/*
Copyright (c) 2014-2017-2018-2019, UT-Battelle, LLC
All rights reserved

[DMRG++, Version 5.]
[by G.A., Oak Ridge National Laboratory]

UT Battelle Open Source Software License 11242008

OPEN SOURCE LICENSE

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contributor to this software hereby grants, free of
charge, to any person obtaining a copy of this software
and associated documentation files (the "Software"), a
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Department of Energy nor the names of the Software
contributors may be used to endorse or promote products
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with the redistribution, with or without modification,
must include the following acknowledgment:

"This product includes software produced by UT-Battelle,
LLC under Contract No. DE-AC05-00OR22725  with the
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*********************************************************
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THE SOFTWARE IS SUPPLIED BY THE COPYRIGHT HOLDERS AND
CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED
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*/
#ifndef APPLY_OP_EXPRESSION_H
#define APPLY_OP_EXPRESSION_H

#include "ProgressIndicator.h"
#include "ApplyOperatorLocal.h"
#include "TimeVectorsKrylov.h"
#include "TimeVectorsChebyshev.h"
#include "TimeVectorsRungeKutta.h"
#include "TimeVectorsSuzukiTrotter.h"
#include "Io/IoSelector.h"
#include "TargetParamsBase.h"
#include "StageEnum.h"
#include "MultiSiteExpressionHelper.h"
#include "CorrelationsSkeleton.h"

namespace Dmrg {

template<typename TargetHelperType,
         typename VectorWithOffsetType,
         typename LanczosSolverType>
class ApplyOperatorExpression {

public:

	typedef typename TargetHelperType::RealType RealType;
	typedef typename TargetHelperType::ModelType ModelType;
	typedef typename ModelType::ParametersType ParametersType;
	typedef typename ParametersType::OptionsType OptionsType;
	typedef TargetParamsBase<ModelType> TargetParamsType;
	typedef typename TargetHelperType::LeftRightSuperType LeftRightSuperType;
	typedef typename LeftRightSuperType::BasisWithOperatorsType BasisWithOperatorsType;
	typedef typename BasisWithOperatorsType::SparseMatrixType SparseMatrixType;
	typedef typename SparseMatrixType::value_type ComplexOrRealType;
	typedef typename TargetHelperType::WaveFunctionTransfType WaveFunctionTransfType;
	typedef TimeVectorsBase<TargetParamsType,ModelType,WaveFunctionTransfType,
	LanczosSolverType,VectorWithOffsetType> TimeVectorsBaseType;
	typedef TimeVectorsKrylov<TargetParamsType,ModelType,WaveFunctionTransfType,
	LanczosSolverType,VectorWithOffsetType> TimeVectorsKrylovType;
	typedef TimeVectorsChebyshev<TargetParamsType,ModelType,WaveFunctionTransfType,
	LanczosSolverType,VectorWithOffsetType> TimeVectorsChebyshevType;
	typedef TimeVectorsRungeKutta<TargetParamsType,ModelType,WaveFunctionTransfType,
	LanczosSolverType,VectorWithOffsetType> TimeVectorsRungeKuttaType;
	typedef TimeVectorsSuzukiTrotter<TargetParamsType,ModelType,WaveFunctionTransfType,
	LanczosSolverType,VectorWithOffsetType> TimeVectorsSuzukiTrotterType;
	typedef typename ModelType::InputValidatorType InputValidatorType;
	typedef typename PsimagLite::Vector<VectorWithOffsetType>::Type VectorVectorWithOffsetType;
	typedef typename PsimagLite::Vector<SizeType>::Type VectorSizeType;
	typedef typename PsimagLite::Vector<RealType>::Type VectorRealType;
	typedef ApplyOperatorLocal<LeftRightSuperType,VectorWithOffsetType> ApplyOperatorType;
	typedef typename ApplyOperatorType::BorderEnum BorderEnumType;
	typedef typename TimeVectorsBaseType::PairType PairType;
	typedef StageEnum StageEnumType;
	typedef typename PsimagLite::Vector<StageEnum>::Type VectorStageEnumType;
	typedef MultiSiteExpressionHelper<LeftRightSuperType, VectorWithOffsetType>
	MultiSiteExpressionHelperType;
	typedef typename MultiSiteExpressionHelperType::DmrgSerializerType DmrgSerializerType;
	typedef CorrelationsSkeleton<MultiSiteExpressionHelperType, ModelType> CorrelationsSkeletonType;
	typedef typename TimeVectorsBaseType::WftHelperType WftHelperType;
	typedef typename VectorWithOffsetType::VectorType VectorType;
	typedef typename PsimagLite::Vector<typename
	PsimagLite::Vector<VectorWithOffsetType*>::Type>::Type VectorVectorVectorWithOffsetType;

	ApplyOperatorExpression(const TargetHelperType& targetHelper,
	                        SizeType indexNoAdvance)
	    : progress_("ApplyOperatorExpression"),
	      targetHelper_(targetHelper),
	      E0_(0.0),
	      time_(0.0),
	      currentTimeStep_(0),
	      indexNoAdvance_(indexNoAdvance),
	      applyOpLocal_(targetHelper.lrs(), targetHelper.withLegacyBugs()),
	      targetVectors_(0),
	      timeVectorsBase_(0),
	      wftHelper_(targetHelper.model(), targetHelper.lrs(), targetHelper.wft()),
	      multiSiteExprHelper_(targetHelper_.model().superGeometry().numberOfSites() - 2),
	      correlationsSkel_(multiSiteExprHelper_, targetHelper.model(), false)
	{
		timesWithoutAdvancement_ = 0;
		firstSeeLeftCorner_ = false;
	}

	~ApplyOperatorExpression()
	{
		delete timeVectorsBase_;
		timeVectorsBase_ = 0;
		clearPsi();
	}

	virtual void initPsi(SizeType nsectors, SizeType nexcited)
	{
		if (psi_.size() > 0) {
			bool flag = true;

			if (psi_.size() != nsectors) {
				flag = false;
			} else {
				for (SizeType i = 0; i < nsectors; ++i)
					if (psi_[i].size() != nexcited)
						flag = false;
			}

			if (flag) return;

			std::cerr<<"AOE::initPsi(): WARNING sectors/nexcited changed during run\n";
			std::cout<<"AOE::initPsi(): WARNING sectors/nexcited changed during run\n";
			clearPsi();
		}

		psi_.resize(nsectors);

		for (SizeType i = 0; i < nsectors; ++i)
			psi_[i].resize(nexcited, nullptr);
	}

	void postCtor(SizeType tstSites)
	{
		if (stage_.size() != 0)
			throw PsimagLite::RuntimeError("ApplyOperatorExpression: Internal Error\n");

		stage_.resize((tstSites == 0) ? 1 : tstSites, StageEnum::DISABLED);
	}

	SizeType getPhi(VectorWithOffsetType* phiNew,
	                RealType Eg,
	                ProgramGlobals::DirectionEnum direction,
	                SizeType site,
	                SizeType loopNumber,
	                const TargetParamsType& tstStruct)
	{
		SizeType count = 0;
		const SizeType nsectors = psi_.size();
		const SizeType sectorIndex = tstStruct.sectorIndex();
		if (sectorIndex >= nsectors)
			err("getPhi: sectors=" + ttos(nsectors) + " <= " + ttos(sectorIndex) + "\n");

		const SizeType nlevels = psi_[sectorIndex].size();
		const SizeType levelIndex = tstStruct.levelIndex();
		if (levelIndex >= nlevels)
			err("getPhi: levels=" + ttos(nlevels) + " <= " + ttos(levelIndex) + "\n");

		// deep copy needed
		VectorWithOffsetType phiOld = *(psi_[sectorIndex][levelIndex]);
		VectorWithOffsetType vectorSum;

		SizeType max = tstStruct.sites();
		if (noStageIs(StageEnum::DISABLED)) {
			max = 1;
			for (SizeType i=0;i<stage_.size();i++) {
				if (stage_[i] == StageEnum::OPERATOR)
					stage_[i] = StageEnum::WFT_NOADVANCE;
				if (stage_[i] == StageEnum::WFT_ADVANCE)
					stage_[i] = StageEnum::WFT_NOADVANCE;
			}
		}

		// Loop over each operator that needs to be applied
		// in turn to the g.s.
		for (SizeType i = 0; i < max; ++i) {

			SizeType count2 = evolve(i, Eg, direction, site, loopNumber, max - 1, tstStruct);

			if (count2 == 0) continue;

			// phi = A|psi>
			if (phiNew)
				computePhi(i, site, *phiNew, phiOld, direction, tstStruct);

			count += count2;

			if (!phiNew) continue;

			if (tstStruct.concatenation() == TargetParamsType::ConcatEnum::PRODUCT) {
				phiOld = *phiNew;
			} else {
				if (stage_[i] == StageEnum::OPERATOR) vectorSum += *phiNew;
				else vectorSum = *phiNew;
			}
		}

		if (phiNew && tstStruct.concatenation() == TargetParamsType::ConcatEnum::SUM)
			*phiNew = vectorSum;

		if (allStages(StageEnum::DISABLED)) E0_ = Eg;

		if (noStageIs(StageEnum::DISABLED)) {
			PsimagLite::OstringStream msgg(std::cout.precision());
			PsimagLite::OstringStream::OstringStreamType& msg = msgg();
			msg<<"EnergyForExp was ";
			if (tstStruct.isEnergyForExp()) {
				E0_ = tstStruct.energyForExp();
				msg<<"provided explicitly, ";
			} else {
				msg<<"not provided explicitly, ";
			}

			msg<<" value= "<<E0_;
			progress_.printline(msgg, std::cout);
		}

		return count;
	}

	bool allStages(StageEnum x) const
	{
		for (SizeType i=0;i<stage_.size();i++)
			if (stage_[i] != x) return false;
		return true;
	}

	bool noStageIs(StageEnum x) const
	{
		for (SizeType i=0;i<stage_.size();i++)
			if (stage_[i] == x) return false;
		return true;
	}

	const VectorStageEnumType& stages() const { return stage_; }

	void setStage(SizeType ind, StageEnum x)
	{
		assert(ind < stage_.size());
		stage_[ind] = x;
	}

	const RealType& energy() const
	{
		return E0_;
	}

	const ApplyOperatorType& applyOpLocal() const
	{
		return applyOpLocal_;
	}

	const VectorVectorVectorWithOffsetType& psiConst() const
	{
		return psi_;
	}

	void setOnlyOnePsi(const VectorWithOffsetType& v)
	{
		std::cerr<<"Setting only one psi\n";
		std::cout<<"Setting only one psi\n";

		clearPsi();

		psi_.resize(1);
		psi_[0].resize(1);
		psi_[0][0] = new VectorWithOffsetType(v);
	}

	template<typename SomeBasisType>
	void setPsi(SizeType sectorIndex,
	            SizeType excitedIndex,
	            VectorType& v,
	            const SomeBasisType& basis,
	            const VectorSizeType& sectors)
	{
		if (psi_.size() == 0) {
			psi_.resize(sectors.size());
			const SizeType nexcited = targetHelper_.model().params().numberOfExcited;
			for (SizeType i = 0; i < psi_.size(); ++i)
				psi_[i].resize(nexcited);
		}

		assert(sectorIndex < sectors.size());
		const SizeType sector = sectors[sectorIndex];

		assert(sectorIndex < psi_.size());
		assert(excitedIndex < psi_[sectorIndex].size());

		if (!psi_[sectorIndex][excitedIndex])
			psi_[sectorIndex][excitedIndex] = new VectorWithOffsetType;
		psi_[sectorIndex][excitedIndex]->set(v, sector, basis);
	}

	void writePsi(PsimagLite::IoSelector::Out& io, PsimagLite::String prefix) const
	{
		const SizeType nsectors = psi_.size();
		io.createGroup(prefix + "/PSI");
		io.write(nsectors, prefix + "/PSI/Size");
		for (SizeType sectorIndex = 0; sectorIndex < nsectors; ++sectorIndex) {
			const SizeType nexcited = psi_[sectorIndex].size();
			PsimagLite::String label = prefix + "/PSI/" + ttos(sectorIndex);
			io.createGroup(label);
			io.write(nexcited, label + "/Size");
			for (SizeType excitedIndex = 0; excitedIndex < nexcited; ++excitedIndex)
				psi_[sectorIndex][excitedIndex]->write(io, label + "/" + ttos(excitedIndex));
		}
	}

	void readPsi(PsimagLite::IoSelector::In& io, PsimagLite::String prefix)
	{
		clearPsi();
		SizeType nsectors = 0;
		try {
			io.read(nsectors, prefix + "/PSI/Size");
		} catch (...) {
			psi_.resize(1);
			psi_[0].resize(1);
			psi_[0][0] = new VectorWithOffsetType;
			psi_[0][0]->read(io, prefix + "PSI");
			return;
		}

		psi_.resize(nsectors);

		for (SizeType sectorIndex = 0; sectorIndex < nsectors; ++sectorIndex) {
			PsimagLite::String label = prefix + "/PSI/" + ttos(sectorIndex) + "/";
			SizeType nexcited = 0;
			io.read(nexcited, label + "Size");
			psi_[sectorIndex].resize(nexcited);
			for (SizeType excitedIndex = 0; excitedIndex < nexcited; ++excitedIndex) {
				psi_[sectorIndex][excitedIndex] = new VectorWithOffsetType;
				psi_[sectorIndex][excitedIndex]->read(io, label + ttos(excitedIndex));
			}
		}
	}

	const VectorVectorWithOffsetType& targetVectors() const
	{
		return targetVectors_;
	}

	VectorWithOffsetType& targetVectors(SizeType i) // <--- FIXME
	{
		assert(i < targetVectors_.size());
		return targetVectors_[i];
	}

	const VectorWithOffsetType& targetVectors(SizeType i) const
	{
		assert(i < targetVectors_.size());
		return targetVectors_[i];
	}

	SizeType createPvector(const VectorWithOffsetType& v)
	{
		const SizeType n = targetVectors_.size();
		targetVectors_.push_back(v);
		return n;
	}

	void destroyPvector(SizeType ind)
	{
		if (ind >= targetVectors_.size())
			err("AOE: destroyPvector\n");

		targetVectors_[ind].clear();
	}

	void trimVectors()
	{
		const SizeType n = targetVectors_.size();
		SizeType x = 0;
		for (SizeType ii = 0; ii < n; ++ii) {
			const SizeType i = n - ii - 1;
			if (targetVectors_[i].size() == 0) {
				++x;
			} else {
				break;
			}
		}

		if (x == 0) return;
		targetVectorsResize(n - x);
	}

	void targetVectorsResize(SizeType x)
	{
		if (x == 0) targetVectors_.clear();
		else targetVectors_.resize(x);

		PsimagLite::OstringStream msgg(std::cout.precision());
		PsimagLite::OstringStream::OstringStreamType& msg = msgg();
		msg<<"Number of target vectors is now "<<targetVectors_.size();
		progress_.printline(msgg, std::cout);
	}

	void initTimeVectors(const TargetParamsType& tstStruct,
	                     const VectorRealType& times,
	                     InputValidatorType& ioIn)
	{
		const LeftRightSuperType& lrs = targetHelper_.lrs();
		const ModelType& model = targetHelper_.model();
		const WaveFunctionTransfType& wft = targetHelper_.wft();

		PsimagLite::String s (__FILE__);
		s += " Unknown algorithm\n";

		switch (tstStruct.algorithm()) {
		case TargetParamsType::AlgorithmEnum::KRYLOV:
			timeVectorsBase_ = new TimeVectorsKrylovType(currentTimeStep_,
			                                             tstStruct,
			                                             times,
			                                             targetVectors_,
			                                             model,
			                                             wft,
			                                             lrs,
			                                             ioIn);
			break;
		case TargetParamsType::AlgorithmEnum::CHEBYSHEV:
			timeVectorsBase_ = new TimeVectorsChebyshevType(currentTimeStep_,
			                                                tstStruct,
			                                                times,
			                                                targetVectors_,
			                                                model,
			                                                wft,
			                                                lrs,
			                                                ioIn);
			break;
		case TargetParamsType::AlgorithmEnum::RUNGE_KUTTA:
			timeVectorsBase_ = new TimeVectorsRungeKuttaType(currentTimeStep_,
			                                                 tstStruct,
			                                                 times,
			                                                 targetVectors_,
			                                                 model,
			                                                 wft,
			                                                 lrs);
			break;
		case TargetParamsType::AlgorithmEnum::SUZUKI_TROTTER:
			timeVectorsBase_ = new TimeVectorsSuzukiTrotterType(currentTimeStep_,
			                                                    tstStruct,
			                                                    times,
			                                                    targetVectors_,
			                                                    model,
			                                                    wft,
			                                                    lrs);
			break;
		default:
			throw PsimagLite::RuntimeError(s.c_str());
		}
	}

	RealType time() const
	{
		return time_;
	}

	SizeType currentTimeStep() const { return currentTimeStep_; }

	void setCurrentTimeStep(SizeType t)
	{
		currentTimeStep_ = t;
	}

	void setCurrentTime(RealType t)
	{
		time_ = t;
	}

	void loadEnergy(PsimagLite::IoSelector::In& io,
	                PsimagLite::String label)
	{
		SizeType nsectors = 0;
		io.read(nsectors, label + "/Size");
		if (nsectors == 0)
			err("FATAL: " + label + "/Size=0");

		SizeType nexcited = 0;
		try {
			io.read(nexcited, label + "/0/Size");
		} catch (...) {
			loadEnergyLegacy(io, label);
			return;
		}

		if (nexcited == 0)
			err("FATAL: " + label + "/0/Size=0");

		io.read(E0_, label + "/0/0");
	}

	void multiplyTimeVector(SizeType i,RealType factor)
	{
		targetVectors_[i] = factor*targetVectors_[i];
	}

	void calcTimeVectors(const PsimagLite::Vector<SizeType>::Type& indices,
	                     RealType Eg,
	                     const VectorWithOffsetType& phi,
	                     ProgramGlobals::DirectionEnum direction,
	                     bool allOperatorsApplied,
	                     bool wftAndAdvanceIfNeeded,
	                     const PsimagLite::Vector<SizeType>::Type& block,
	                     bool isLastCall)
	{
		typename TimeVectorsBaseType::ExtraData extra(direction,
		                                              allOperatorsApplied,
		                                              wftAndAdvanceIfNeeded,
		                                              block,
		                                              isLastCall,
		                                              time_);
		timeVectorsBase_->calcTimeVectors(indices,
		                                  Eg,
		                                  phi,
		                                  extra);
	}

	void applyOneOperator(SizeType loopNumber,
	                      SizeType indexOfOperator,
	                      SizeType site,
	                      VectorWithOffsetType& phiNew,
	                      const VectorWithOffsetType& psiSrc,
	                      const ProgramGlobals::DirectionEnum systemOrEnviron,
	                      const TargetParamsType& tstStruct)
	{
		if (tstStruct.startingLoops().size()>0 &&
		        tstStruct.startingLoops()[indexOfOperator]>loopNumber)
			return;

		const bool hasBeenApplied = (phiNew.size() > 0);
		if (hasBeenApplied) return;

		VectorWithOffsetType phiOld = psiSrc;
		SizeType numberOfSites = targetHelper_.lrs().super().block().size();

		BorderEnumType corner = (site == 0 || site == numberOfSites -1) ?
		            ApplyOperatorType::BORDER_YES : ApplyOperatorType::BORDER_NO;

		PsimagLite::OstringStream msgg(std::cout.precision());
		PsimagLite::OstringStream::OstringStreamType& msg = msgg();
		msg<<"I'm applying a local operator now";
		progress_.printline(msgg, std::cout);

		const SizeType splitSize = targetHelper_.model().hilbertSize(site);

		typename PsimagLite::Vector<bool>::Type signs;
		targetHelper_.model().findOddElectronsOfOneSite(signs, site);
		FermionSign fs(targetHelper_.lrs().left(), signs);
		applyOpLocal_(phiNew,
		              phiOld,
		              tstStruct.aOperators()[indexOfOperator],
		              fs,
		              splitSize,
		              systemOrEnviron,
		              corner);

		RealType norma = norm(phiNew);
		if (norma<1e-6) {
			PsimagLite::OstringStream msgg2(std::cout.precision());
			PsimagLite::OstringStream::OstringStreamType& msg2 = msgg2();
			msg2<<"Norm of phi is zero\n";
			progress_.printline(msgg2, std::cout);
		}
	}

	void multiSitePush(DmrgSerializerType const* ds) const
	{
		const VectorWithOffsetType& psi00 = ensureOnlyOnePsi("multiSitePush");
		multiSiteExprHelper_.push(ds, psi00);
	}

	void wftSome(SizeType site, SizeType begin, SizeType end)
	{
		VectorVectorWithOffsetType& tvs = const_cast<VectorVectorWithOffsetType&>(targetVectors_);
		wftHelper_.wftSome(tvs, site, begin, end);
	}

	const VectorWithOffsetType& ensureOnlyOnePsi(PsimagLite::String func) const
	{
		if (psi_.size() != 1)
			err("ensureOnlyOnePsi failed (more than one excited); called from" +
			    func + "\n");

		if (psi_[0].size() != 1)
			err("ensureOnlyOnePsi failed (more than one sector); called from" +
			    func + "\n");

		return *(psi_[0][0]);
	}

	void timeHasAdvanced() { timeVectorsBase_->timeHasAdvanced(time_); }

	const ModelType& model() const { return targetHelper_.model(); }

private:

	// legacy reading, use only as fallback
	void loadEnergyLegacy(PsimagLite::IoSelector::In& io,
	                      PsimagLite::String label)
	{
		SizeType total = 0;
		io.read(total, label + "/Size");

		for (SizeType i = 0; i < total; ++i)
			io.read(E0_, label + "/" + ttos(i));
	}

	void checkOrder(SizeType i, const TargetParamsType& tstStruct) const
	{
		if (i==0) return;
		for (SizeType j=0;j<i;j++) {
			if (stage_[j] == StageEnum::DISABLED) {
				PsimagLite::String s ="TST:: Seeing dynamic site ";
				s += ttos(tstStruct.sites(i));
				s =s + " before having seen";
				s = s + " site "+ttos(tstStruct.sites(j));
				s = s +". Please order your dynamic sites in order of appearance.\n";
				throw PsimagLite::RuntimeError(s);
			}
		}
	}

	PsimagLite::String stageToString(SizeType i) const
	{
		switch (stage_[i]) {
		case StageEnum::DISABLED:
			return "Disabled";
		case StageEnum::OPERATOR:
			return "Applying operator for the first time";
		case StageEnum::WFT_NOADVANCE:
			return "WFT_NOADVANCE";
		case StageEnum::WFT_ADVANCE:
			return "WFT_ADVANCE";
		case StageEnum::COLLAPSE:
			return "COLLAPSE";
		}

		return "undefined";
	}

	SizeType evolve(SizeType i,
	                RealType Eg,
	                ProgramGlobals::DirectionEnum direction,
	                SizeType site,
	                SizeType loopNumber,
	                SizeType lastI,
	                const TargetParamsType& tstStruct)
	{
		SizeType advanceEach = tstStruct.advanceEach();

		if (direction == ProgramGlobals::DirectionEnum::INFINITE) {
			E0_ = Eg;
			return 0;
		}

		if (tstStruct.startingLoops().size()>0 &&
		        tstStruct.startingLoops()[i]>loopNumber) return 0;

		if (site != tstStruct.sites(i) && stage_[i] == StageEnum::DISABLED)
			return 0;

		if (site != tstStruct.sites(i) && stage_[i] != StageEnum::DISABLED && i>0)
			return 0;

		if (site == tstStruct.sites(i) && stage_[i] == StageEnum::DISABLED) {
			stage_[i] = StageEnum::OPERATOR;
		} else {
			stage_[i] = StageEnum::WFT_NOADVANCE;
		}

		if (stage_[i] == StageEnum::OPERATOR) checkOrder(i, tstStruct);

		const OptionsType& options = targetHelper_.model().params().options;
		const bool advanceOnlyAtBorder = !options.isSet("advanceUnrestricted");

		SizeType sites = targetHelper_.model().superGeometry().numberOfSites();
		bool weAreAtBorder = (site < 1 || site >= sites-1);
		bool dontAdvance = (advanceOnlyAtBorder & !weAreAtBorder);

		if (advanceEach > 0 && timesWithoutAdvancement_ >= advanceEach && !dontAdvance) {
			stage_[i] = StageEnum::WFT_ADVANCE;
			if (i == lastI) {
				++currentTimeStep_;
				timesWithoutAdvancement_ = 1;
				timeVectorsBase_->timeHasAdvanced(time_);
			}
		} else {
			if (i == lastI &&
			        stage_[i] == StageEnum::WFT_NOADVANCE &&
			        firstSeeLeftCorner_)
				++timesWithoutAdvancement_;
		}

		if (!firstSeeLeftCorner_ &&
		        i==lastI &&
		        stage_[i] == StageEnum::WFT_NOADVANCE &&
		        site==1)
			firstSeeLeftCorner_ = true;

		PsimagLite::OstringStream msgg2(std::cout.precision());
		PsimagLite::OstringStream::OstringStreamType& msg2 = msgg2();
		msg2<<"Steps without advance: "<<timesWithoutAdvancement_;
		msg2<<" site="<<site<<" currenTime="<<time();
		if (timesWithoutAdvancement_ > 0) progress_.printline(msgg2, std::cout);

		PsimagLite::OstringStream msgg(std::cout.precision());
		PsimagLite::OstringStream::OstringStreamType& msg = msgg();
		msg<<"Evolving, stage="<<stageToString(i);
		msg<<" site="<<site<<" loopNumber="<<loopNumber;
		msg<<" Eg="<<Eg;
		progress_.printline(msgg, std::cout);

		return 1;
	}

	void computePhi(SizeType i,
	                SizeType site,
	                VectorWithOffsetType& phiNew,
	                VectorWithOffsetType& phiOld,
	                const ProgramGlobals::DirectionEnum systemOrEnviron,
	                const TargetParamsType& tstStruct) const
	{
		SizeType numberOfSites = targetHelper_.lrs().super().block().size();

		if (stage_[i] == StageEnum::OPERATOR) {

			BorderEnumType corner = (tstStruct.sites(i)==0 ||
			                         tstStruct.sites(i)==numberOfSites -1) ?
			            ApplyOperatorType::BORDER_YES : ApplyOperatorType::BORDER_NO;

			PsimagLite::OstringStream msgg(std::cout.precision());
			PsimagLite::OstringStream::OstringStreamType& msg = msgg();
			msg<<"I'm applying a local operator now";
			progress_.printline(msgg, std::cout);
			typename PsimagLite::Vector<bool>::Type signs;
			targetHelper_.model().findOddElectronsOfOneSite(signs, site);

			const SizeType splitSize = targetHelper_.model().hilbertSize(site);
			FermionSign fs(targetHelper_.lrs().left(), signs);
			applyOpLocal_(phiNew,
			              phiOld,
			              tstStruct.aOperators()[i],
			              fs,
			              splitSize,
			              systemOrEnviron,corner);
			RealType norma = norm(phiNew);

			if (norma<1e-6) {
				PsimagLite::OstringStream msgg2(std::cout.precision());
				PsimagLite::OstringStream::OstringStreamType& msg2 = msgg2();
				msg2<<"Norm of phi is zero\n";
				progress_.printline(msgg2, std::cout);
			}
		} else if (stage_[i] == StageEnum::WFT_NOADVANCE ||
		           stage_[i] == StageEnum::WFT_ADVANCE) {
			const SizeType advanceEach = tstStruct.advanceEach();
			SizeType advance = indexNoAdvance_;

			if (advanceEach > 0 && stage_[i] == StageEnum::WFT_ADVANCE) {
				SizeType timeSteps = tstStruct.timeSteps();
				advance = (timeSteps > 0) ? timeSteps - 1 : 0;
			}

			if (targetVectors_.size() <= advance) {
				PsimagLite::String s(__FILE__);
				s += ": TargetVectors.size()" + ttos(targetVectors_.size());
				s += " but advance=" + ttos(advance) + "\n";
				throw PsimagLite::RuntimeError(s);
			}

			const VectorWithOffsetType& src = targetVectors_[advance];

			if (src.size() == 0) {
				PsimagLite::String s(__FILE__);
				s += ": TargetVectors[" + ttos(advance) + "].size()==0\n";
				throw PsimagLite::RuntimeError(s);
			}

			if (site==0 || site==numberOfSites -1)  {
				// don't wft since we did it before
				assert(advance < targetVectors_.size());
				phiNew = src;
				return;
			}

			wftHelper_.wftOneVector(phiNew, src, site);
		} else {
			throw PsimagLite::RuntimeError("computePhi\n");
		}
	}

	void clearPsi()
	{
		const SizeType sectors = psi_.size();
		for (SizeType i = 0; i < sectors; ++i) {
			const SizeType nexcited = psi_[i].size();
			for (SizeType j = 0; j < nexcited; ++j) {
				delete psi_[i][j];
				psi_[i][j] = 0;
			}
		}
	}

	ApplyOperatorExpression(const ApplyOperatorExpression&) = delete;

	ApplyOperatorExpression& operator=(const ApplyOperatorExpression&) = delete;

	PsimagLite::ProgressIndicator progress_;
	const TargetHelperType& targetHelper_;
	VectorStageEnumType stage_;
	RealType E0_;
	RealType time_;
	SizeType currentTimeStep_;
	SizeType indexNoAdvance_;
	ApplyOperatorType applyOpLocal_;
	VectorVectorVectorWithOffsetType psi_;
	VectorVectorWithOffsetType targetVectors_;
	TimeVectorsBaseType* timeVectorsBase_;
	WftHelperType wftHelper_;
	mutable MultiSiteExpressionHelperType multiSiteExprHelper_;
	CorrelationsSkeletonType correlationsSkel_;
	static SizeType timesWithoutAdvancement_;
	static bool firstSeeLeftCorner_;
};

template<typename T1, typename T2, typename T3>
SizeType ApplyOperatorExpression<T1,T2,T3>::timesWithoutAdvancement_ = 0;

template<typename T1, typename T2, typename T3>
bool ApplyOperatorExpression<T1,T2,T3>::firstSeeLeftCorner_ = false;
} // namespace Dmrg

#endif // APPLY_OP_EXPRESSION_H

