Fix the O(N^2) bug of passColName and passRowName

ERGO-Code · May 30, 2024 · eeb92c0 · eeb92c0
1 parent 4f54ef2
commit eeb92c0
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Showing 3 changed files with 21 additions and 7 deletions.
diff --git a/src/lp_data/HStruct.h b/src/lp_data/HStruct.h
@@ -117,6 +117,8 @@ struct HighsNameHash {
   std::unordered_map<std::string, int> name2index;
   void form(const std::vector<std::string>& name);
   bool hasDuplicate(const std::vector<std::string>& name);
+  void update(int index, const std::string& old_name,
+              const std::string& new_name);
   void clear();
 };
 

diff --git a/src/lp_data/Highs.cpp b/src/lp_data/Highs.cpp
@@ -591,8 +591,8 @@ HighsStatus Highs::passColName(const HighsInt col, const std::string& name) {
     return HighsStatus::kError;
   }
   this->model_.lp_.col_names_.resize(num_col);
+  this->model_.lp_.col_hash_.update(col, this->model_.lp_.col_names_[col], name);
   this->model_.lp_.col_names_[col] = name;
-  this->model_.lp_.col_hash_.clear();
   return HighsStatus::kOk;
 }
 
@@ -611,8 +611,8 @@ HighsStatus Highs::passRowName(const HighsInt row, const std::string& name) {
     return HighsStatus::kError;
   }
   this->model_.lp_.row_names_.resize(num_row);
+  this->model_.lp_.row_hash_.update(row, this->model_.lp_.row_names_[row], name);
   this->model_.lp_.row_names_[row] = name;
-  this->model_.lp_.row_hash_.clear();
   return HighsStatus::kOk;
 }
 

diff --git a/src/lp_data/HighsLp.cpp b/src/lp_data/HighsLp.cpp
@@ -594,14 +594,13 @@ void HighsNameHash::form(const std::vector<std::string>& name) {
   size_t num_name = name.size();
   this->clear();
   for (size_t index = 0; index < num_name; index++) {
-    const bool duplicate = !this->name2index.emplace(name[index], index).second;
+    auto emplace_result = this->name2index.emplace(name[index], index);
+    const bool duplicate = !emplace_result.second;
     if (duplicate) {
       // Find the original and mark it as duplicate
-      auto search = this->name2index.find(name[index]);
-      assert(search != this->name2index.end());
+      auto& search = emplace_result.first;
       assert(int(search->second) < int(this->name2index.size()));
-      this->name2index.erase(search);
-      this->name2index.insert({name[index], kHashIsDuplicate});
+      search->second = kHashIsDuplicate;
     }
   }
 }
@@ -618,4 +617,17 @@ bool HighsNameHash::hasDuplicate(const std::vector<std::string>& name) {
   return has_duplicate;
 }
 
+void HighsNameHash::update(int index, const std::string& old_name,
+                           const std::string& new_name) {
+  this->name2index.erase(old_name);
+  auto emplace_result = this->name2index.emplace(new_name, index);
+  const bool duplicate = !emplace_result.second;
+  if (duplicate) {
+    // Find the original and mark it as duplicate
+    auto& search = emplace_result.first;
+    assert(int(search->second) < int(this->name2index.size()));
+    search->second = kHashIsDuplicate;
+  }
+}
+
 void HighsNameHash::clear() { this->name2index.clear(); }