Extended critical section and added docu for CoW

elsa/core/CMakeLists.txt

@@ -30,6 +30,12 @@ set(MODULE_SOURCES
 add_library(${ELSA_MODULE_TARGET_NAME} ${MODULE_HEADERS} ${MODULE_SOURCES})
 add_library(elsa::${ELSA_MODULE_NAME} ALIAS ${ELSA_MODULE_TARGET_NAME})
 
+# use OpenMP is available
+find_package(OpenMP REQUIRED)
+if(OpenMP_CXX_FOUND)
+    target_link_libraries(${ELSA_MODULE_TARGET_NAME} PRIVATE OpenMP::OpenMP_CXX)
+endif()
+
 target_include_directories(${ELSA_MODULE_TARGET_NAME}
         PUBLIC
         $<INSTALL_INTERFACE:include/${ELSA_MODULE_NAME}>

elsa/core/DataContainer.cpp

@@ -283,10 +283,12 @@ namespace elsa {
     template <typename data_t>
     void DataContainer<data_t>::detach()
     {
-        if (_dataHandler.use_count() == 1)
-            return;
-
-        _dataHandler = _dataHandler->clone();
+        if (_dataHandler.use_count() != 1) {
+#pragma omp barrier
+#pragma omp single
+            _dataHandler = _dataHandler->clone();
+        }
+        return;
     }
 
     // ------------------------------------------

elsa/core/DataContainer.h

@@ -23,6 +23,9 @@ namespace elsa
      * This class provides a container for a signal that is stored in memory. This signal can
      * be n-dimensional, and will be stored in memory in a linearized fashion. The information
      * on how this linearization is performed is provided by an associated DataDescriptor.
+     *
+     * The class implements copy-on-write. Therefore any non-const functions should call the
+     * detach() function first to trigger the copy-on-write mechanism.
      */
     template <typename data_t = real_t>
     class DataContainer {
@@ -88,7 +91,6 @@ namespace elsa
          */
         DataContainer<data_t>& operator=(DataContainer<data_t>&& other);
 
-
         /// return the current DataDescriptor
         const DataDescriptor& getDataDescriptor() const;
 
@@ -191,8 +193,6 @@ namespace elsa
         /// comparison with another DataContainer
         bool operator!=(const DataContainer<data_t>& other) const;
 
-        /// creates the deep copy for the copy-on-write mechanism
-        void detach();
     private:
         /// the current DataDescriptor
         std::unique_ptr<DataDescriptor> _dataDescriptor;
@@ -205,6 +205,9 @@ namespace elsa
 
         /// private constructor accepting a DataDescriptor and a DataHandler
         explicit DataContainer(const DataDescriptor& dataDescriptor, std::unique_ptr<DataHandler<data_t>> dataHandler);
+
+        /// creates the deep copy for the copy-on-write mechanism
+        void detach();
     };
 
 

elsa/core/tests/test_DataContainer.cpp

@@ -402,8 +402,7 @@ SCENARIO("Testing the copy-on-write mechanism") {
             dc.dot(dc2);
             dc.l1Norm();
 
-            // TODO(Jens): this can't really be tested as the member is private - make test scenario friend?
-            THEN("the data handlers are the same") {
+            THEN("the data should still be the same") {
                 REQUIRE(dc3 == dc);
             }
         }

elsa/projectors/BinaryMethod.cpp

@@ -64,8 +64,6 @@ namespace elsa
     template <bool adjoint>
     void BinaryMethod<data_t>::traverseVolume(const DataContainer<data_t>& vector, DataContainer<data_t>& result) const
     {
-        result.detach();
-
         index_t maxIterations{0};
         if (adjoint) {
             maxIterations = vector.getSize();

elsa/projectors/JosephsMethod.cpp

@@ -65,7 +65,6 @@ namespace elsa
     template <bool adjoint>
     void JosephsMethod<data_t>::traverseVolume(const DataContainer<data_t>& vector, DataContainer<data_t>& result) const
     {
-        result.detach();
         if(adjoint) result = 0;
 
         const index_t sizeOfRange = _rangeDescriptor->getNumberOfCoefficients();