refine predictor logic in c_api

src/c_api.cpp

@@ -154,7 +154,7 @@ public:
     boosting_->RollbackOneIter();
   }
 
-  void PrepareForPrediction(int num_iteration, int predict_type) {
+  Predictor NewPredictor(int num_iteration, int predict_type) {
     std::lock_guard<std::mutex> lock(mutex_);
     boosting_->SetNumIterationForPred(num_iteration);
     bool is_predict_leaf = false;
@@ -166,22 +166,15 @@ public:
     } else {
       is_raw_score = false;
     }
-    predictor_.reset(new Predictor(boosting_.get(), is_raw_score, is_predict_leaf));
+    // not threading safe now
+    // boosting_->SetNumIterationForPred may be set by other thread during prediction. 
+    return Predictor(boosting_.get(), is_raw_score, is_predict_leaf);
   }
 
   void GetPredictAt(int data_idx, score_t* out_result, int64_t* out_len) {
     boosting_->GetPredictAt(data_idx, out_result, out_len);
   }
 
-  std::vector<double> Predict(const std::vector<std::pair<int, double>>& features) {
-    return predictor_->GetPredictFunction()(features);
-  }
-
-  void PredictForFile(const char* data_filename, const char* result_filename, bool data_has_header) {
-    std::lock_guard<std::mutex> lock(mutex_);
-    predictor_->Predict(data_filename, result_filename, data_has_header);
-  }
-
   void SaveModelToFile(int num_iteration, const char* filename) {
     boosting_->SaveModelToFile(num_iteration, filename);
   }
@@ -232,8 +225,6 @@ private:
   std::vector<std::vector<std::unique_ptr<Metric>>> valid_metrics_;
   /*! \brief Training objective function */
   std::unique_ptr<ObjectiveFunction> objective_fun_;
-  /*! \brief Using predictor for prediction task */
-  std::unique_ptr<Predictor> predictor_;
   /*! \brief mutex for threading safe call */
   std::mutex mutex_;
 };
@@ -692,9 +683,9 @@ DllExport int LGBM_BoosterPredictForFile(BoosterHandle handle,
   const char* result_filename) {
   API_BEGIN();
   Booster* ref_booster = reinterpret_cast<Booster*>(handle);
-  ref_booster->PrepareForPrediction(static_cast<int>(num_iteration), predict_type);
+  auto predictor = ref_booster->NewPredictor(static_cast<int>(num_iteration), predict_type);
   bool bool_data_has_header = data_has_header > 0 ? true : false;
-  ref_booster->PredictForFile(data_filename, result_filename, bool_data_has_header);
+  predictor.Predict(data_filename, result_filename, bool_data_has_header);
   API_END();
 }
 
@@ -713,8 +704,7 @@ DllExport int LGBM_BoosterPredictForCSR(BoosterHandle handle,
   float* out_result) {
   API_BEGIN();
   Booster* ref_booster = reinterpret_cast<Booster*>(handle);
-  ref_booster->PrepareForPrediction(static_cast<int>(num_iteration), predict_type);
-
+  auto predictor = ref_booster->NewPredictor(static_cast<int>(num_iteration), predict_type);
   auto get_row_fun = RowFunctionFromCSR(indptr, indptr_type, indices, data, data_type, nindptr, nelem);
   int num_preb_in_one_row = ref_booster->GetBoosting()->NumberOfClasses();
   if (predict_type == C_API_PREDICT_LEAF_INDEX) {
@@ -728,7 +718,7 @@ DllExport int LGBM_BoosterPredictForCSR(BoosterHandle handle,
 #pragma omp parallel for schedule(guided)
   for (int i = 0; i < nrow; ++i) {
     auto one_row = get_row_fun(i);
-    auto predicton_result = ref_booster->Predict(one_row);
+    auto predicton_result = predictor.GetPredictFunction()(one_row);
     for (int j = 0; j < static_cast<int>(predicton_result.size()); ++j) {
       out_result[i * num_preb_in_one_row + j] = static_cast<float>(predicton_result[j]);
     }
@@ -749,8 +739,7 @@ DllExport int LGBM_BoosterPredictForMat(BoosterHandle handle,
   float* out_result) {
   API_BEGIN();
   Booster* ref_booster = reinterpret_cast<Booster*>(handle);
-  ref_booster->PrepareForPrediction(static_cast<int>(num_iteration), predict_type);
-
+  auto predictor = ref_booster->NewPredictor(static_cast<int>(num_iteration), predict_type);
   auto get_row_fun = RowPairFunctionFromDenseMatric(data, nrow, ncol, data_type, is_row_major);
   int num_preb_in_one_row = ref_booster->GetBoosting()->NumberOfClasses();
   if (predict_type == C_API_PREDICT_LEAF_INDEX) {
@@ -763,7 +752,7 @@ DllExport int LGBM_BoosterPredictForMat(BoosterHandle handle,
 #pragma omp parallel for schedule(guided)
   for (int i = 0; i < nrow; ++i) {
     auto one_row = get_row_fun(i);
-    auto predicton_result = ref_booster->Predict(one_row);
+    auto predicton_result = predictor.GetPredictFunction()(one_row);
     for (int j = 0; j < static_cast<int>(predicton_result.size()); ++j) {
       out_result[i * num_preb_in_one_row + j] = static_cast<float>(predicton_result[j]);
     }