LazyDensityOperator.h

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// Copyright András Vukics 2006–2014. Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE.txt)
// -*- C++ -*-
#ifndef CPPQEDCORE_QUANTUMDATA_LAZYDENSITYOPERATOR_H_INCLUDED
#define CPPQEDCORE_QUANTUMDATA_LAZYDENSITYOPERATOR_H_INCLUDED

#include "LazyDensityOperatorFwd.h"

#include "DimensionsBookkeeper.h"

#include "BlitzArray.h"
#include "ComplexExtensions.h"

#include <boost/shared_ptr.hpp>

#include <boost/mpl/if.hpp>


namespace mpl=boost::mpl;



namespace quantumdata {



template<typename V, typename T, int RANK, typename F>
const T
partialTrace(const LazyDensityOperator<RANK>&, F function);



template<int RANK> 
class LazyDensityOperator 
  : public DimensionsBookkeeper<RANK,true>
{
public:
  typedef boost::shared_ptr<const LazyDensityOperator> Ptr; 
  
  typedef DimensionsBookkeeper<RANK,true> Base;

  typedef typename Base::Dimensions Dimensions; 

  typedef IdxTiny<RANK> Idx; 

  virtual ~LazyDensityOperator() {}

private:
  class IndexerProxy
  {
  public:
    IndexerProxy(const LazyDensityOperator* ldo, const Idx& firstIndex) : ldo_(ldo), firstIndex_(firstIndex) {}

    const dcomp operator()(const Idx& secondIndex) const {return ldo_->index(firstIndex_,secondIndex);}

    template<typename... SubscriptPack>
    const dcomp operator()(int s0, SubscriptPack... subscriptPack) const
    {
      static_assert( mpl::size<mpl::vector<SubscriptPack...> >::value==RANK-1 , "Incorrect number of subscripts for LazyDensityOperator::IndexerProxy." );
      return operator()(Idx(s0,subscriptPack...));
    }

    operator double() const {return real(ldo_->index(firstIndex_,firstIndex_));}

  private:
    const LazyDensityOperator*const ldo_;
    const Idx firstIndex_;

  };

  friend class IndexerProxy;

public:
  const IndexerProxy operator()(const Idx& firstIndex) const {return IndexerProxy(this,firstIndex);}


  template<typename... SubscriptPack>
  const IndexerProxy operator()(int s0, SubscriptPack... subscriptPack) const
  {
    static_assert( mpl::size<mpl::vector<SubscriptPack...> >::value==RANK-1 , "Incorrect number of subscripts for LazyDensityOperator." );
    return operator()(Idx(s0,subscriptPack...));
  }

  double trace() const {return trace_v();} 
  


  template<typename V>
  const ldo::DiagonalIterator<RANK,V> begin() const; 

  template<typename V>
  const ldo::DiagonalIterator<RANK,V> end  () const; 

  
protected:
  LazyDensityOperator(const Dimensions& dims) : Base(dims) {}

private:
  virtual const dcomp index(const Idx& i, const Idx& j) const = 0;
  
  virtual double trace_v() const = 0;

};



template<int RANK>
const DArray<1> deflate(const LazyDensityOperator<RANK>&, bool offDiagonals);


} // quantumdata

#endif // CPPQEDCORE_QUANTUMDATA_LAZYDENSITYOPERATOR_H_INCLUDED