fixed some typo and added some documentation

src/storm/settings/modules/JitBuilderSettings.cpp

@@ -34,8 +34,8 @@ namespace storm {
                                 .addArgument(storm::settings::ArgumentBuilder::createStringArgument("dir", "The directory containing the carl headers.").build()).build());
                 this->addOption(storm::settings::OptionBuilder(moduleName, compilerFlagsOptionName, false, "The flags passed to the compiler.")
                                 .addArgument(storm::settings::ArgumentBuilder::createStringArgument("flags", "The compiler flags.").build()).build());
-                this->addOption(storm::settings::OptionBuilder(moduleName, optimizationLevelOptionName, false, "The optimization level to use.")
-                                .addArgument(storm::settings::ArgumentBuilder::createUnsignedIntegerArgument("level", "The compiler flags.").setDefaultValueUnsignedInteger(3).build()).build());
+                this->addOption(storm::settings::OptionBuilder(moduleName, optimizationLevelOptionName, false, "Sets the optimization level.")
+                                .addArgument(storm::settings::ArgumentBuilder::createUnsignedIntegerArgument("level", "The level to use.").setDefaultValueUnsignedInteger(3).build()).build());
             }
             
             bool JitBuilderSettings::isCompilerSet() const {

src/storm/storage/dd/cudd/InternalCuddDdManager.cpp

@@ -85,7 +85,9 @@ namespace storm {
                 }
             }
             
-            // Connect the two variables so they are not 'torn apart' during dynamic reordering.
+            // Connect the variables so they are not 'torn apart' by dynamic reordering.
+            // Note that MTR_FIXED preserves the order of the layers. While this is not always necessary to preserve,
+            // (for example) the hybrid engine relies on this connection, so we choose MTR_FIXED instead of MTR_DEFAULT.
             cuddManager.MakeTreeNode(result.front().getIndex(), numberOfLayers, MTR_FIXED);
             
             // Keep track of the number of variables.