/usr/include/ngram/ngram-context-prune.h is in libngram-dev 1.3.2-3.
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// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// Copyright 2005-2016 Brian Roark and Google, Inc.
// Context pruning style model shrinking derived class.
#ifndef NGRAM_NGRAM_CONTEXT_PRUNE_H_
#define NGRAM_NGRAM_CONTEXT_PRUNE_H_
#include <string>
#include <vector>
#include <ngram/ngram-context.h>
#include <ngram/ngram-count-prune.h>
#include <ngram/ngram-relentropy.h>
#include <ngram/ngram-seymore-shrink.h>
#include <ngram/ngram-shrink.h>
namespace ngram {
// Context-restricting pruning
class NGramContextPrune : public NGramShrink<StdArc> {
public:
// Constructs an NGramShrink object, including an NGramModel and
// parameters. This version is passed a context pattern string; see
// 'ngram-context.h' for meaning of the context specification. The
// specified contexts will NOT be pruned from the model; all others
// will be (where possible to maintain a well-formed LM).
explicit NGramContextPrune(StdMutableFst *infst,
const string &context_pattern = "",
int shrink_opt = 0, double tot_uni = -1.0,
Label backoff_label = 0,
double norm_eps = kNormEps,
bool check_consistency = false)
// shrink_opt must be less than 2 for context pruning
: NGramShrink<StdArc>(infst, shrink_opt < 2 ? shrink_opt : 0, tot_uni,
backoff_label, norm_eps, true),
context_(context_pattern, HiOrder()) {}
// Constructs an NGramShrink object, including an NGramModel and
// parameters. This version is given begin and end context
// vectors; see 'ngram-context.h' for meaning of the context
// specification. The specified contexts will NOT be pruned from
// the model; all others will be (where possible to maintaine a
// well-formed LM).
NGramContextPrune(StdMutableFst *infst,
const std::vector<Label> &context_begin,
const std::vector<Label> &context_end, int shrink_opt = 0,
double tot_uni = -1.0, Label backoff_label = 0,
double norm_eps = kNormEps, bool check_consistency = false)
// shrink_opt must be less than 2 for context pruning
: NGramShrink(infst, shrink_opt < 2 ? shrink_opt : 0, tot_uni,
backoff_label, norm_eps, true),
context_(context_begin, context_end, HiOrder()) {}
~NGramContextPrune() override {}
// Shrinks n-gram model, based on initialized parameters
bool ShrinkNGramModel() {
return NGramShrink<StdArc>::ShrinkNGramModel(false);
}
protected:
// Gives the pruning threshold
double GetTheta(StateId state) const override { return 0.0; }
double ShrinkScore(const ShrinkStateStats &state,
const ShrinkArcStats &arc) const override {
const std::vector<Label> &ngram = StateNGram(state.state);
return context_.HasContext(ngram) ? 1.0 : -1.0;
}
private:
NGramContext context_; // context specification
};
// Joint context-restricting and count pruning
class NGramContextCountPrune : public NGramCountPrune {
public:
NGramContextCountPrune(StdMutableFst *infst,
const string &count_pattern,
string context_pattern, int shrink_opt = 0,
double tot_uni = -1.0, Label backoff_label = 0,
double norm_eps = kNormEps,
bool check_consistency = false)
// shrink_opt must be less than 2 for context pruning
: NGramCountPrune(infst, count_pattern, shrink_opt < 2 ? shrink_opt : 0,
tot_uni, backoff_label, norm_eps, true),
context_(context_pattern, HiOrder()) {}
NGramContextCountPrune(StdMutableFst *infst,
const std::vector<double> &count_minimums,
const std::vector<Label> &context_begin,
const std::vector<Label> &context_end,
int shrink_opt = 0, double tot_uni = -1.0,
Label backoff_label = 0, double norm_eps = kNormEps,
bool check_consistency = false)
// shrink_opt must be less than 2 for context pruning
: NGramCountPrune(infst, count_minimums, shrink_opt < 2 ? shrink_opt : 0,
tot_uni, backoff_label, norm_eps, true),
context_(context_begin, context_end, HiOrder()) {}
~NGramContextCountPrune() override {}
// Shrinks n-gram model, based on initialized parameters
bool ShrinkNGramModel() { return NGramCountPrune::ShrinkNGramModel(); }
protected:
double ShrinkScore(const ShrinkStateStats &state,
const ShrinkArcStats &arc) const override {
const std::vector<Label> &ngram = StateNGram(state.state);
if (context_.HasContext(ngram)) {
return NGramCountPrune::ShrinkScore(state, arc);
} else {
return GetTheta(state.state) - 1.0;
}
}
private:
NGramContext context_; // context specification
NGramContextCountPrune(const NGramContextCountPrune &) = delete;
};
// Joint context-restricting and relative entropy pruning
class NGramContextRelEntropy : public NGramRelEntropy {
public:
NGramContextRelEntropy(StdMutableFst *infst, double theta,
const string &context_pattern, int shrink_opt = 0,
double tot_uni = -1.0, Label backoff_label = 0,
double norm_eps = kNormEps,
bool check_consistency = false)
// shrink_opt must be less than 2 for context pruning
: NGramRelEntropy(infst, theta, shrink_opt < 2 ? shrink_opt : 0, tot_uni,
backoff_label, norm_eps, true),
context_(context_pattern, HiOrder()) {}
NGramContextRelEntropy(StdMutableFst *infst, double theta,
const std::vector<Label> &context_begin,
const std::vector<Label> &context_end,
int shrink_opt = 0, double tot_uni = -1.0,
Label backoff_label = 0, double norm_eps = kNormEps,
bool check_consistency = false)
// shrink_opt must be less than 2 for context pruning
: NGramRelEntropy(infst, theta, shrink_opt < 2 ? shrink_opt : 0, tot_uni,
backoff_label, norm_eps, true),
context_(context_begin, context_end, HiOrder()) {}
~NGramContextRelEntropy() override {}
// Shrinks n-gram model, based on initialized parameters
bool ShrinkNGramModel() { return NGramRelEntropy::ShrinkNGramModel(); }
protected:
double ShrinkScore(const ShrinkStateStats &state,
const ShrinkArcStats &arc) const override {
const std::vector<Label> &ngram = StateNGram(state.state);
if (context_.HasContext(ngram)) {
return NGramRelEntropy::ShrinkScore(state, arc);
} else {
return GetTheta(state.state) - 1.0;
}
}
private:
NGramContext context_; // context specification
NGramContextRelEntropy(const NGramContextRelEntropy &) = delete;
NGramContextRelEntropy &operator=(const NGramContextRelEntropy &) = delete;
};
// Joint context-restricting and SeymoreShrink-Rosenfeld pruning
class NGramContextSeymoreShrink : public NGramSeymoreShrink {
public:
NGramContextSeymoreShrink(StdMutableFst *infst, double theta,
const string &context_pattern, int shrink_opt = 0,
double tot_uni = -1.0, Label backoff_label = 0,
double norm_eps = kNormEps,
bool check_consistency = false)
// shrink_opt must be less than 2 for context pruning
: NGramSeymoreShrink(infst, theta, shrink_opt < 2 ? shrink_opt : 0,
tot_uni, backoff_label, norm_eps, true),
context_(context_pattern, HiOrder()) {}
NGramContextSeymoreShrink(StdMutableFst *infst, double theta,
const std::vector<Label> &context_begin,
const std::vector<Label> &context_end,
int shrink_opt = 0, double tot_uni = -1.0,
Label backoff_label = 0, double norm_eps = kNormEps,
bool check_consistency = false)
// shrink_opt must be less than 2 for context pruning
: NGramSeymoreShrink(infst, theta, shrink_opt < 2 ? shrink_opt : 0,
tot_uni, backoff_label, norm_eps, true),
context_(context_begin, context_end, HiOrder()) {}
~NGramContextSeymoreShrink() override {}
// Shrinks n-gram model, based on initialized parameters
bool ShrinkNGramModel() { return NGramSeymoreShrink::ShrinkNGramModel(); }
protected:
double ShrinkScore(const ShrinkStateStats &state,
const ShrinkArcStats &arc) const override {
const std::vector<Label> &ngram = StateNGram(state.state);
if (context_.HasContext(ngram)) {
return NGramSeymoreShrink::ShrinkScore(state, arc);
} else {
return GetTheta(state.state) - 1.0;
}
}
private:
NGramContext context_; // context specification
NGramContextSeymoreShrink(const NGramContextSeymoreShrink &) = delete;
NGramContextSeymoreShrink
&operator=(const NGramContextSeymoreShrink &) = delete;
};
} // namespace ngram
#endif // NGRAM_NGRAM_CONTEXT_PRUNE_H_
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