simplify the logic of load model from string

include/LightGBM/utils/common.h

@@ -81,14 +81,14 @@ inline static std::vector<std::string> Split(const char* c_str, const char* deli
   return ret;
 }
 
-template<typename T>
-inline std::string Join(const std::vector<T>& data, char delimiters) {
-  std::stringstream result_stream_buf;
-  result_stream_buf << data[0];
-  for (size_t i = 1; i < data.size(); ++i) {
-    result_stream_buf << delimiters << data[i];
+inline static std::string FindFromLines(const std::vector<std::string>& lines, const char* key_word) {
+  for (auto& line : lines) {
+    size_t find_pos = line.find(key_word);
+    if (find_pos != std::string::npos) {
+      return line;
+    }
   }
-  return result_stream_buf.str();
+  return "";
 }
 
 inline static const char* Atoi(const char* p, int* out) {
@@ -310,7 +310,8 @@ inline static std::vector<int> StringToIntArray(const std::string& str, char del
   return ret;
 }
 
-inline static std::string Join(const std::vector<std::string>& strs, char delimiter) {
+template<typename T>
+inline static std::string Join(const std::vector<T>& strs, char delimiter) {
   if (strs.size() <= 0) {
     return std::string("");
   }
@@ -323,7 +324,8 @@ inline static std::string Join(const std::vector<std::string>& strs, char delimi
   return ss.str();
 }
 
-inline static std::string Join(const std::vector<std::string>& strs, size_t start, size_t end, char delimiter) {
+template<typename T>
+inline static std::string Join(const std::vector<T>& strs, size_t start, size_t end, char delimiter) {
   if (end - start <= 0) {
     return std::string("");
   }

src/boosting/gbdt.cpp

@@ -403,79 +403,40 @@ void GBDT::LoadModelFromString(const std::string& model_str) {
   // use serialized string to restore this object
   models_.clear();
   std::vector<std::string> lines = Common::Split(model_str.c_str(), '\n');
-  size_t i = 0;
 
   // get number of classes
-  while (i < lines.size()) {
-    size_t find_pos = lines[i].find("num_class=");
-    if (find_pos != std::string::npos) {
-      std::vector<std::string> strs = Common::Split(lines[i].c_str(), '=');
-      Common::Atoi(strs[1].c_str(), &num_class_);
-      ++i;
-      break;
+  auto line = Common::FindFromLines(lines, "num_class=");
+  if (line.size() > 0) {
+    Common::Atoi(Common::Split(line.c_str(), '=')[1].c_str(), &num_class_);
   } else {
-      ++i;
-    }
-  }
-  if (i == lines.size()) {
     Log::Fatal("Model file doesn't specify the number of classes");
     return;
   }
-
   // get index of label
-  i = 0;
-  while (i < lines.size()) {
-    size_t find_pos = lines[i].find("label_index=");
-    if (find_pos != std::string::npos) {
-      std::vector<std::string> strs = Common::Split(lines[i].c_str(), '=');
-      Common::Atoi(strs[1].c_str(), &label_idx_);
-      ++i;
-      break;
+  line = Common::FindFromLines(lines, "label_index=");
+  if (line.size() > 0) {
+    Common::Atoi(Common::Split(line.c_str(), '=')[1].c_str(), &label_idx_);
   } else {
-      ++i;
-    }
-  }
-  if (i == lines.size()) {
     Log::Fatal("Model file doesn't specify the label index");
     return;
   }
-
   // get max_feature_idx first
-  i = 0;
-  while (i < lines.size()) {
-    size_t find_pos = lines[i].find("max_feature_idx=");
-    if (find_pos != std::string::npos) {
-      std::vector<std::string> strs = Common::Split(lines[i].c_str(), '=');
-      Common::Atoi(strs[1].c_str(), &max_feature_idx_);
-      ++i;
-      break;
+  line = Common::FindFromLines(lines, "max_feature_idx=");
+  if (line.size() > 0) {
+    Common::Atoi(Common::Split(line.c_str(), '=')[1].c_str(), &max_feature_idx_);
   } else {
-      ++i;
-    }
-  }
-  if (i == lines.size()) {
     Log::Fatal("Model file doesn't specify max_feature_idx");
     return;
   }
   // get sigmoid parameter
-  i = 0;
-  while (i < lines.size()) {
-    size_t find_pos = lines[i].find("sigmoid=");
-    if (find_pos != std::string::npos) {
-      std::vector<std::string> strs = Common::Split(lines[i].c_str(), '=');
-      Common::Atof(strs[1].c_str(), &sigmoid_);
-      ++i;
-      break;
+  line = Common::FindFromLines(lines, "sigmoid=");
+  if (line.size() > 0) {
+    Common::Atof(Common::Split(line.c_str(), '=')[1].c_str(), &sigmoid_);
   } else {
-      ++i;
-    }
-  }
-  // if sigmoid doesn't exists
-  if (i == lines.size()) {
     sigmoid_ = -1.0f;
   }
   // get tree models
-  i = 0;
+  size_t i = 0;
   while (i < lines.size()) {
     size_t find_pos = lines[i].find("Tree=");
     if (find_pos != std::string::npos) {
@@ -483,7 +444,7 @@ void GBDT::LoadModelFromString(const std::string& model_str) {
       int start = static_cast<int>(i);
       while (i < lines.size() && lines[i].find("Tree=") == std::string::npos) { ++i; }
       int end = static_cast<int>(i);
-      std::string tree_str = Common::Join(lines, start, end, '\n');
+      std::string tree_str = Common::Join<std::string>(lines, start, end, '\n');
       models_.push_back(new Tree(tree_str));
     } else {
       ++i;