mirror of
https://github.com/moses-smt/mosesdecoder.git
synced 2024-12-27 14:05:29 +03:00
100 lines
3.5 KiB
C++
100 lines
3.5 KiB
C++
#include "lm/builder/interpolate.hh"
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#include "lm/builder/hash_gamma.hh"
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#include "lm/builder/joint_order.hh"
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#include "lm/builder/ngram_stream.hh"
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#include "lm/builder/sort.hh"
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#include "lm/lm_exception.hh"
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#include "util/fixed_array.hh"
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#include "util/murmur_hash.hh"
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#include <assert.h>
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namespace lm { namespace builder {
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namespace {
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class Callback {
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public:
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Callback(float uniform_prob, const util::stream::ChainPositions &backoffs, const std::vector<uint64_t> &prune_thresholds)
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: backoffs_(backoffs.size()), probs_(backoffs.size() + 2), prune_thresholds_(prune_thresholds) {
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probs_[0] = uniform_prob;
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for (std::size_t i = 0; i < backoffs.size(); ++i) {
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backoffs_.push_back(backoffs[i]);
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}
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}
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~Callback() {
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for (std::size_t i = 0; i < backoffs_.size(); ++i) {
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if(prune_thresholds_[i + 1] > 0)
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while(backoffs_[i])
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++backoffs_[i];
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if (backoffs_[i]) {
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std::cerr << "Backoffs do not match for order " << (i + 1) << std::endl;
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abort();
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}
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}
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}
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void Enter(unsigned order_minus_1, NGram &gram) {
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Payload &pay = gram.Value();
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pay.complete.prob = pay.uninterp.prob + pay.uninterp.gamma * probs_[order_minus_1];
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probs_[order_minus_1 + 1] = pay.complete.prob;
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pay.complete.prob = log10(pay.complete.prob);
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if (order_minus_1 < backoffs_.size() && *(gram.end() - 1) != kUNK && *(gram.end() - 1) != kEOS) {
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// This skips over ngrams if backoffs have been exhausted.
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if(!backoffs_[order_minus_1]) {
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pay.complete.backoff = 0.0;
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return;
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}
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if(prune_thresholds_[order_minus_1 + 1] > 0) {
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//Compute hash value for current context
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uint64_t current_hash = util::MurmurHashNative(gram.begin(), gram.Order() * sizeof(WordIndex));
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const HashGamma *hashed_backoff = static_cast<const HashGamma*>(backoffs_[order_minus_1].Get());
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while(current_hash != hashed_backoff->hash_value && ++backoffs_[order_minus_1])
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hashed_backoff = static_cast<const HashGamma*>(backoffs_[order_minus_1].Get());
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if(current_hash == hashed_backoff->hash_value) {
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pay.complete.backoff = log10(hashed_backoff->gamma);
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++backoffs_[order_minus_1];
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} else {
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// Has been pruned away so it is not a context anymore
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pay.complete.backoff = 0.0;
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}
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} else {
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pay.complete.backoff = log10(*static_cast<const float*>(backoffs_[order_minus_1].Get()));
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++backoffs_[order_minus_1];
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}
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} else {
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// Not a context.
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pay.complete.backoff = 0.0;
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}
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}
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void Exit(unsigned, const NGram &) const {}
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private:
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util::FixedArray<util::stream::Stream> backoffs_;
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std::vector<float> probs_;
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const std::vector<uint64_t>& prune_thresholds_;
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};
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} // namespace
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Interpolate::Interpolate(uint64_t vocab_size, const util::stream::ChainPositions &backoffs, const std::vector<uint64_t>& prune_thresholds)
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: uniform_prob_(1.0 / static_cast<float>(vocab_size)), // Includes <unk> but excludes <s>.
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backoffs_(backoffs),
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prune_thresholds_(prune_thresholds) {}
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// perform order-wise interpolation
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void Interpolate::Run(const util::stream::ChainPositions &positions) {
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assert(positions.size() == backoffs_.size() + 1);
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Callback callback(uniform_prob_, backoffs_, prune_thresholds_);
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JointOrder<Callback, SuffixOrder>(positions, callback);
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}
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}} // namespaces
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