
class BackoffMessages {
public:
void Init(std::size_t entry_size) {
current_ = NULL;
allocated_ = NULL;
entry_size_ = entry_size;
}
void Add(const WordIndex *to, ProbPointer index) {
while (current_ + entry_size_ > allocated_) {
std::size_t allocated_size = allocated_ - (uint8_t*)backing_.get();
Resize(std::max<std::size_t>(allocated_size * 2, entry_size_));
}
memcpy(current_, to, entry_size_ - sizeof(ProbPointer));
*reinterpret_cast<ProbPointer*>(current_ + entry_size_ - sizeof(ProbPointer)) = index;
current_ += entry_size_;
}
void Apply(float *const *const base, FILE *unigrams) {
FinishedAdding();
if (current_ == allocated_) return;
rewind(unigrams);
ProbBackoff weights;
WordIndex unigram = 0;
ReadOrThrow(unigrams, &weights, sizeof(weights));
for (; current_ != allocated_; current_ += entry_size_) {
const WordIndex &cur_word = *reinterpret_cast<const WordIndex*>(current_);
for (; unigram < cur_word; ++unigram) {
ReadOrThrow(unigrams, &weights, sizeof(weights));
}
if (!HasExtension(weights.backoff)) {
weights.backoff = kExtensionBackoff;
UTIL_THROW_IF(fseek(unigrams, -sizeof(weights), SEEK_CUR), util::ErrnoException, "Seeking backwards to denote unigram extension failed.");
util::WriteOrThrow(unigrams, &weights, sizeof(weights));
}
const ProbPointer &write_to = *reinterpret_cast<const ProbPointer*>(current_ + sizeof(WordIndex));
base[write_to.array][write_to.index] += weights.backoff;
}
backing_.reset();
}
void Apply(float *const *const base, RecordReader &reader) {
FinishedAdding();
if (current_ == allocated_) return;
// We'll also use the same buffer to record messages to blanks that they extend.
WordIndex *extend_out = reinterpret_cast<WordIndex*>(current_);
const unsigned char order = (entry_size_ - sizeof(ProbPointer)) / sizeof(WordIndex);
for (reader.Rewind(); reader && (current_ != allocated_); ) {
switch (Compare(order, reader.Data(), current_)) {
case -1:
++reader;
break;
case 1:
// Message but nobody to receive it. Write it down at the beginning of the buffer so we can inform this blank that it extends.
for (const WordIndex *w = reinterpret_cast<const WordIndex *>(current_); w != reinterpret_cast<const WordIndex *>(current_) + order; ++w, ++extend_out) *extend_out = *w;
current_ += entry_size_;
break;
case 0:
float &backoff = reinterpret_cast<ProbBackoff*>((uint8_t*)reader.Data() + order * sizeof(WordIndex))->backoff;
if (!HasExtension(backoff)) {
backoff = kExtensionBackoff;
reader.Overwrite(&backoff, sizeof(float));
} else {
const ProbPointer &write_to = *reinterpret_cast<const ProbPointer*>(current_ + entry_size_ - sizeof(ProbPointer));
base[write_to.array][write_to.index] += backoff;
}
current_ += entry_size_;
break;
}
}
// Now this is a list of blanks that extend right.
entry_size_ = sizeof(WordIndex) * order;
Resize(sizeof(WordIndex) * (extend_out - (const WordIndex*)backing_.get()));
current_ = (uint8_t*)backing_.get();
}
// Call after Apply
bool Extends(unsigned char order, const WordIndex *words) {
if (current_ == allocated_) return false;
assert(order * sizeof(WordIndex) == entry_size_);
while (true) {
switch(Compare(order, words, current_)) {
case 1:
current_ += entry_size_;
if (current_ == allocated_) return false;
break;
case -1:
return false;
case 0:
return true;
}
}
}
private:
void FinishedAdding() {
Resize(current_ - (uint8_t*)backing_.get());
// Sort requests in same order as files.
std::sort(
util::SizedIterator(util::SizedProxy(backing_.get(), entry_size_)),
util::SizedIterator(util::SizedProxy(current_, entry_size_)),
util::SizedCompare<EntryCompare>(EntryCompare((entry_size_ - sizeof(ProbPointer)) / sizeof(WordIndex))));
current_ = (uint8_t*)backing_.get();
}
void Resize(std::size_t to) {
std::size_t current = current_ - (uint8_t*)backing_.get();
backing_.call_realloc(to);
current_ = (uint8_t*)backing_.get() + current;
allocated_ = (uint8_t*)backing_.get() + to;
}
util::scoped_malloc backing_;
uint8_t *current_, *allocated_;
std::size_t entry_size_;
};
const float kBadProb = std::numeric_limits<float>::infinity();
class SRISucks {
public:
SRISucks() {
for (BackoffMessages *i = messages_; i != messages_ + KENLM_MAX_ORDER - 1; ++i)
i->Init(sizeof(ProbPointer) + sizeof(WordIndex) * (i - messages_ + 1));
}
void Send(unsigned char begin, unsigned char order, const WordIndex *to, float prob_basis) {
assert(prob_basis != kBadProb);
ProbPointer pointer;
pointer.array = order - 1;
pointer.index = values_[order - 1].size();
for (unsigned char i = begin; i < order; ++i) {
messages_[i - 1].Add(to, pointer);
}
values_[order - 1].push_back(prob_basis);
}
void ObtainBackoffs(unsigned char total_order, FILE *unigram_file, RecordReader *reader) {
for (unsigned char i = 0; i < KENLM_MAX_ORDER - 1; ++i) {
it_[i] = values_[i].empty() ? NULL : &*values_[i].begin();
}
messages_[0].Apply(it_, unigram_file);
BackoffMessages *messages = messages_ + 1;
const RecordReader *end = reader + total_order - 2 /* exclude unigrams and longest order */;
for (; reader != end; ++messages, ++reader) {
messages->Apply(it_, *reader);
}
}
ProbBackoff GetBlank(unsigned char total_order, unsigned char order, const WordIndex *indices) {
assert(order > 1);
ProbBackoff ret;
ret.prob = *(it_[order - 1]++);
ret.backoff = ((order != total_order - 1) && messages_[order - 1].Extends(order, indices)) ? kExtensionBackoff : kNoExtensionBackoff;
return ret;
}
const std::vector<float> &Values(unsigned char order) const {
return values_[order - 1];
}
private:
// This used to be one array. Then I needed to separate it by order for quantization to work.
std::vector<float> values_[KENLM_MAX_ORDER - 1];
BackoffMessages messages_[KENLM_MAX_ORDER - 1];
float *it_[KENLM_MAX_ORDER - 1];
};
class FindBlanks {
public:
FindBlanks(unsigned char order, const ProbBackoff *unigrams, SRISucks &messages)
: counts_(order), unigrams_(unigrams), sri_(messages) {}
float UnigramProb(WordIndex index) const {
return unigrams_[index].prob;
}
void Unigram(WordIndex /*index*/) {
++counts_[0];
}
void MiddleBlank(const unsigned char order, const WordIndex *indices, unsigned char lower, float prob_basis) {
sri_.Send(lower, order, indices + 1, prob_basis);
++counts_[order - 1];
}
void Middle(const unsigned char order, const void * /*data*/) {
++counts_[order - 1];
}
void Longest(const void * /*data*/) {
++counts_.back();
}
const std::vector<uint64_t> &Counts() const {
return counts_;
}
private:
std::vector<uint64_t> counts_;
const ProbBackoff *unigrams_;
SRISucks &sri_;
};
// Phase to actually write n-grams to the trie.
template <class Quant, class Bhiksha> class WriteEntries {
public:
WriteEntries(RecordReader *contexts, const Quant &quant, UnigramValue *unigrams, BitPackedMiddle<Bhiksha> *middle, BitPackedLongest &longest, unsigned char order, SRISucks &sri) :
contexts_(contexts),
quant_(quant),
unigrams_(unigrams),
middle_(middle),
longest_(longest),
bigram_pack_((order == 2) ? static_cast<BitPacked&>(longest_) : static_cast<BitPacked&>(*middle_)),
order_(order),
sri_(sri) {}
float UnigramProb(WordIndex index) const { return unigrams_[index].weights.prob; }
void Unigram(WordIndex word) {
unigrams_[word].next = bigram_pack_.InsertIndex();
}
void MiddleBlank(const unsigned char order, const WordIndex *indices, unsigned char /*lower*/, float /*prob_base*/) {
ProbBackoff weights = sri_.GetBlank(order_, order, indices);
typename Quant::MiddlePointer(quant_, order - 2, middle_[order - 2].Insert(indices[order - 1])).Write(weights.prob, weights.backoff);
}
void Middle(const unsigned char order, const void *data) {
RecordReader &context = contexts_[order - 1];
const WordIndex *words = reinterpret_cast<const WordIndex*>(data);
ProbBackoff weights = *reinterpret_cast<const ProbBackoff*>(words + order);
if (context && !memcmp(data, context.Data(), sizeof(WordIndex) * order)) {
SetExtension(weights.backoff);
++context;
}
typename Quant::MiddlePointer(quant_, order - 2, middle_[order - 2].Insert(words[order - 1])).Write(weights.prob, weights.backoff);
}
void Longest(const void *data) {
const WordIndex *words = reinterpret_cast<const WordIndex*>(data);
typename Quant::LongestPointer(quant_, longest_.Insert(words[order_ - 1])).Write(reinterpret_cast<const Prob*>(words + order_)->prob);
}
private:
RecordReader *contexts_;
const Quant &quant_;
UnigramValue *const unigrams_;
BitPackedMiddle<Bhiksha> *const middle_;
BitPackedLongest &longest_;
BitPacked &bigram_pack_;
const unsigned char order_;
SRISucks &sri_;
};
struct Gram {
Gram(const WordIndex *in_begin, unsigned char order) : begin(in_begin), end(in_begin + order) {}
const WordIndex *begin, *end;
// For queue, this is the direction we want.
bool operator<(const Gram &other) const {
return std::lexicographical_compare(other.begin, other.end, begin, end);
}
};
template <class Doing> class BlankManager {
public:
BlankManager(unsigned char total_order, Doing &doing) : total_order_(total_order), been_length_(0), doing_(doing) {
for (float *i = basis_; i != basis_ + KENLM_MAX_ORDER - 1; ++i) *i = kBadProb;
}
void Visit(const WordIndex *to, unsigned char length, float prob) {
basis_[length - 1] = prob;
unsigned char overlap = std::min<unsigned char>(length - 1, been_length_);
const WordIndex *cur;
WordIndex *pre;
for (cur = to, pre = been_; cur != to + overlap; ++cur, ++pre) {
if (*pre != *cur) break;
}
if (cur == to + length - 1) {
*pre = *cur;
been_length_ = length;
return;
}
// There are blanks to insert starting with order blank.
unsigned char blank = cur - to + 1;
UTIL_THROW_IF(blank == 1, FormatLoadException, "Missing a unigram that appears as context.");
const float *lower_basis;
for (lower_basis = basis_ + blank - 2; *lower_basis == kBadProb; --lower_basis) {}
unsigned char based_on = lower_basis - basis_ + 1;
for (; cur != to + length - 1; ++blank, ++cur, ++pre) {
assert(*lower_basis != kBadProb);
doing_.MiddleBlank(blank, to, based_on, *lower_basis);
*pre = *cur;
// Mark that the probability is a blank so it shouldn't be used as the basis for a later n-gram.
basis_[blank - 1] = kBadProb;
}
*pre = *cur;
been_length_ = length;
}
private:
const unsigned char total_order_;
WordIndex been_[KENLM_MAX_ORDER];
unsigned char been_length_;
float basis_[KENLM_MAX_ORDER];
Doing &doing_;
};
template <class Doing> void RecursiveInsert(const unsigned char total_order, const WordIndex unigram_count, RecordReader *input, std::ostream *progress_out, const char *message, Doing &doing) {
util::ErsatzProgress progress(unigram_count + 1, progress_out, message);
WordIndex unigram = 0;
std::priority_queue<Gram> grams;
if (unigram_count) grams.push(Gram(&unigram, 1));
for (unsigned char i = 2; i <= total_order; ++i) {
if (input[i-2]) grams.push(Gram(reinterpret_cast<const WordIndex*>(input[i-2].Data()), i));
}
BlankManager<Doing> blank(total_order, doing);
while (!grams.empty()) {
Gram top = grams.top();
grams.pop();
unsigned char order = top.end - top.begin;
if (order == 1) {
blank.Visit(&unigram, 1, doing.UnigramProb(unigram));
doing.Unigram(unigram);
progress.Set(unigram);
if (++unigram < unigram_count) grams.push(top);
} else {
if (order == total_order) {
blank.Visit(top.begin, order, reinterpret_cast<const Prob*>(top.end)->prob);
doing.Longest(top.begin);
} else {
blank.Visit(top.begin, order, reinterpret_cast<const ProbBackoff*>(top.end)->prob);
doing.Middle(order, top.begin);
}
RecordReader &reader = input[order - 2];
if (++reader) grams.push(top);
}
}
}
void SanityCheckCounts(const std::vector<uint64_t> &initial, const std::vector<uint64_t> &fixed) {
if (fixed[0] != initial[0]) UTIL_THROW(util::Exception, "Unigram count should be constant but initial is " << initial[0] << " and recounted is " << fixed[0]);
if (fixed.back() != initial.back()) UTIL_THROW(util::Exception, "Longest count should be constant but it changed from " << initial.back() << " to " << fixed.back());
for (unsigned char i = 0; i < initial.size(); ++i) {
if (fixed[i] < initial[i]) UTIL_THROW(util::Exception, "Counts came out lower than expected. This shouldn't happen");
}
}
template <class Quant> void TrainQuantizer(uint8_t order, uint64_t count, const std::vector<float> &additional, RecordReader &reader, util::ErsatzProgress &progress, Quant &quant) {
std::vector<float> probs(additional), backoffs;
probs.reserve(count + additional.size());
backoffs.reserve(count);
for (reader.Rewind(); reader; ++reader) {
const ProbBackoff &weights = *reinterpret_cast<const ProbBackoff*>(reinterpret_cast<const uint8_t*>(reader.Data()) + sizeof(WordIndex) * order);
probs.push_back(weights.prob);
if (weights.backoff != 0.0) backoffs.push_back(weights.backoff);
++progress;
}
quant.Train(order, probs, backoffs);
}
template <class Quant> void TrainProbQuantizer(uint8_t order, uint64_t count, RecordReader &reader, util::ErsatzProgress &progress, Quant &quant) {
std::vector<float> probs, backoffs;
probs.reserve(count);
for (reader.Rewind(); reader; ++reader) {
const Prob &weights = *reinterpret_cast<const Prob*>(reinterpret_cast<const uint8_t*>(reader.Data()) + sizeof(WordIndex) * order);
probs.push_back(weights.prob);
++progress;
}
quant.TrainProb(order, probs);
}
void PopulateUnigramWeights(FILE *file, WordIndex unigram_count, RecordReader &contexts, UnigramValue *unigrams) {
// Fill unigram probabilities.
try {
rewind(file);
for (WordIndex i = 0; i < unigram_count; ++i) {
ReadOrThrow(file, &unigrams[i].weights, sizeof(ProbBackoff));
if (contexts && *reinterpret_cast<const WordIndex*>(contexts.Data()) == i) {
SetExtension(unigrams[i].weights.backoff);
++contexts;
}
}
} catch (util::Exception &e) {
e << " while re-reading unigram probabilities";
throw;
}
}
} // namespace
template <class Quant, class Bhiksha> void BuildTrie(SortedFiles &files, std::vector<uint64_t> &counts, const Config &config, TrieSearch<Quant, Bhiksha> &out, Quant &quant, SortedVocabulary &vocab, BinaryFormat &backing) {
RecordReader inputs[KENLM_MAX_ORDER - 1];
RecordReader contexts[KENLM_MAX_ORDER - 1];
for (unsigned char i = 2; i <= counts.size(); ++i) {
inputs[i-2].Init(files.Full(i), i * sizeof(WordIndex) + (i == counts.size() ? sizeof(Prob) : sizeof(ProbBackoff)));
contexts[i-2].Init(files.Context(i), (i-1) * sizeof(WordIndex));
}
SRISucks sri;
std::vector<uint64_t> fixed_counts;
util::scoped_FILE unigram_file;
util::scoped_fd unigram_fd(files.StealUnigram());
{
util::scoped_memory unigrams;
MapRead(util::POPULATE_OR_READ, unigram_fd.get(), 0, counts[0] * sizeof(ProbBackoff), unigrams);
FindBlanks finder(counts.size(), reinterpret_cast<const ProbBackoff*>(unigrams.get()), sri);
RecursiveInsert(counts.size(), counts[0], inputs, config.ProgressMessages(), "Identifying n-grams omitted by SRI", finder);
fixed_counts = finder.Counts();
}
unigram_file.reset(util::FDOpenOrThrow(unigram_fd));
for (const RecordReader *i = inputs; i != inputs + counts.size() - 2; ++i) {
if (*i) UTIL_THROW(FormatLoadException, "There's a bug in the trie implementation: the " << (i - inputs + 2) << "-gram table did not complete reading");
}
SanityCheckCounts(counts, fixed_counts);
counts = fixed_counts;
sri.ObtainBackoffs(counts.size(), unigram_file.get(), inputs);
void *vocab_relocate;
void *search_base = backing.GrowForSearch(TrieSearch<Quant, Bhiksha>::Size(fixed_counts, config), vocab.UnkCountChangePadding(), vocab_relocate);
vocab.Relocate(vocab_relocate);
out.SetupMemory(reinterpret_cast<uint8_t*>(search_base), fixed_counts, config);
for (unsigned char i = 2; i <= counts.size(); ++i) {
inputs[i-2].Rewind();
}
if (Quant::kTrain) {
util::ErsatzProgress progress(std::accumulate(counts.begin() + 1, counts.end(), 0),
config.ProgressMessages(), "Quantizing");
for (unsigned char i = 2; i < counts.size(); ++i) {
TrainQuantizer(i, counts[i-1], sri.Values(i), inputs[i-2], progress, quant);
}
TrainProbQuantizer(counts.size(), counts.back(), inputs[counts.size() - 2], progress, quant);
quant.FinishedLoading(config);
}
UnigramValue *unigrams = out.unigram_.Raw();
PopulateUnigramWeights(unigram_file.get(), counts[0], contexts[0], unigrams);
unigram_file.reset();
for (unsigned char i = 2; i <= counts.size(); ++i) {
inputs[i-2].Rewind();
}
// Fill entries except unigram probabilities.
{
WriteEntries<Quant, Bhiksha> writer(contexts, quant, unigrams, out.middle_begin_, out.longest_, counts.size(), sri);
RecursiveInsert(counts.size(), counts[0], inputs, config.ProgressMessages(), "Writing trie", writer);
// Write the last unigram entry, which is the end pointer for the bigrams.
writer.Unigram(counts[0]);
}
// Do not disable this error message or else too little state will be returned. Both WriteEntries::Middle and returning state based on found n-grams will need to be fixed to handle this situation.
for (unsigned char order = 2; order <= counts.size(); ++order) {
const RecordReader &context = contexts[order - 2];
if (context) {
FormatLoadException e;
e << "A " << static_cast<unsigned int>(order) << "-gram has context";
const WordIndex *ctx = reinterpret_cast<const WordIndex*>(context.Data());
for (const WordIndex *i = ctx; i != ctx + order - 1; ++i) {
e << ' ' << *i;
}
e << " so this context must appear in the model as a " << static_cast<unsigned int>(order - 1) << "-gram but it does not";
throw e;
}
}
/* Set ending offsets so the last entry will be sized properly */
// Last entry for unigrams was already set.
if (out.middle_begin_ != out.middle_end_) {
for (typename TrieSearch<Quant, Bhiksha>::Middle *i = out.middle_begin_; i != out.middle_end_ - 1; ++i) {
i->FinishedLoading((i+1)->InsertIndex(), config);
}
(out.middle_end_ - 1)->FinishedLoading(out.longest_.InsertIndex(), config);
}
}
template <class Quant, class Bhiksha> uint8_t *TrieSearch<Quant, Bhiksha>::SetupMemory(uint8_t *start, const std::vector<uint64_t> &counts, const Config &config) {
quant_.SetupMemory(start, counts.size(), config);
start += Quant::Size(counts.size(), config);
unigram_.Init(start);
start += Unigram::Size(counts[0]);
FreeMiddles();
middle_begin_ = static_cast<Middle*>(malloc(sizeof(Middle) * (counts.size() - 2)));
middle_end_ = middle_begin_ + (counts.size() - 2);
std::vector<uint8_t*> middle_starts(counts.size() - 2);
for (unsigned char i = 2; i < counts.size(); ++i) {
middle_starts[i-2] = start;
start += Middle::Size(Quant::MiddleBits(config), counts[i-1], counts[0], counts[i], config);
}
// Crazy backwards thing so we initialize using pointers to ones that have already been initialized
for (unsigned char i = counts.size() - 1; i >= 2; --i) {
// use "placement new" syntax to initalize Middle in an already-allocated memory location
new (middle_begin_ + i - 2) Middle(
middle_starts[i-2],
quant_.MiddleBits(config),
counts[i-1],
counts[0],
counts[i],
(i == counts.size() - 1) ? static_cast<const BitPacked&>(longest_) : static_cast<const BitPacked &>(middle_begin_[i-1]),
config);
}
longest_.Init(start, quant_.LongestBits(config), counts[0]);
return start + Longest::Size(Quant::LongestBits(config), counts.back(), counts[0]);
}
template <class Quant, class Bhiksha> void TrieSearch<Quant, Bhiksha>::InitializeFromARPA(const char *file, util::FilePiece &f, std::vector<uint64_t> &counts, const Config &config, SortedVocabulary &vocab, BinaryFormat &backing) {
std::string temporary_prefix;
if (config.temporary_directory_prefix) {
temporary_prefix = config.temporary_directory_prefix;
} else if (config.write_mmap) {
temporary_prefix = config.write_mmap;
} else {
temporary_prefix = file;
}
// At least 1MB sorting memory.
SortedFiles sorted(config, f, counts, std::max<size_t>(config.building_memory, 1048576), temporary_prefix, vocab);
BuildTrie(sorted, counts, config, *this, quant_, vocab, backing);
}
template class TrieSearch<DontQuantize, DontBhiksha>;
template class TrieSearch<DontQuantize, ArrayBhiksha>;
template class TrieSearch<SeparatelyQuantize, DontBhiksha>;
template class TrieSearch<SeparatelyQuantize, ArrayBhiksha>;
} // namespace trie
} // namespace ngram
} // namespace lm
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