diff --git a/libsrc/core/mpi_wrapper.hpp b/libsrc/core/mpi_wrapper.hpp
index 3675db7e..ee252f23 100644
--- a/libsrc/core/mpi_wrapper.hpp
+++ b/libsrc/core/mpi_wrapper.hpp
@@ -254,6 +254,15 @@ namespace ngcore
       return global_d;
     }
 
+    template <typename T, typename T2 = decltype(GetMPIType<T>())> 
+    void AllReduce (FlatArray<T> d, const MPI_Op & op) const
+    {
+      static Timer t("MPI - AllReduce Array"); RegionTimer reg(t);
+      if (size == 1) return d;
+      
+      MPI_Allreduce (MPI_IN_PLACE, d.Data(), d.Size(), GetMPIType<T>(), op, comm);
+    }
+    
     template <typename T, typename T2 = decltype(GetMPIType<T>())> 
     void Bcast (T & s, int root = 0) const {
       if (size == 1) return ;
@@ -396,6 +405,9 @@ namespace ngcore
     template <typename T>
     T AllReduce (T d, const MPI_Op & op) const { return d; }
 
+    template <typename T>
+    void AllReduce (FlatArray<T> d, const MPI_Op & op) const { ; }
+    
     template <typename T>
     void Bcast (T & s, int root = 0) const { ; }