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/*
* MiraWeightVector.h
* kbmira - k-best Batch MIRA
*
* A self-averaging weight-vector. Good for
* perceptron learning as well.
*
*/
#ifndef MERT_MIRA_WEIGHT_VECTOR_H
#define MERT_MIRA_WEIGHT_VECTOR_H
#include <vector>
#include <iostream>
#include "MiraFeatureVector.h"
namespace MosesTuning
{
class AvgWeightVector;
class MiraWeightVector
{
public:
/**
* Constructor, initializes to the zero vector
*/
MiraWeightVector();
/**
* Constructor with provided initial vector
* \param init Initial feature values
*/
MiraWeightVector(const std::vector<ValType>& init);
/**
* Update a the model
* \param fv Feature vector to be added to the weights
* \param tau FV will be scaled by this value before update
*/
void update(const MiraFeatureVector& fv, float tau);
/**
* Perform an empty update (affects averaging)
*/
void tick();
/**
* Score a feature vector according to the model
* \param fv Feature vector to be scored
*/
ValType score(const MiraFeatureVector& fv) const;
/**
* Squared norm of the weight vector
*/
ValType sqrNorm() const;
/**
* Return an averaged view of this weight vector
*/
AvgWeightVector avg();
/**
* Convert to sparse vector, interpreting all features as sparse. Only used by hgmira.
**/
void ToSparse(SparseVector* sparse, size_t denseSize) const;
friend class AvgWeightVector;
friend std::ostream& operator<<(std::ostream& o, const MiraWeightVector& e);
private:
/**
* Updates a weight and lazily updates its total
*/
void update(std::size_t index, ValType delta);
/**
* Make sure everyone's total is up-to-date
*/
void fixTotals();
/**
* Helper to handle out-of-range weights
*/
ValType weight(std::size_t index) const;
std::vector<ValType> m_weights;
std::vector<ValType> m_totals;
std::vector<std::size_t> m_lastUpdated;
std::size_t m_numUpdates;
};
/**
* Averaged view of a weight vector
*/
class AvgWeightVector
{
public:
AvgWeightVector(const MiraWeightVector& wv);
ValType score(const MiraFeatureVector& fv) const;
ValType weight(std::size_t index) const;
std::size_t size() const;
void ToSparse(SparseVector* sparse, size_t num_dense) const;
private:
const MiraWeightVector& m_wv;
};
// --Emacs trickery--
// Local Variables:
// mode:c++
// c-basic-offset:2
// End:
}
#endif // MERT_WEIGHT_VECTOR_H
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