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Merge branch 'dev' of https://github.com/tqchen/xgboost into dev

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kalenhaha 2014-05-12 22:22:32 +08:00
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regrank/xgboost_regrank_sample.h
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#ifndef _XGBOOST_REGRANK_SAMPLE_H_
#define _XGBOOST_REGRANK_SAMPLE_H_
#include <vector>
#include"../utils/xgboost_utils.h"
namespace xgboost {
namespace regrank {
namespace sample {
/*
* \brief the data structure to maintain the sample pairs
* similar to the adjacency list of a graph
*/
struct Pairs {
/*
* \brief constructor given the start and end offset of the sampling group
* in overall instances
* \param start the begin index of the group
* \param end the end index of the group
*/
Pairs(int start, int end) :start_(start), end_(end){
for (int i = start; i < end; i++){
std::vector<int> v;
pairs_.push_back(v);
}
}
/*
* \brief retrieve the related pair information of an data instances
* \param index, the index of retrieved instance
* \return the index of instances paired
*/
std::vector<int> GetPairs(int index) const{
utils::Assert(index >= start_ && index < end_, "The query index out of sampling bound");
return pairs_[index - start_];
}
/*
* \brief add in a sampled pair
* \param index the index of the instance to sample a friend
* \param paired_index the index of the instance sampled as a friend
*/
void push(int index, int paired_index){
pairs_[index - start_].push_back(paired_index);
}
std::vector< std::vector<int> > pairs_;
int start_;
int end_;
};
/*
* \brief the interface of pair sampler
*/
struct IPairSampler {
/*
* \brief Generate sample pairs given the predcions, labels, the start and the end index
* of a specified group
* \param preds, the predictions of all data instances
* \param labels, the labels of all data instances
* \param start, the start index of a specified group
* \param end, the end index of a specified group
* \return the generated pairs
*/
virtual std::vector< std::pair<int, int> > GenPairs(const std::vector<float> &preds,
const std::vector<float> &labels,
int start, int end) = 0;
};
enum{
BINARY_LINEAR_SAMPLER
};
/*! \brief A simple pair sampler when the rank relevence scale is binary
* for each positive instance, we will pick a negative
* instance and add in a pair. When using binary linear sampler,
* we should guarantee the labels are 0 or 1
*/
struct BinaryLinearSampler :public IPairSampler{
virtual std::vector< std::pair<int, int> > GenPairs(const std::vector<float> &preds,
const std::vector<float> &labels,
int start, int end) {
std::vector< std::pair<int, int> > ans;
return ans;
}
};
/*! \brief Pair Sampler Wrapper*/
struct PairSamplerWrapper{
public:
inline void AssignSampler(int sampler_index){
switch (sampler_index){
case BINARY_LINEAR_SAMPLER:sampler_ = &binary_linear_sampler; break;
default:utils::Error("Cannot find the specified sampler");
}
}
~PairSamplerWrapper(){ delete sampler_; }
std::vector< std::pair<int, int> > GenPairs(const std::vector<float> &preds,
const std::vector<float> &labels,
int start, int end){
utils::Assert(sampler_ != NULL, "Not config the sampler yet. Add rank:sampler in the config file\n");
return sampler_->GenPairs(preds, labels, start, end);
}
private:
BinaryLinearSampler binary_linear_sampler;
IPairSampler *sampler_;
};
}
}
}
#endif