From fdba6e9c46dd348ce1a372e35c123df22b57959c Mon Sep 17 00:00:00 2001
From: tqchen <tianqi.tchen@gmail.com>
Date: Tue, 19 Aug 2014 08:02:29 -0700
Subject: [PATCH] add pratio

---
 src/learner/evaluation-inl.hpp | 35 ++++++++++++++++++++++++++++++++++
 src/learner/evaluation.h       |  1 +
 2 files changed, 36 insertions(+)

diff --git a/src/learner/evaluation-inl.hpp b/src/learner/evaluation-inl.hpp
index 43fe48726..17a0d5589 100644
--- a/src/learner/evaluation-inl.hpp
+++ b/src/learner/evaluation-inl.hpp
@@ -155,6 +155,41 @@ struct EvalAMS : public IEvaluator {
   float ratio_;
 };
 
+/*! \brief precision with cut off at top percentile */
+struct EvalPrecisionRatio : public IEvaluator{
+ public:
+  EvalPrecisionRatio( const char *name ) : name_(name) {
+    utils::Assert(sscanf( name, "apratio@%f", &ratio_) == 1, "BUG");
+  }
+  virtual float Eval(const std::vector<float> &preds,
+                     const MetaInfo &info) const {
+    utils::Assert(preds.size() == info.labels.size(), "label size predict size not match");
+    std::vector< std::pair<float, unsigned> > rec;
+    for (size_t j = 0; j < preds.size(); ++j) {
+      rec.push_back(std::make_pair(preds[j], j));
+    }
+    std::sort(rec.begin(), rec.end(), CmpFirst);
+    double pratio = CalcPRatio( rec, info );
+    return static_cast<float>(pratio);
+  }
+  virtual const char *Name(void) const{
+    return name_.c_str();
+  }
+ protected:
+  inline double CalcPRatio(const std::vector< std::pair<float,unsigned> >& rec, const MetaInfo &info) const{
+    size_t cutoff = static_cast<size_t>(ratio_ * rec.size());
+    double wt_hit = 0.0, wsum = 0.0;
+    for (size_t j = 0; j < cutoff; ++j) {
+      wt_hit += info.labels[rec[j].second];
+      wsum += wt_hit / j;
+     }
+    return wsum / cutoff;
+  }
+ protected:
+  float ratio_;
+  std::string name_;
+};
+
 /*! \brief Area under curve, for both classification and rank */
 struct EvalAuc : public IEvaluator {
   virtual float Eval(const std::vector<float> &preds,
diff --git a/src/learner/evaluation.h b/src/learner/evaluation.h
index fa25aa7d7..79ad4902e 100644
--- a/src/learner/evaluation.h
+++ b/src/learner/evaluation.h
@@ -41,6 +41,7 @@ inline IEvaluator* CreateEvaluator(const char *name) {
   if (!strcmp(name, "auc")) return new EvalAuc();
   if (!strncmp(name, "ams@", 4)) return new EvalAMS(name);
   if (!strncmp(name, "pre@", 4)) return new EvalPrecision(name);
+  if (!strncmp(name, "pratio@", 4)) return new EvalPrecisionRatio(name);
   if (!strncmp(name, "map", 3)) return new EvalMAP(name);
   if (!strncmp(name, "ndcg", 3)) return new EvalNDCG(name);
   utils::Error("unknown evaluation metric type: %s", name);