fix map metric

src/metric/map_metric.hpp

@@ -56,6 +56,15 @@ public:
         sum_query_weights_ += query_weights_[i];
       }
     }
+
+    npos_per_query_.resize(num_queries_, 0);
+    for (data_size_t i = 0; i < num_queries_; ++i) {
+      for (data_size_t j = query_boundaries_[i]; j < query_boundaries_[i + 1]; ++j) {
+        if (label_[j] > 0.5f) {
+          ++npos_per_query_[i];
+        }
+      }
+    }
   }
 
   const std::vector<std::string>& GetName() const override {
@@ -66,7 +75,7 @@ public:
     return 1.0f;
   }
 
-  void CalMapAtK(std::vector<int> ks, const float* label,
+  void CalMapAtK(std::vector<int> ks, data_size_t npos, const float* label,
                  const double* score, data_size_t num_data, std::vector<double>* out) const {
     // get sorted indices by score
     std::vector<data_size_t> sorted_idx;
@@ -80,7 +89,7 @@ public:
     double sum_ap = 0.0f;
     data_size_t cur_left = 0;
     for (size_t i = 0; i < ks.size(); ++i) {
-      data_size_t cur_k = ks[i];
+      data_size_t cur_k = static_cast<data_size_t>(ks[i]);
       if (cur_k > num_data) { cur_k = num_data; }
       for (data_size_t j = cur_left; j < cur_k; ++j) {
         data_size_t idx = sorted_idx[j];
@@ -89,7 +98,11 @@ public:
           sum_ap += static_cast<double>(num_hit) / (j + 1.0f);
         }
       }
-      (*out)[i] = sum_ap / cur_k;
+      if (npos > 0) {
+        (*out)[i] = sum_ap / std::min(npos, cur_k);
+      } else {
+        (*out)[i] = 1.0f;
+      }
       cur_left = cur_k;
     }
   }
@@ -104,7 +117,7 @@ public:
       #pragma omp parallel for schedule(guided) firstprivate(tmp_map)
       for (data_size_t i = 0; i < num_queries_; ++i) {
         const int tid = omp_get_thread_num();
-        CalMapAtK(eval_at_, label_ + query_boundaries_[i],
+        CalMapAtK(eval_at_, npos_per_query_[i], label_ + query_boundaries_[i],
                   score + query_boundaries_[i], query_boundaries_[i + 1] - query_boundaries_[i], &tmp_map);
         for (size_t j = 0; j < eval_at_.size(); ++j) {
           result_buffer_[tid][j] += tmp_map[j];
@@ -114,7 +127,7 @@ public:
       #pragma omp parallel for schedule(guided) firstprivate(tmp_map)
       for (data_size_t i = 0; i < num_queries_; ++i) {
         const int tid = omp_get_thread_num();
-        CalMapAtK(eval_at_, label_ + query_boundaries_[i],
+        CalMapAtK(eval_at_, npos_per_query_[i], label_ + query_boundaries_[i],
                   score + query_boundaries_[i], query_boundaries_[i + 1] - query_boundaries_[i], &tmp_map);
         for (size_t j = 0; j < eval_at_.size(); ++j) {
           result_buffer_[tid][j] += tmp_map[j] * query_weights_[i];
@@ -150,6 +163,7 @@ private:
   /*! \brief Number of threads */
   int num_threads_;
   std::vector<std::string> name_;
+  std::vector<data_size_t> npos_per_query_;
 };
 
 }  // namespace LightGBM