add functions to be used by the json library to create json objects.

The necessary to_json(...) function are used. One can create a json
object by e.g. "nlohmann::json ttjson = nlohmann::json(tt)" with tt
being a timing tree

src/core/timing/Timer.h

@@ -27,6 +27,7 @@
 #include "CpuPolicy.h"
 #include "WcPolicy.h"
 #include "core/DataTypes.h"
+#include "core/extern/json.hpp"
 
 #include <limits>
 
@@ -441,6 +442,22 @@ inline void Timer<TP>::merge( const Timer<TP> & other )
 }
 //**********************************************************************************************************************
 
+//**********************************************************************************************************************
+/*!\brief Converts timer to json The signature is required by the json library
+// \relates Timer
+*/
+template < typename TP > // Timing policy
+void to_json( nlohmann::json& j, const Timer< TP >& timer )
+{
+   j = nlohmann::json{{"total", timer.total()},
+                      {"average", timer.average()},
+                      {"count", timer.getCounter()},
+                      {"min", timer.min()},
+                      {"max", timer.max()},
+                      {"variance", timer.variance()}};
+}
+//**********************************************************************************************************************
+
 } // namespace timing
 
 typedef timing::Timer<timing::CpuPolicy>  CpuTimer;

src/core/timing/TimingNode.h

@@ -30,6 +30,8 @@
 #include "core/mpi/MPIManager.h"
 #include "core/mpi/Reduce.h"
 #include "core/mpi/SetReduction.h"
+#include "core/extern/json.hpp"
+
 
 #include <algorithm>
 #include <iomanip>
@@ -481,6 +483,43 @@ std::ostream& operator<<(std::ostream& os, const TimingNode<TP>& tn)
    return os;
 }
 
+/// convertes a TimingNode to json. The signature is required by the json library
+/// \relates TimingNode
+template < typename TP > // Timing policy
+void to_json( nlohmann::json& j, const TimingNode< TP >& tn )
+{
+   /// ignore the first timer in the timing node since it is empty
+   if( tn.last_ == nullptr )
+   {
+      j = nlohmann::json( tn.tree_ );
+   } else
+   {
+      j           = nlohmann::json( tn.timer_ );
+      j["childs"] = nlohmann::json( tn.tree_ );
+   }
+}
+
+namespace internal {
+/// adds a sub timer containing the remainder of all other subtimers on the same hierarchy level
+/// \relates TimingNode
+template< typename TP >
+// Timing policy
+void addRemainderNodes(timing::TimingNode<TP> &tn) {
+   if (tn.tree_.empty()) {
+      return;
+   }
+   double remainder = tn.timer_.total();
+   for (auto i = tn.tree_.begin(); i != tn.tree_.end(); ++i) {
+      remainder -= i->second.timer_.total();
+      addRemainderNodes(i->second);
+   }
+   if (tn.last_ != nullptr) {
+      WALBERLA_ASSERT( tn.tree_.find("Remainder") == tn.tree_.end());
+      tn.tree_["Remainder"].timer_ = timing::Timer<TP>(1, 0, 0, remainder, 0);
+      tn.tree_["Remainder"].last_ = &tn;
+   }
+}
+} /// namespace internal
 }
 
 typedef timing::TimingNode<timing::WcPolicy>  WcTimingNode;

src/core/timing/TimingTree.h

@@ -28,6 +28,7 @@
 #include "core/logging/Logging.h"
 #include "core/mpi/MPIManager.h"
 #include "core/mpi/Reduce.h"
+#include "core/extern/json.hpp"
 
 #include <algorithm>
 #include <iostream>
@@ -88,6 +89,10 @@ public:
    /// Returns the name of the currently running timer
    /// Might be expensive due to value search.
    std::string getCurrentTimerName() const;
+
+   /// Returns a copy of the timing tree containing the remaining time as a subnode
+   TimingTree< TP > getCopyWithRemainder() const;
+
 private:
    /// Tree data structure
    TimingNode<TP>  root_;
@@ -239,6 +244,21 @@ std::string TimingTree<TP>::getCurrentTimerName() const
    return "No timer found!";
 }
 
+template < typename TP > // Timing policy
+TimingTree< TP > TimingTree< TP >::getCopyWithRemainder() const
+{
+   TimingTree< TP > tt( *this );
+   timing::internal::addRemainderNodes< TP >( tt.root_ );
+   return tt;
+}
+
+/// convertes a TimingTree to json. The signature is required by the json library
+/// \relates TimingTree
+template < typename TP > // Timing policy
+void to_json( nlohmann::json& j, const TimingTree< TP >& tt )
+{
+   j = nlohmann::json( tt.getRawData() );
+}
 }
 
 typedef timing::TimingTree<timing::WcPolicy>  WcTimingTree;