diff --git a/src/opt/hdf5/COMMENT b/src/opt/hdf5/COMMENT
deleted file mode 100644
index 6ed9dd6..0000000
--- a/src/opt/hdf5/COMMENT
+++ /dev/null
@@ -1 +0,0 @@
-coming soon
diff --git a/src/opt/mpi/include/raindex.h b/src/opt/mpi/include/raindex.h
new file mode 100644
index 0000000..2992c0d
--- /dev/null
+++ b/src/opt/mpi/include/raindex.h
@@ -0,0 +1,208 @@
+// -*- C++ -*-
+/**
+   
+   @file opt/mpi/include/raindex.h
+   @brief RAIndex declarations.
+
+   Copyright (c) 2024 Christian Zimmermann. All rights reserved.
+   Mail: chizeta@f3l.de
+   
+**/
+
+#ifndef __cxz_mpi_raindex_h__
+#define __cxz_mpi_raindex_h__
+
+#include "cnorxz.h"
+
+namespace CNORXZ
+{
+
+    /** ****
+	Index for multi-ranked array.
+	This is meant to be a global index. For local iterations
+	a YIndex is sufficient.
+	@tparam T data type.
+     */
+    template <typename T>
+    class RAIndex : public IndexInterface<RAIndex,Tuple<SizeT,Vector<DType>>>
+    {
+    public:
+	typedef IndexInterface<RAIndex,Tuple<SizeT,Vector<DType>>> IB;
+	typedef MRange<RRange,YRange> RangeType;
+	typedef Tuple<SizeT,Vector<DType>> MetaType;
+
+	INDEX_RANDOM_ACCESS_ITERATOR_DEFS(MetaType);
+
+	/** Default constructor. */
+	RAIndex() = default;
+
+	/** Move constructor. */
+	RAIndex(RAIndex&& i) = default;
+
+	/** Move assignment. */
+	RAIndex& operator=(RAIndex&& i) = default;
+
+	/** Copy constructor.
+	    No default copy: Have to copy sub-index instances
+	 */
+	RAIndex(const RAIndex& i);
+
+	/** Copy assigment.
+	    No default copy: Have to copy sub-index instances
+	 */
+	RAIndex& operator=(const RAIndex& i);
+
+	/** Construct from sub-index pointers.
+	    @param is Vector of XIndex pointers.
+	    @param geom Rank geometry.
+	 */
+	RAIndex(const Vector<XIndexPtr>& is, const Vector<SizeT>& geom);
+
+	/** Construct from sub-index pointers, specify index format.
+	    @param bs Index format (YFormat).
+	    @param is Vector of XIndex pointers.
+	    @param geom Rank geometry.
+	 */
+	RAIndex(const YFormat& bs, const Vector<XIndexPtr>& is, const Vector<SizeT>& geom);
+
+	/** Construct from a range and an initial lexicographic position
+	    @param range Range to iterate over.
+	    @param geom Rank geometry.
+	    @param lexpos Initial lexicographic position.
+	 */
+	RAIndex(const RangePtr& range, const Vector<SizeT>& geom, SizeT lexpos = 0);
+
+	/** Construct from a range and an initial lexicographic position, specify format.
+	    @param range Range to iterate over.
+	    @param bs Index format.
+	    @param geom Rank geometry.
+	    @param lexpos Initial lexicographic position.
+	 */
+	RAIndex(const RangePtr& range, const YFormat& bs, const Vector<SizeT>& geom, SizeT lexpos = 0);
+	
+	/** @copydoc IndexInterface::operator=(SizeT) */
+	RAIndex& operator=(SizeT lexpos);
+
+	/** @copydoc IndexInterface::operator++() */
+	RAIndex& operator++();
+
+	/** @copydoc IndexInterface::operator--() */
+	RAIndex& operator--();
+
+	/** @copydoc IndexInterface::operator+() */
+	RAIndex operator+(Int n) const;
+
+	/** @copydoc IndexInterface::operator-() */
+	RAIndex operator-(Int n) const;
+
+	/** @copydoc IndexInterface::operator-(CIndex) */
+	SizeT operator-(const RAIndex& i) const;
+
+	/** @copydoc IndexInterface::operator+=() */
+	RAIndex& operator+=(Int n);
+
+	/** @copydoc IndexInterface::operator-=() */
+	RAIndex& operator-=(Int n);
+
+	/** @copydoc IndexInterface::lex() */
+	SizeT lex() const;
+
+	/** @copydoc IndexInterface::pmax() */
+	UPos pmax() const;
+
+	/** @copydoc IndexInterface::lmax() */
+	UPos lmax() const;
+
+	/** @copydoc IndexInterface::id() */
+	IndexId<0> id() const;
+	
+	const T& operator*() const;
+
+	const T* operator->() const;
+
+	/** @copydoc IndexInterface::dim() */
+	SizeT dim() const;
+
+	/** @copydoc IndexInterface::range() */
+	Sptr<YRange> range() const;
+
+	/** @copydoc IndexInterface::stepSize() */
+	UPos stepSize(const IndexId<0> id) const;
+
+	/** @copydoc IndexInterface::stringMeta() */
+	String stringMeta() const;
+
+	/** @copydoc IndexInterface::meta() */
+	Vector<DType> meta() const;
+
+	/** @copydoc IndexInterface::at() */
+	RAIndex& at(const Vector<DType>& meta);
+
+	/** @copydoc IndexInterface::prange() */
+	RangePtr prange(const RAIndex& last) const;
+
+	/** @copydoc IndexInterface::deepFormat() */
+	Vector<SizeT> deepFormat() const;
+
+	/** @copydoc IndexInterface::deepMax() */
+	Vector<SizeT> deepMax() const;
+
+	/** @copydoc IndexInterface::reformat() */
+	RAIndex& reformat(const Vector<SizeT>& f, const Vector<SizeT>& s);
+
+	/** @copydoc IndexInterface::ifor() */
+	DXpr<None> ifor(const DXpr<None>& xpr, NoF&& f) const;
+
+	/** @copydoc IndexInterface::formatIsTrivial() */
+	bool formatIsTrivial() const;
+
+	/** Replace sub-index instances.
+	    All linearized positions are updated accordingly.
+	    @param i DPack which provides the new sub-index instance 
+	 */
+	RAIndex& operator()(const DPack& i);
+
+	/** Update all linearized positions. */
+	RAIndex& operator()();
+
+	/** Get all sub-indices
+	    @return Pack of sub-indices
+	 */
+	const DPack& pack() const;
+
+	/** Get index format.
+	    @return The format.
+	 */
+	const YFormat& format() const;
+
+	/** Get lexicographic (trivial) index format.
+	    @return The lexicographic format.
+	 */
+	const YFormat& lexFormat() const;
+
+	/** Set the index format.
+	    @param bs The new format.
+	 */
+	RAIndex& setFormat(const YFormat& bs);
+
+	/** Set position of given sub index and update total index position.
+	    @param ind Sub-index number [0,dim()-1].
+	    @param lex Lexicographic position to be assigned to the index.
+	 */
+	RAIndex& setSub(SizeT ind, SizeT lex);
+
+    private:
+	Sptr<RangeType> mRange;
+	MIndex<RIndex,YIndex> mI;
+	MFormat<2> mFormat;
+	MFormat<2> mLexFormat;
+	SizeT mLex = 0;
+	UPos mPMax = 0;
+	UPos mLMax = 0;
+	const T* mLoc = nullptr;
+	Vector<T> mBuf; // used if iterating over content on different rank 
+    };
+    
+}
+
+#endif
diff --git a/src/opt/mpi/include/rarray.h b/src/opt/mpi/include/rarray.h
new file mode 100644
index 0000000..4f743bb
--- /dev/null
+++ b/src/opt/mpi/include/rarray.h
@@ -0,0 +1,50 @@
+// -*- C++ -*-
+/**
+   
+   @file opt/mpi/include/rarray.h
+   @brief RArray declarations.
+
+   Copyright (c) 2024 Christian Zimmermann. All rights reserved.
+   Mail: chizeta@f3l.de
+   
+**/
+
+#ifndef __cxz_mpi_rarray_h__
+#define __cxz_mpi_rarray_h__
+
+#include "cnorxz.h"
+
+namespace CNORXZ
+{
+    /** ****
+	Multi-dimensional multi-rank array.
+	@tparam T data type.
+     */
+    template <typename T>
+    class RArray : public ArrayBase<T>
+    {
+    public:
+	typedef CArrayBase<T> AB;
+	typedef typename RAIndex const_iterator;
+
+	using CArrayBase<T>::operator[];
+	using ArrayBase<T>::operator[];
+
+	DEFAULT_MEMBERS(RArray);
+	
+	virtual const T* data() const override;
+	virtual T* data() override;
+	virtual const_iterator cbegin() const override;
+	virtual const_iterator cend() const override;
+	virtual bool isView() const override;
+
+    protected:
+	virtual bool formatIsTrivial() const override final;
+	
+    private:
+	Vector<T> mCont;
+	RangePtr mRRange;
+    };
+}
+
+#endif