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This commit is contained in:
tqchen 2014-08-17 20:47:20 -07:00
parent 5a472145de
commit 4ed4b08146
4 changed files with 45 additions and 36 deletions
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39
src/learner/objective-inl.hpp
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@ -8,6 +8,7 @@
#include <vector>
#include <cmath>
#include <algorithm>
#include <utility>
#include <functional>
#include "../data.h"
#include "./objective.h"
@ -254,7 +255,6 @@ class LambdaRankObj : public IObjFunction {
utils::Check(gptr.size() != 0 && gptr.back() == preds.size(),
"group structure not consistent with #rows");
const unsigned ngroup = static_cast<unsigned>(gptr.size() - 1);
#pragma omp parallel
{
// parall construct, declare random number generator here, so that each
@ -263,7 +263,6 @@ class LambdaRankObj : public IObjFunction {
std::vector<LambdaPair> pairs;
std::vector<ListEntry> lst;
std::vector< std::pair<float, unsigned> > rec;
#pragma omp for schedule(static)
for (unsigned k = 0; k < ngroup; ++k) {
lst.clear(); pairs.clear();
@ -402,7 +401,6 @@ class LambdaRankObjNDCG : public LambdaRankObj {
std::sort(labels.begin(), labels.end(), std::greater<float>());
IDCG = CalcDCG(labels);
}
if (IDCG == 0.0) {
for (size_t i = 0; i < pairs.size(); ++i) {
pairs[i].weight = 0.0f;
@ -416,8 +414,10 @@ class LambdaRankObjNDCG : public LambdaRankObj {
float neg_loginv = 1.0f / logf(neg_idx + 2.0f);
int pos_label = static_cast<int>(sorted_list[pos_idx].label);
int neg_label = static_cast<int>(sorted_list[neg_idx].label);
float original = ((1<<pos_label)-1) * pos_loginv + ((1<<neg_label)-1) * neg_loginv;
float changed = ((1<<neg_label)-1) * pos_loginv + ((1<<pos_label)-1) * neg_loginv;
float original =
((1 << pos_label) - 1) * pos_loginv + ((1 << neg_label) - 1) * neg_loginv;
float changed =
((1 << neg_label) - 1) * pos_loginv + ((1 << pos_label) - 1) * neg_loginv;
float delta = (original - changed) * IDCG;
if (delta < 0.0f) delta = - delta;
pairs[i].weight = delta;
@ -442,11 +442,17 @@ class LambdaRankObjMAP : public LambdaRankObj {
protected:
struct MAPStats {
/* \brief the accumulated precision */
/*! \brief the accumulated precision */
float ap_acc;
/* \brief the accumulated precision assuming a positive instance is missing */
/*!
* \brief the accumulated precision,
* assuming a positive instance is missing
*/
float ap_acc_miss;
/* \brief the accumulated precision assuming that one more positive instance is inserted ahead*/
/*!
* \brief the accumulated precision,
* assuming that one more positive instance is inserted ahead
*/
float ap_acc_add;
/* \brief the accumulated positive instance count */
float hits;
@ -454,7 +460,7 @@ class LambdaRankObjMAP : public LambdaRankObj {
MAPStats(float ap_acc, float ap_acc_miss, float ap_acc_add, float hits)
: ap_acc(ap_acc), ap_acc_miss(ap_acc_miss), ap_acc_add(ap_acc_add), hits(hits) {}
};
/*
/*!
* \brief Obtain the delta MAP if trying to switch the positions of instances in index1 or index2
* in sorted triples
* \param sorted_list the list containing entry information
@ -463,7 +469,8 @@ class LambdaRankObjMAP : public LambdaRankObj {
*/
inline float GetLambdaMAP(const std::vector<ListEntry> &sorted_list,
int index1, int index2,
std::vector<MAPStats> &map_stats){
std::vector<MAPStats> *p_map_stats) {
std::vector<MAPStats> &map_stats = *p_map_stats;
if (index1 == index2 || map_stats[map_stats.size() - 1].hits == 0) {
return 0.0f;
}
@ -482,7 +489,6 @@ class LambdaRankObjMAP : public LambdaRankObj {
changed += map_stats[index2 - 1].ap_acc_miss - map_stats[index1].ap_acc_miss;
changed += map_stats[index2].hits / (index2 + 1);
}
float ans = (changed - original) / (map_stats[map_stats.size() - 1].hits);
if (ans < 0) ans = -ans;
return ans;
@ -493,7 +499,8 @@ class LambdaRankObjMAP : public LambdaRankObj {
* \param map_stats a vector containing the accumulated precisions for each position in a list
*/
inline void GetMAPStats(const std::vector<ListEntry> &sorted_list,
std::vector<MAPStats> &map_acc){
std::vector<MAPStats> *p_map_acc) {
std::vector<MAPStats> &map_acc = *p_map_acc;
map_acc.resize(sorted_list.size());
float hit = 0, acc1 = 0, acc2 = 0, acc3 = 0;
for (size_t i = 1; i <= sorted_list.size(); ++i) {
@ -506,13 +513,15 @@ class LambdaRankObjMAP : public LambdaRankObj {
map_acc[i - 1] = MAPStats(acc1, acc2, acc3, hit);
}
}
virtual void GetLambdaWeight(const std::vector<ListEntry> &sorted_list, std::vector<LambdaPair> *io_pairs) {
virtual void GetLambdaWeight(const std::vector<ListEntry> &sorted_list,
std::vector<LambdaPair> *io_pairs) {
std::vector<LambdaPair> &pairs = *io_pairs;
std::vector<MAPStats> map_stats;
GetMAPStats(sorted_list, map_stats);
GetMAPStats(sorted_list, &map_stats);
for (size_t i = 0; i < pairs.size(); ++i) {
pairs[i].weight =
GetLambdaMAP(sorted_list, pairs[i].pos_index, pairs[i].neg_index, map_stats);
GetLambdaMAP(sorted_list, pairs[i].pos_index,
pairs[i].neg_index, &map_stats);
}
}
};