Don't use cached items in multi-threaded mode for now until we have proper immutability

src/ifcgeom/Iterator.h

@@ -171,6 +171,10 @@ namespace IfcGeom {
 
 			converter_ = new ifcopenshell::geometry::Converter(geometry_library_, ifc_file, settings_);
 			std::vector<ifcopenshell::geometry::geometry_conversion_task> reps;
+			if (num_threads_ != 1) {
+				// @todo this shouldn't be necessary with properly immutable taxonomy items
+				converter_->mapping()->use_caching() = false;
+			}
 			converter_->mapping()->get_representations(reps, filters_);
 
 			for (auto& task : reps) {

src/ifcgeom/abstract_mapping.h

@@ -28,6 +28,8 @@ namespace geometry {
     class abstract_mapping {
 	protected:
 		Settings settings_;
+
+		bool use_caching_ = true;
 	public:
 		abstract_mapping(Settings& s) : settings_(s) {}
 
@@ -45,6 +47,9 @@ namespace geometry {
 
 		const Settings& settings() const { return settings_; }
 		Settings& settings() { return settings_; }
+
+		bool use_caching() const { return use_caching_; }
+		bool& use_caching() { return use_caching_; }
     };
 
 	namespace impl {

src/ifcgeom/mapping/mapping.cpp

@@ -520,9 +520,11 @@ taxonomy::ptr mapping::map_impl(const IfcSchema::IfcStyledItem* inst) {
 
 taxonomy::ptr mapping::map(const IfcBaseInterface* inst) {
 	auto iden = inst->as<IfcUtil::IfcBaseClass>()->identity();
-	auto it = cache_.find(iden);
-	if (it != cache_.end()) {
-		return it->second;
+	if (use_caching_) {
+		auto it = cache_.find(iden);
+		if (it != cache_.end()) {
+			return it->second;
+		}
 	}
 	taxonomy::ptr item = nullptr;
 
@@ -532,7 +534,7 @@ taxonomy::ptr mapping::map(const IfcBaseInterface* inst) {
 
 #include "bind_convert_impl.i"
 
-	if (item) {
+	if (use_caching_ && item) {
 		cache_.insert({ iden, item });
 	}
 	else {