libshogun-dev 3.2.0-7.5 / usr / include / shogun / features / HashedWDFeatures.h

/*
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * Written (W) 2010 Soeren Sonnenburg
 * Copyright (C) 2010 Berlin Institute of Technology
 */

#ifndef _HASHEDWDFEATURES_H___
#define _HASHEDWDFEATURES_H___

#include <shogun/lib/common.h>
#include <shogun/features/DotFeatures.h>
#include <shogun/features/StringFeatures.h>
#include <shogun/lib/Hash.h>

namespace shogun
{
template<class ST> class CStringFeatures;

/** @brief Features that compute the Weighted Degreee Kernel feature space
 * explicitly.
 *
 * \sa CWeightedDegreeStringKernel
 */
class CHashedWDFeatures: public CDotFeatures
{
public:
	/** default constructor  */
	CHashedWDFeatures();

	/** constructor
	 *
	 * @param str stringfeatures (of bytes)
	 * @param start_order do degrees starting with start_order up to order
	 * @param order of wd kernel
	 * @param from_order use first order weights from higher order weighting
	 * @param hash_bits number of bits in hash
	 */
	CHashedWDFeatures(CStringFeatures<uint8_t>* str, int32_t start_order,
			int32_t order, int32_t from_order, int32_t hash_bits=12);

	/** copy constructor */
	CHashedWDFeatures(const CHashedWDFeatures & orig);

	/** destructor */
	virtual ~CHashedWDFeatures();

	/** obtain the dimensionality of the feature space
	 *
	 * (not mix this up with the dimensionality of the input space, usually
	 * obtained via get_num_features())
	 *
	 * @return dimensionality
	 */
	virtual int32_t get_dim_feature_space() const
	{
		return w_dim;
	}

	/** compute dot product between vector1 and vector2,
	 * appointed by their indices
	 *
	 * @param vec_idx1 index of first vector
	 * @param df DotFeatures (of same kind) to compute dot product with
	 * @param vec_idx2 index of second vector
	 */
	virtual float64_t dot(int32_t vec_idx1, CDotFeatures* df, int32_t vec_idx2);

	/** compute dot product between vector1 and a dense vector
	 *
	 * @param vec_idx1 index of first vector
	 * @param vec2 pointer to real valued vector
	 * @param vec2_len length of real valued vector
	 */
	virtual float64_t dense_dot(int32_t vec_idx1, const float64_t* vec2,
			int32_t vec2_len);

	/** add vector 1 multiplied with alpha to dense vector2
	 *
	 * @param alpha scalar alpha
	 * @param vec_idx1 index of first vector
	 * @param vec2 pointer to real valued vector
	 * @param vec2_len length of real valued vector
	 * @param abs_val if true add the absolute value
	 */
	virtual void add_to_dense_vec(float64_t alpha, int32_t vec_idx1,
			float64_t* vec2, int32_t vec2_len, bool abs_val=false);

	/** get number of non-zero features in vector
	 *
	 * @param num which vector
	 * @return number of non-zero features in vector
	 */
	virtual int32_t get_nnz_features_for_vector(int32_t num);

	#ifndef DOXYGEN_SHOULD_SKIP_THIS
	/** iterator for weighted spectrum features */
	struct hashed_wd_feature_iterator
	{
		/** pointer to feature vector */
		uint16_t* vec;
		/** index of vector */
		int32_t vidx;
		/** length of vector */
		int32_t vlen;
		/** if we need to free the vector*/
		bool vfree;

		/** feature index */
		int32_t index;

	};
	#endif

	/** iterate over the non-zero features
	 *
	 * call get_feature_iterator first, followed by get_next_feature and
	 * free_feature_iterator to cleanup
	 *
	 * @param vector_index the index of the vector over whose components to
	 *			iterate over
	 * @return feature iterator (to be passed to get_next_feature)
	 */
	virtual void* get_feature_iterator(int32_t vector_index);

	/** iterate over the non-zero features
	 *
	 * call this function with the iterator returned by get_first_feature
	 * and call free_feature_iterator to cleanup
	 *
	 * @param index is returned by reference (-1 when not available)
	 * @param value is returned by reference
	 * @param iterator as returned by get_first_feature
	 * @return true if a new non-zero feature got returned
	 */
	virtual bool get_next_feature(int32_t& index, float64_t& value,
			void* iterator);

	/** clean up iterator
	 * call this function with the iterator returned by get_first_feature
	 *
	 * @param iterator as returned by get_first_feature
	 */
	virtual void free_feature_iterator(void* iterator);

	/** duplicate feature object
	 *
	 * @return feature object
	 */
	virtual CFeatures* duplicate() const;

	/** get feature type
	 *
	 * @return templated feature type
	 */
	virtual EFeatureType get_feature_type() const
	{
		return F_UNKNOWN;
	}

	/** get feature class
	 *
	 * @return feature class
	 */
	virtual EFeatureClass get_feature_class() const
	{
		return C_WD;
	}

	virtual int32_t get_num_vectors() const
	{
		return num_strings;
	}

	/** set normalization constant
	 * @param n n=0 means automagic */
	void set_normalization_const(float64_t n=0);

	/** get normalization constant */
	inline float64_t get_normalization_const()
	{
		return normalization_const;
	}

	/** @return object name */
	virtual const char* get_name() const
	{
		return "HashedWDFeatures";
	}

protected:

	/** create wd kernel weighting heuristic */
	void set_wd_weights();

protected:
	/** stringfeatures the wdfeatures are based on*/
	CStringFeatures<uint8_t>* strings;

	/** degree */
	int32_t degree;
	/** start_degree */
	int32_t start_degree;
	/** from degree */
	int32_t from_degree;
	/** length of string in vector */
	int32_t string_length;
	/** number of strings */
	int32_t num_strings;
	/** size of alphabet */
	int32_t alphabet_size;
	/** w dim */
	int32_t w_dim;
	/** partial w dim == hashsize*/
	int32_t partial_w_dim;
	/** wd weights */
	float64_t* wd_weights;
	/** mask */
	uint32_t mask;
	/** number of bits in hash */
	int32_t m_hash_bits;

	/** normalization const */
	float64_t normalization_const;
};
}
#endif // _HASHEDWDFEATURES_H___