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#ifndef _NS_H_
#define _NS_H_
#include <string>
#include <vector>
#include <map>
#include <boost/shared_ptr.hpp>
#include "wordid.h"
class EvaluationMetric;
class SufficientStats {
public:
SufficientStats() : evaluation_metric() {}
explicit SufficientStats(const std::string& encoded);
explicit SufficientStats(const EvaluationMetric* s) : evaluation_metric(s) {}
SufficientStats(const EvaluationMetric* s, const std::vector<float>& f) :
evaluation_metric(s), fields(f) {}
SufficientStats& operator+=(const SufficientStats& delta) {
if (delta.evaluation_metric) evaluation_metric = delta.evaluation_metric;
if (fields.size() != delta.fields.size())
fields.resize(std::max(fields.size(), delta.fields.size()));
for (unsigned i = 0; i < delta.fields.size(); ++i)
fields[i] += delta.fields[i];
return *this;
}
SufficientStats& operator-=(const SufficientStats& delta) {
if (delta.evaluation_metric) evaluation_metric = delta.evaluation_metric;
if (fields.size() != delta.fields.size())
fields.resize(std::max(fields.size(), delta.fields.size()));
for (unsigned i = 0; i < delta.fields.size(); ++i)
fields[i] -= delta.fields[i];
return *this;
}
SufficientStats& operator*=(const double& scalar) {
for (unsigned i = 0; i < fields.size(); ++i)
fields[i] *= scalar;
return *this;
}
SufficientStats& operator/=(const double& scalar) {
for (unsigned i = 0; i < fields.size(); ++i)
fields[i] /= scalar;
return *this;
}
bool operator==(const SufficientStats& other) const {
return other.fields == fields;
}
size_t size() const { return fields.size(); }
float operator[](size_t i) const {
if (i < fields.size()) return fields[i];
return 0;
}
void Encode(std::string* out) const;
const EvaluationMetric* evaluation_metric;
std::vector<float> fields;
};
inline const SufficientStats& operator+(const SufficientStats& a, const SufficientStats& b) {
SufficientStats res(a);
return res += b;
}
inline const SufficientStats& operator-(const SufficientStats& a, const SufficientStats& b) {
SufficientStats res(a);
return res -= b;
}
struct SegmentEvaluator {
virtual ~SegmentEvaluator();
virtual void Evaluate(const std::vector<WordID>& hyp, SufficientStats* out) const = 0;
};
// Instructions for implementing a new metric
// Override MetricId() and give the metric a unique string name (no spaces)
// To Instance(), add something that creates the metric
// Implement ONE of the following:
// 1) void ComputeSufficientStatistics(const std::vector<std::vector<WordID> >& refs, SufficientStats* out) const;
// 2) a new SegmentEvaluator class AND CreateSegmentEvaluator(const std::vector<std::vector<WordID> >& refs) const;
// The later (#2) is only used when it is necessary to precompute per-segment data from a set of refs
// Implement ComputeScore(const SufficientStats& stats) const;
class EvaluationMetric {
public:
static EvaluationMetric* Instance(const std::string& metric_id = "IBM_BLEU");
protected:
EvaluationMetric(const std::string& id) : name_(id) {}
virtual ~EvaluationMetric();
public:
const std::string& MetricId() const { return name_; }
virtual float ComputeScore(const SufficientStats& stats) const = 0;
virtual boost::shared_ptr<SegmentEvaluator> CreateSegmentEvaluator(const std::vector<std::vector<WordID> >& refs) const;
virtual void ComputeSufficientStatistics(const std::vector<WordID>& hyp,
const std::vector<std::vector<WordID> >& refs,
SufficientStats* out) const;
private:
static std::map<std::string, EvaluationMetric*> instances_;
const std::string name_;
};
#endif
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