fixup! [RF] Improve hash-assisted find in RooAbsCollection.

Author: hageboeck

roofit/roofitcore/inc/RooAbsCollection.h

@@ -54,6 +54,12 @@ ROOT::RRangeCast<T, true, Range_t> dynamic_range_cast(Range_t &&coll)
 
 class RooCmdArg;
 
+namespace RooFit {
+namespace Detail {
+struct HashAssistedFind;
+}
+}
+
 class RooAbsCollection : public TObject, public RooPrintable {
 public:
   using Storage_t = std::vector<RooAbsArg*>;
@@ -381,7 +387,7 @@ class RooAbsCollection : public TObject, public RooPrintable {
 private:
   std::unique_ptr<LegacyIterator_t> makeLegacyIterator (bool forward = true) const;
 
-  struct HashAssistedFind;
+  using HashAssistedFind = RooFit::Detail::HashAssistedFind;
   mutable std::unique_ptr<HashAssistedFind> _hashAssistedFind; //!
   std::size_t _sizeThresholdForMapSearch; //!
 

roofit/roofitcore/src/RooAbsCollection.cxx

@@ -62,6 +62,9 @@ char* operator+( streampos&, char* );
 
 ClassImp(RooAbsCollection);
 
+namespace RooFit {
+namespace Detail {
+
 /**
  * Helper for hash-map-assisted finding of elements by name.
  * Create this helper if finding of elements by name is needed.
@@ -71,7 +74,7 @@ ClassImp(RooAbsCollection);
  * gets renamed, this counter will be increased, and the name to
  * object map becomes invalid. In this case, it has to be recreated.
  */
-struct RooAbsCollection::HashAssistedFind {
+struct HashAssistedFind {
 
   /// Inititalise empty hash map for fast finding by name.
   template<typename It_t>
@@ -114,7 +117,8 @@ struct RooAbsCollection::HashAssistedFind {
   std::size_t rooNameRegCounterWhereMapWasValid = 0;
 };
 
-
+}
+}
 
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -1561,8 +1565,8 @@ void RooAbsCollection::insert(RooAbsArg* item) {
 ////////////////////////////////////////////////////////////////////////////////
 /// \param[in] flag Switch hash map on or off.
 void RooAbsCollection::useHashMapForFind(bool flag) const {
+  if (flag && !_hashAssistedFind) _hashAssistedFind = std::make_unique<HashAssistedFind>(_list.begin(), _list.end());
   if (!flag) _hashAssistedFind = nullptr;
-  else _hashAssistedFind = std::make_unique<HashAssistedFind>(_list.begin(), _list.end());
 }