diff --git a/libsrc/core/paje_trace.cpp b/libsrc/core/paje_trace.cpp
index 9b4ac053..1a1c9303 100644
--- a/libsrc/core/paje_trace.cpp
+++ b/libsrc/core/paje_trace.cpp
@@ -942,7 +942,7 @@ namespace ngcore
     size_t imax_mem_allocated = 0;
 
     const auto & names = MemoryTracer::GetNames();
-    const auto & tree = MemoryTracer::GetTree();
+    const auto & parents = MemoryTracer::GetParents();
     size_t N = names.size();
 
     Array<size_t> mem_allocated_id;
@@ -1006,39 +1006,27 @@ namespace ngcore
     Array<TreeNode*> nodes;
     nodes.SetSize(N);
     nodes = nullptr;
+    Array<Array<int>> children(N);
+
     Array<size_t> sorting; // topological sorting (parents before children)
     sorting.SetAllocSize(N);
-    ArrayMem<size_t, 100> stack;
-
-    // find root nodes in memory tracer tree, i.e. they have no parents
-    Array<int> parents;
-    parents.SetSize(N);
-    parents = -1;
-    for( const auto & [iparent, children] : tree )
-      for (auto child_id : children)
-      {
-        if(parents[child_id] != -1)
-          std::cerr << "Error in memory tracer: multiple parents found for " << names[child_id] << std::endl;
-        parents[child_id] = iparent;
-      }
 
     for(auto i : IntRange(1, N))
-      if(parents[i]==-1)
-      {
-        sorting.Append(i);
-        if(tree.count(i))
-          stack.Append(i);
-      }
+        children[parents[i]].Append(i);
+
+    ArrayMem<size_t, 100> stack;
+    sorting.Append(0);
+    stack.Append(0);
 
     while(stack.Size())
     {
       auto current = stack.Last();
       stack.DeleteLast();
 
-      for(const auto child : tree.at(current))
+      for(const auto child : children[current])
       {
         sorting.Append(child);
-        if(tree.count(child))
+        if(children[child].Size())
           stack.Append(child);
       }
     }
diff --git a/libsrc/core/profiler.cpp b/libsrc/core/profiler.cpp
index 66365321..33ef98f4 100644
--- a/libsrc/core/profiler.cpp
+++ b/libsrc/core/profiler.cpp
@@ -114,8 +114,8 @@ namespace ngcore
   NgProfiler prof; // NOLINT
 
 #ifdef NETGEN_TRACE_MEMORY
-  std::vector<std::string> MemoryTracer::names{"root"};
-  std::map< int, std::vector<int> > MemoryTracer::tree;
+  std::vector<std::string> MemoryTracer::names{"all"};
+  std::vector<int> MemoryTracer::parents{-1};
 #endif // NETGEN_TRACE_MEMORY
 
 } // namespace ngcore
diff --git a/libsrc/core/profiler.hpp b/libsrc/core/profiler.hpp
index cdd945bd..208b7a4e 100644
--- a/libsrc/core/profiler.hpp
+++ b/libsrc/core/profiler.hpp
@@ -324,12 +324,13 @@ namespace ngcore
   {
     #ifdef NETGEN_TRACE_MEMORY
     NGCORE_API static std::vector<std::string> names;
-    NGCORE_API static std::map< int, std::vector<int> > tree;
+    NGCORE_API static std::vector<int> parents;
 
     static int CreateId(const std::string& name)
     {
       int id = names.size();
       names.push_back(name);
+      parents.push_back(0);
       if(id==10*NgProfiler::SIZE)
         std::cerr << "Allocated " << id << " MemoryTracer objects" << std::endl;
       return id;
@@ -400,7 +401,7 @@ namespace ngcore
     void Track( T & obj, const std::string& name ) const
     {
       obj.GetMemoryTracer().Activate(obj, name);
-      tree[id].push_back(obj.GetMemoryTracer().GetId());
+      parents[obj.GetMemoryTracer().GetId()] = id;
     }
 
     static std::string GetName(int id)
@@ -433,7 +434,7 @@ namespace ngcore
 
 
     static const std::vector<std::string> & GetNames() { return names; }
-    static const std::map<int, std::vector<int>> & GetTree() { return tree; }
+    static const std::vector<int> & GetParents() { return parents; }
 #else // NETGEN_TRACE_MEMORY
   public:
     MemoryTracer() {}