diff --git a/src/opt/mpi/include/mpi_base.h b/src/opt/mpi/include/mpi_base.h
new file mode 100644
index 0000000..678eddb
--- /dev/null
+++ b/src/opt/mpi/include/mpi_base.h
@@ -0,0 +1,34 @@
+// -*- C++ -*-
+
+/**
+   
+   @file
+   @brief
+
+   Copyright (c) 2024 Christian Zimmermann. All rights reserved.
+   Mail: chizeta@f3l.de
+   
+**/
+
+#ifndef __cxz_mpi_base_h__
+#define __cxz_mpi_base_h__
+
+#include "cnorxz.h"
+#include "mpi.h"
+
+namespace CNORXZ
+{
+    namespace mpi
+    {
+	// wrapper functions
+	
+	/** Get number of THIS rank. */
+	SizeT getRankNumber();
+
+	/** Get total number of ranks. */
+	SizeT getNumRanks();
+	
+    } // namespace mpi
+} // namespace CNORXZ
+
+#endif
diff --git a/src/opt/mpi/include/rrange.cc.h b/src/opt/mpi/include/rrange.cc.h
index ed23b87..d928457 100644
--- a/src/opt/mpi/include/rrange.cc.h
+++ b/src/opt/mpi/include/rrange.cc.h
@@ -2,7 +2,7 @@
 /**
    
    @file opt/mpi/include/rrange.cc.h
-   @brief RRange and RIndex declaration.
+   @brief RRange and RIndex template implementation.
    
    Copyright (c) 2024 Christian Zimmermann. All rights reserved.
    Mail: chizeta@f3l.de
@@ -424,40 +424,6 @@ namespace CNORXZ
 	    mLocal(loc),
 	    mGeom(geom)
 	{}
-
-	/*===========================+
-	 |    non-member functions   |
-	 +===========================*/
-
-	template <class RangeJ, class RangeK>
-	RangePtr rrange(const Sptr<RangeJ>& global, const Sptr<RangeK>& geom)
-	{
-	    if constexpr(has_static_sub<typename RangeJ::IndexType>::value and
-			 has_static_sub<typename RangeK::IndexType>::value) {
-		static_assert(typename RangeI::NR == typename RangeK::NR,
-			      "ranges have to be of same dimension");
-
-		constexpr SizeT N = typename RangeI::NR;
-		auto mr = ifor<0,N>( [&](auto mu) {
-		    return split( global->space()[CSizeT<mu>{}], geom->space()[CSizeT<mu>{}] );
-		}, [](const auto&... r) { return xplMrange(r,...); } );
-		typedef std::remove_reference<decltype(*mr)>::type RangeI;
-		return RRangeFactory<RangeI,RangeK>(mr, geom).create(); // explicit range type!!!
-	    }
-	    // other cases!!!
-	    else {
-		CXZ_ASSERT(global->dim() == geom->dim(),
-			   "ranges have to be of same dimension, got "
-			   << global->dim() << " and " << geom->dim());
-		Vector<RangePtr> o(global->dim());
-		for(SizeT mu = 0; mu != global->dim(); ++mu){
-		    o[mu] = split( global->space()[mu], geom->space()[mu] );
-		}
-		const Sptr<YRange> yr = xplYrange(o);
-		return RRangeFactory<YRange,RangeK>(yr, geom).create();
-	    }
-	}
-	
 	
     } // namespace mpi
 } // namespace CNORXZ
diff --git a/src/opt/mpi/include/rrange.h b/src/opt/mpi/include/rrange.h
index cab6b30..80a9a53 100644
--- a/src/opt/mpi/include/rrange.h
+++ b/src/opt/mpi/include/rrange.h
@@ -243,8 +243,7 @@ namespace CNORXZ
 	    @param global Global range.
 	    @param geom Rank geometry.
 	*/
-	template <class RangeJ, class RangeK>
-	RangePtr rrange(const Sptr<RangeJ>& global, const Sptr<RangeK>& geom);
+	RangePtr rrange(const RangePtr& global, const RangePtr& geom);
 	
     } // namespace mpi
 } // namespace CNORXZ
diff --git a/src/opt/mpi/lib/mpi_base.cc b/src/opt/mpi/lib/mpi_base.cc
new file mode 100644
index 0000000..fda42c0
--- /dev/null
+++ b/src/opt/mpi/lib/mpi_base.cc
@@ -0,0 +1,38 @@
+// -*- C++ -*-
+
+/**
+   
+   @file
+   @brief
+
+   Copyright (c) 2024 Christian Zimmermann. All rights reserved.
+   Mail: chizeta@f3l.de
+   
+**/
+
+#include "mpi_base.h"
+
+namespace CNORXZ
+{
+    namespace mpi
+    {
+
+	SizeT getRankNumber()
+	{
+	    int s;
+	    const int ret = MPI_Comm_rank(MPI_COMM_WORLD, &s);
+	    CXZ_ASSERT(ret == MPI_SUCCESS, "got mpi error = " << ret);
+	    return static_cast<SizeT>(s);
+	}
+
+	SizeT getNumRanks()
+	{
+	    int s;
+	    const int ret = MPI_Comm_size(MPI_COMM_WORLD, &s);
+	    CXZ_ASSERT(ret == MPI_SUCCESS, "got mpi error = " << ret);
+	    return static_cast<SizeT>(s);
+	}
+	
+    } // namespace mpi
+} // namespace CNORXZ
+
diff --git a/src/opt/mpi/lib/rrange.cc b/src/opt/mpi/lib/rrange.cc
new file mode 100644
index 0000000..ff93029
--- /dev/null
+++ b/src/opt/mpi/lib/rrange.cc
@@ -0,0 +1,74 @@
+// -*- C++ -*-
+/**
+   
+   @file opt/mpi/lib/rrange.h
+   @brief RRange and RIndex implementation.
+   
+   Copyright (c) 2024 Christian Zimmermann. All rights reserved.
+   Mail: chizeta@f3l.de
+   
+**/
+
+#include "rrange.h"
+
+namespace CNORXZ
+{
+    namespace mpi
+    {
+
+	/*===========================+
+	 |    non-member functions   |
+	 +===========================*/
+
+	MArray<RangePtr> rsplit(const RangePtr& global, const RangePtr& geom)
+	{
+	    if(geom->dim() > 1){
+		CXZ_ASSERT(global->dim() == geom->dim(),
+			   "global range has to be of same dimension as geometry range, got "
+			   << global->dim() << " and " << geom->dim());
+		MArray<RangePtr> o(geom);
+		YIndex k = geom->begin();
+		YIndex ke = geom->end();
+		auto mu = std::make_shared<CIndex>(geom->sub());
+		MArray<MArray<RangePtr>> rs(geom->sub()->range());
+		rs(mu) = operation( [&](const SizeT i) { return rsplit(globla->sub(i), geom->sub(i)); } , xpr(mu) );
+		Vector elem(geom->sub()->range());
+		for(; k != ke; ++k){
+		    mu->ifor( operation( [&](const SizeT i){ elem[i] = rs[i][k->pack()[i]]; }, xpr(mu) ) )();
+		    o[k] = YRangeFactory(elem).create();
+		}
+		return o;
+	    }
+	    else {
+		CXZ_ASSERT(global->size() % geom->size() == 0,
+			   "global range has to be dividible by geometry range, got "
+			   << global->size() << " and " << k->lmax().val());
+		const SizeT n = global->size() / geom->size();
+		auto k = std::make_shared<CIndex>(geom);
+		auto jb = global->begin();
+		auto je = global->begin();
+		MArray<RangePtr> o(geom);
+		o(k) = operation( [&](const SizeT x){ jb = n*x; je = n*(x+1)-1; return jb.prange(je) } , xpr(k) );
+		return o;
+	    }
+	}
+	
+	RangePtr rrange(const RangePtr& global, const RangePtr& geom)
+	{
+	    const MArray<RangePtr> rs = rsplit(global, geom);
+	    RangePtr o = nullptr;
+	    for(auto ri = rs.begin(); ri != rs.end(); ++ri){
+		if(ri->lex() == getRangeNum()){
+		    o = *ri;
+		}
+	    }
+	    assert(o);
+	    auto loc = rangeCast<YRange>(global);
+	    auto geo = rangeCast<YRange>(geom);
+	    return RRangeFactory<YRange,YRange>(loc, geom).create();
+	}
+	
+	
+    } // namespace mpi
+} // namespace CNORXZ
+