/*****************************************************************************
 * Project: RooFit                                                           *
 * Package: RooFitCore                                                       *
 * @(#)root/roofitcore:$Id$
 * Authors:                                                                  *
 *   WV, Wouter Verkerke, UC Santa Barbara, verkerke@slac.stanford.edu       *
 *   DK, David Kirkby,    UC Irvine,         dkirkby@uci.edu                 *
 *                                                                           *
 * Copyright (c) 2000-2005, Regents of the University of California          *
 *                          and Stanford University. All rights reserved.    *
 *                                                                           *
 * Redistribution and use in source and binary forms,                        *
 * with or without modification, are permitted according to the terms        *
 * listed in LICENSE (http://roofit.sourceforge.net/license.txt)             *
 *****************************************************************************/

//////////////////////////////////////////////////////////////////////////////
//
// BEGIN_HTML
// RooRealMPFE is the multi-processor front-end for parallel calculation
// of RooAbsReal objects. Each RooRealMPFE forks a process that calculates
// the value of the proxies RooAbsReal object. The (re)calculation of
// the proxied object is started asynchronously with the calculate() option.
// A subsequent call to getVal() will return the calculated value when available
// If the calculation is still in progress when getVal() is called it blocks
// the calling process until the calculation is done. The forked calculation process 
// is terminated when the front-end object is deleted
// Simple use demonstration
//
// <pre>
// RooAbsReal* slowFunc ;
//
// Double_t val = slowFunc->getVal() // Evaluate slowFunc in current process
//
// RooRealMPFE mpfe("mpfe","frontend to slowFunc",*slowFunc) ;
// mpfe.calculate() ;           // Start calculation of slow-func in remote process
//                              // .. do other stuff here ..
// Double_t val = mpfe.getVal() // Wait for remote calculation to finish and retrieve value
// </pre>
//
// END_HTML
//

#include "Riostream.h"
#include "RooFit.h"

#ifndef _WIN32
#include "BidirMMapPipe.h"
#endif

#include <cstdlib>
#include <sstream>
#include "RooRealMPFE.h"
#include "RooArgSet.h"
#include "RooAbsCategory.h"
#include "RooRealVar.h"
#include "RooCategory.h"
#include "RooMPSentinel.h"
#include "RooMsgService.h"
#include "RooNLLVar.h"
#include "RooTrace.h"

#include "TSystem.h"

RooMPSentinel RooRealMPFE::_sentinel ;

using namespace std;
using namespace RooFit;

ClassImp(RooRealMPFE)
  ;


//_____________________________________________________________________________
RooRealMPFE::RooRealMPFE(const char *name, const char *title, RooAbsReal& arg, Bool_t calcInline) : 
  RooAbsReal(name,title),
  _state(Initialize),
  _arg("arg","arg",this,arg),
  _vars("vars","vars",this),
  _calcInProgress(kFALSE),
  _verboseClient(kFALSE),
  _verboseServer(kFALSE),
  _inlineMode(calcInline),
  _remoteEvalErrorLoggingState(RooAbsReal::PrintErrors),
  _pipe(0),
  _updateMaster(0),
  _retrieveDispatched(kFALSE), _evalCarry(0.)
{  
  // Construct front-end object for object 'arg' whose evaluation will be calculated
  // asynchronously in a separate process. If calcInline is true the value of 'arg'
  // is calculate synchronously in the current process.
#ifdef _WIN32
  _inlineMode = kTRUE;
#endif
  initVars() ;
  _sentinel.add(*this) ;

}



//_____________________________________________________________________________
RooRealMPFE::RooRealMPFE(const RooRealMPFE& other, const char* name) : 
  RooAbsReal(other, name),
  _state(Initialize),
  _arg("arg",this,other._arg),
  _vars("vars",this,other._vars),
  _calcInProgress(kFALSE),
  _verboseClient(other._verboseClient),
  _verboseServer(other._verboseServer),
  _inlineMode(other._inlineMode),
  _forceCalc(other._forceCalc),
  _remoteEvalErrorLoggingState(other._remoteEvalErrorLoggingState),
  _pipe(0),
  _updateMaster(0),
  _retrieveDispatched(kFALSE), _evalCarry(other._evalCarry)
{
  // Copy constructor. Initializes in clean state so that upon eval
  // this instance will create its own server processes

  initVars() ;
  _sentinel.add(*this) ;
}



//_____________________________________________________________________________
RooRealMPFE::~RooRealMPFE() 
{
  // Destructor

  if (_state==Client) standby();
  _sentinel.remove(*this);
}



//_____________________________________________________________________________
void RooRealMPFE::initVars()
{
  // Initialize list of variables of front-end argument 'arg'

  // Empty current lists
  _vars.removeAll() ;
  _saveVars.removeAll() ;

  // Retrieve non-constant parameters
  RooArgSet* vars = _arg.arg().getParameters(RooArgSet()) ;
  //RooArgSet* ncVars = (RooArgSet*) vars->selectByAttrib("Constant",kFALSE) ;
  RooArgList varList(*vars) ;

  // Save in lists 
  _vars.add(varList) ;
  _saveVars.addClone(varList) ;
  _valueChanged.resize(_vars.getSize()) ;
  _constChanged.resize(_vars.getSize()) ;

  // Force next calculation
  _forceCalc = kTRUE ;

  delete vars ;
  //delete ncVars ;
}

Double_t RooRealMPFE::getCarry() const
{
  if (_inlineMode) {
    RooAbsTestStatistic* tmp = dynamic_cast<RooAbsTestStatistic*>(_arg.absArg());
    if (tmp) return tmp->getCarry();
    else return 0.;
  } else {
    return _evalCarry;
  }
}

//_____________________________________________________________________________
void RooRealMPFE::initialize() 
{
  // Initialize the remote process and message passing
  // pipes between current process and remote process

  // Trivial case: Inline mode 
  if (_inlineMode) {
    _state = Inline ;
    return ;
  }

#ifndef _WIN32
  // Clear eval error log prior to forking
  // to avoid confusions...
  clearEvalErrorLog() ;
  // Fork server process and setup IPC
  _pipe = new BidirMMapPipe();
  
  if (_pipe->isChild()) {
    // Start server loop 
    RooTrace::callgrind_zero() ;
    _state = Server ;
    serverLoop();

    // Kill server at end of service
    if (_verboseServer) ccoutD(Minimization) << "RooRealMPFE::initialize(" <<
	GetName() << ") server process terminating" << endl ;

    delete _arg.absArg();
    delete _pipe;
    _exit(0) ;
  } else {
    // Client process - fork successul
    if (_verboseClient) ccoutD(Minimization) << "RooRealMPFE::initialize(" <<
	GetName() << ") successfully forked server process " <<
	    _pipe->pidOtherEnd() << endl ;
    _state = Client ;
    _calcInProgress = kFALSE ;
  }
#endif // _WIN32
}



//_____________________________________________________________________________
void RooRealMPFE::serverLoop() 
{
  // Server loop of remote processes. This function will return
  // only when an incoming TERMINATE message is received.

#ifndef _WIN32
  int msg ;

  Int_t idx, index, numErrors ;
  Double_t value ;
  Bool_t isConst ;
  
  clearEvalErrorLog() ;

  while(*_pipe && !_pipe->eof()) {
    *_pipe >> msg;
    if (Terminate == msg) {
      if (_verboseServer) cout << "RooRealMPFE::serverLoop(" << GetName() 
			       << ") IPC fromClient> Terminate" << endl; 
      // send terminate acknowledged to client
      *_pipe << msg << BidirMMapPipe::flush;
      break;
    }

    switch (msg) {
    case SendReal:
      {
	*_pipe >> idx >> value >> isConst;
	if (_verboseServer) cout << "RooRealMPFE::serverLoop(" << GetName() 
				 << ") IPC fromClient> SendReal [" << idx << "]=" << value << endl ;       
	RooRealVar* rvar = (RooRealVar*)_vars.at(idx) ;
	rvar->setVal(value) ;
	if (rvar->isConstant() != isConst) {
	  rvar->setConstant(isConst) ;
	}
      }
      break ;

    case SendCat:
      {
	*_pipe >> idx >> index;
	if (_verboseServer) cout << "RooRealMPFE::serverLoop(" << GetName() 
				 << ") IPC fromClient> SendCat [" << idx << "]=" << index << endl ; 
	((RooCategory*)_vars.at(idx))->setIndex(index) ;
      }
      break ;

    case Calculate:
      if (_verboseServer) cout << "RooRealMPFE::serverLoop(" << GetName() 
			       << ") IPC fromClient> Calculate" << endl ;       
      _value = _arg ;
      break ;

    case CalculateNoOffset:
      if (_verboseServer) cout << "RooRealMPFE::serverLoop(" << GetName() 
			       << ") IPC fromClient> Calculate" << endl ; 

      RooAbsReal::setHideOffset(kFALSE) ;
      _value = _arg ; 
      RooAbsReal::setHideOffset(kTRUE) ;
      break ;

    case Retrieve:
      {
	if (_verboseServer) cout << "RooRealMPFE::serverLoop(" << GetName() 
				 << ") IPC fromClient> Retrieve" << endl ; 
	msg = ReturnValue;
	numErrors = numEvalErrors();
	*_pipe << msg << _value << getCarry() << numErrors;

	if (_verboseServer) cout << "RooRealMPFE::serverLoop(" << GetName() 
				 << ") IPC toClient> ReturnValue " << _value << " NumError " << numErrors << endl ; 

	if (numErrors) {
	  // Loop over errors
	  std::string objidstr;
	  {
	    ostringstream oss2;
	    // Format string with object identity as this cannot be evaluated on the other side
	    oss2 << "PID" << gSystem->GetPid() << "/";
	    printStream(oss2,kName|kClassName|kArgs,kInline);
	    objidstr = oss2.str();
	  }
	  std::map<const RooAbsArg*,pair<string,list<EvalError> > >::const_iterator iter = evalErrorIter();
	  const RooAbsArg* ptr = 0;
	  for (int i = 0; i < numEvalErrorItems(); ++i) {
	    list<EvalError>::const_iterator iter2 = iter->second.second.begin();
	    for (; iter->second.second.end() != iter2; ++iter2) {
	      ptr = iter->first;
	      *_pipe << ptr << iter2->_msg << iter2->_srvval << objidstr;
	      if (_verboseServer) cout << "RooRealMPFE::serverLoop(" << GetName() 
		<< ") IPC toClient> sending error log Arg " << iter->first << " Msg " << iter2->_msg << endl ; 
	    }
	  } 
	  // let other end know that we're done with the list of errors
	  ptr = 0;
	  *_pipe << ptr;
	  // Clear error list on local side
	  clearEvalErrorLog();
	}
	*_pipe << BidirMMapPipe::flush;
      }
      break;

    case ConstOpt:
      {
	Bool_t doTrack ;
	int code;
	*_pipe >> code >> doTrack;
	if (_verboseServer) cout << "RooRealMPFE::serverLoop(" << GetName() 
				 << ") IPC fromClient> ConstOpt " << code << " doTrack = " << (doTrack?"T":"F") << endl ; 
	((RooAbsReal&)_arg.arg()).constOptimizeTestStatistic(static_cast<RooAbsArg::ConstOpCode>(code),doTrack) ;
	break ;
      }

    case Verbose:
      {
      Bool_t flag ;
      *_pipe >> flag;
      if (_verboseServer) cout << "RooRealMPFE::serverLoop(" << GetName() 
			       << ") IPC fromClient> Verbose " << (flag?1:0) << endl ; 
      _verboseServer = flag ;
      }
      break ;

      
    case ApplyNLLW2:
      {
      Bool_t flag ;
      *_pipe >> flag;
      if (_verboseServer) cout << "RooRealMPFE::serverLoop(" << GetName() 
			       << ") IPC fromClient> ApplyNLLW2 " << (flag?1:0) << endl ; 
      
      // Do application of weight-squared here
      doApplyNLLW2(flag) ;
      }
      break ;

    case EnableOffset:
      {
      Bool_t flag ;
      *_pipe >> flag;
      if (_verboseServer) cout << "RooRealMPFE::serverLoop(" << GetName() 
			       << ") IPC fromClient> EnableOffset " << (flag?1:0) << endl ; 
      
      // Enable likelihoof offsetting here
      ((RooAbsReal&)_arg.arg()).enableOffsetting(flag) ;
      }
      break ;

    case LogEvalError:
      {
	int iflag2;
	*_pipe >> iflag2;
	RooAbsReal::ErrorLoggingMode flag2 = static_cast<RooAbsReal::ErrorLoggingMode>(iflag2);
	RooAbsReal::setEvalErrorLoggingMode(flag2) ;
	if (_verboseServer) cout << "RooRealMPFE::serverLoop(" << GetName() 
				 << ") IPC fromClient> LogEvalError flag = " << flag2 << endl ;       
      }
      break ;


    default:
      if (_verboseServer) cout << "RooRealMPFE::serverLoop(" << GetName() 
			       << ") IPC fromClient> Unknown message (code = " << msg << ")" << endl ; 
      break ;
    }
  }

#endif // _WIN32
}



//_____________________________________________________________________________
void RooRealMPFE::calculate() const 
{
  // Client-side function that instructs server process to start
  // asynchronuous (re)calculation of function value. This function
  // returns immediately. The calculated value can be retrieved
  // using getVal()


  // Start asynchronous calculation of arg value
  if (_state==Initialize) {
    //     cout << "RooRealMPFE::calculate(" << GetName() << ") initializing" << endl ;
    const_cast<RooRealMPFE*>(this)->initialize() ;
  }

  // Inline mode -- Calculate value now
  if (_state==Inline) {
    //     cout << "RooRealMPFE::calculate(" << GetName() << ") performing Inline calculation NOW" << endl ;
    _value = _arg ;
    clearValueDirty() ;
  }

#ifndef _WIN32
  // Compare current value of variables with saved values and send changes to server
  if (_state==Client) {
    //     cout << "RooRealMPFE::calculate(" << GetName() << ") state is Client trigger remote calculation" << endl ;
    Int_t i(0) ;
    RooFIter viter = _vars.fwdIterator() ;
    RooFIter siter = _saveVars.fwdIterator() ;
    
    //for (i=0 ; i<_vars.getSize() ; i++) {
    RooAbsArg *var, *saveVar ;
    while((var = viter.next())) {
      saveVar = siter.next() ;

      //Bool_t valChanged = !(*var==*saveVar) ;      
      Bool_t valChanged,constChanged  ;
      if (!_updateMaster) {
	valChanged = !var->isIdentical(*saveVar,kTRUE) ;
	constChanged = (var->isConstant() != saveVar->isConstant()) ;	       
	_valueChanged[i] = valChanged ; 
	_constChanged[i] = constChanged ; 
      } else {
	valChanged = _updateMaster->_valueChanged[i] ;
	constChanged = _updateMaster->_constChanged[i] ;
      }

      if ( valChanged || constChanged || _forceCalc) {	
	//cout << "RooRealMPFE::calculate(" << GetName() << " variable " << var->GetName() << " changed " << endl ;
	if (_verboseClient) cout << "RooRealMPFE::calculate(" << GetName()
				 << ") variable " << _vars.at(i)->GetName() << " changed" << endl ;
	if (constChanged) {
	  ((RooRealVar*)saveVar)->setConstant(var->isConstant()) ;
	}
	saveVar->copyCache(var) ;
	
	// send message to server
	if (dynamic_cast<RooAbsReal*>(var)) {
	  int msg = SendReal ;
	  Double_t val = ((RooAbsReal*)var)->getVal() ;
	  Bool_t isC = var->isConstant() ;
	  *_pipe << msg << i << val << isC;

	  if (_verboseServer) cout << "RooRealMPFE::calculate(" << GetName() 
				   << ") IPC toServer> SendReal [" << i << "]=" << val << (isC?" (Constant)":"") <<  endl ;
	} else if (dynamic_cast<RooAbsCategory*>(var)) {
	  int msg = SendCat ;
	  UInt_t idx = ((RooAbsCategory*)var)->getIndex() ;
	  *_pipe << msg << i << idx;
	  if (_verboseServer) cout << "RooRealMPFE::calculate(" << GetName() 
				   << ") IPC toServer> SendCat [" << i << "]=" << idx << endl ;
	}
      }
      i++ ;
    }

    int msg = hideOffset() ? Calculate : CalculateNoOffset;
    *_pipe << msg;
    if (_verboseServer) cout << "RooRealMPFE::calculate(" << GetName() 
			     << ") IPC toServer> Calculate " << endl ;

    // Clear dirty state and mark that calculation request was dispatched
    clearValueDirty() ;
    _calcInProgress = kTRUE ;
    _forceCalc = kFALSE ;

    msg = Retrieve ;
    *_pipe << msg << BidirMMapPipe::flush;
    if (_verboseServer) cout << "RooRealMPFE::evaluate(" << GetName() 
			     << ") IPC toServer> Retrieve " << endl ;    
    _retrieveDispatched = kTRUE ;        

  } else if (_state!=Inline) {
    cout << "RooRealMPFE::calculate(" << GetName() 
	 << ") ERROR not in Client or Inline mode" << endl ;
  }

  
#endif // _WIN32
}




//_____________________________________________________________________________
Double_t RooRealMPFE::getValV(const RooArgSet* /*nset*/) const 
{
  // If value needs recalculation and calculation has not beed started
  // with a call to calculate() start it now. This function blocks
  // until remote process has finished calculation and returns
  // remote value
  

  if (isValueDirty()) {
    // Cache is dirty, no calculation has been started yet
    //cout << "RooRealMPFE::getValF(" << GetName() << ") cache is dirty, caling calculate and evaluate" << endl ;
    calculate() ;
    _value = evaluate() ;
  } else if (_calcInProgress) {
    //cout << "RooRealMPFE::getValF(" << GetName() << ") calculation in progress, calling evaluate" << endl ;
    // Cache is clean and calculation is in progress
    _value = evaluate() ;    
  } else {
    //cout << "RooRealMPFE::getValF(" << GetName() << ") cache is clean, doing nothing" << endl ;
    // Cache is clean and calculated value is in cache
  }

//   cout << "RooRealMPFE::getValV(" << GetName() << ") value = " << Form("%5.10f",_value) << endl ;
  return _value ;  
}



//_____________________________________________________________________________
Double_t RooRealMPFE::evaluate() const
{
  // Send message to server process to retrieve output value
  // If error were logged use logEvalError() on remote side
  // transfer those errors to the local eval error queue.

  // Retrieve value of arg
  Double_t return_value = 0;
  if (_state==Inline) {
    return_value = _arg ; 
  } else if (_state==Client) {
#ifndef _WIN32
    bool needflush = false;
    int msg;
    Double_t value;

    // If current error loggin state is not the same as remote state
    // update the remote state
    if (evalErrorLoggingMode() != _remoteEvalErrorLoggingState) {
      msg = LogEvalError ;
      RooAbsReal::ErrorLoggingMode flag = evalErrorLoggingMode() ;
      *_pipe << msg << flag;
      needflush = true;
      _remoteEvalErrorLoggingState = evalErrorLoggingMode() ;
    }

    if (!_retrieveDispatched) {
      msg = Retrieve ;
      *_pipe << msg;
      needflush = true;
      if (_verboseServer) cout << "RooRealMPFE::evaluate(" << GetName() 
			       << ") IPC toServer> Retrieve " << endl ;    
    }
    if (needflush) *_pipe << BidirMMapPipe::flush;
    _retrieveDispatched = kFALSE ;


    Int_t numError;

    *_pipe >> msg >> value >> _evalCarry >> numError;
    
    if (msg!=ReturnValue) {
      cout << "RooRealMPFE::evaluate(" << GetName() 
	   << ") ERROR: unexpected message from server process: " << msg << endl ;
      return 0 ;
    }
    if (_verboseServer) cout << "RooRealMPFE::evaluate(" << GetName() 
			     << ") IPC fromServer> ReturnValue " << value << endl ;

    if (_verboseServer) cout << "RooRealMPFE::evaluate(" << GetName() 
			     << ") IPC fromServer> NumErrors " << numError << endl ;
    if (numError) {
      // Retrieve remote errors and feed into local error queue
      char *msgbuf1 = 0, *msgbuf2 = 0, *msgbuf3 = 0;
      RooAbsArg *ptr = 0;
      while (true) {
	*_pipe >> ptr;
	if (!ptr) break;
	*_pipe >> msgbuf1 >> msgbuf2 >> msgbuf3;
	if (_verboseServer) cout << "RooRealMPFE::evaluate(" << GetName() 
	  << ") IPC fromServer> retrieving error log Arg " << ptr << " Msg " << msgbuf1 << endl ;    

	logEvalError(reinterpret_cast<RooAbsReal*>(ptr),msgbuf3,msgbuf1,msgbuf2) ;
      }
      std::free(msgbuf1);
      std::free(msgbuf2);
      std::free(msgbuf3);
    }

    // Mark end of calculation in progress 
    _calcInProgress = kFALSE ;
    return_value = value ;
#endif // _WIN32
  }

  return return_value;
}



//_____________________________________________________________________________
void RooRealMPFE::standby()
{
  // Terminate remote server process and return front-end class
  // to standby mode. Calls to calculate() or evaluate() after
  // this call will automatically recreated the server process.

#ifndef _WIN32
  if (_state==Client) {
    if (_pipe->good()) {
      // Terminate server process ;
      if (_verboseServer) cout << "RooRealMPFE::standby(" << GetName() 
	<< ") IPC toServer> Terminate " << endl; 
      int msg = Terminate;
      *_pipe << msg << BidirMMapPipe::flush;
      // read handshake
      msg = 0;
      *_pipe >> msg;
      if (Terminate != msg || 0 != _pipe->close()) {
	std::cerr << "In " << __func__ << "(" << __FILE__ ", " << __LINE__ <<
	  "): Server shutdown failed." << std::endl;
      }
    } else {
      if (_verboseServer) {
	std::cerr << "In " << __func__ << "(" << __FILE__ ", " <<
	  __LINE__ << "): Pipe has already shut down, not sending "
	  "Terminate to server." << std::endl;
      }
    }
    // Close pipes
    delete _pipe;
    _pipe = 0;
    
    // Revert to initialize state 
    _state = Initialize;
  }
#endif // _WIN32
}



//_____________________________________________________________________________
void RooRealMPFE::constOptimizeTestStatistic(ConstOpCode opcode, Bool_t doAlsoTracking) 
{
  // Intercept call to optimize constant term in test statistics
  // and forward it to object on server side.

#ifndef _WIN32
  if (_state==Client) {

    int msg = ConstOpt ;
    int op = opcode;
    *_pipe << msg << op << doAlsoTracking;
    if (_verboseServer) cout << "RooRealMPFE::constOptimize(" << GetName() 
			     << ") IPC toServer> ConstOpt " << opcode << endl ;  

    initVars() ;
  }
#endif // _WIN32

  if (_state==Inline) {
    ((RooAbsReal&)_arg.arg()).constOptimizeTestStatistic(opcode,doAlsoTracking) ;
  }
}



//_____________________________________________________________________________
void RooRealMPFE::setVerbose(Bool_t clientFlag, Bool_t serverFlag) 
{
  // Control verbose messaging related to inter process communication
  // on both client and server side

#ifndef _WIN32
  if (_state==Client) {
    int msg = Verbose ;
    *_pipe << msg << serverFlag;
    if (_verboseServer) cout << "RooRealMPFE::setVerbose(" << GetName() 
			     << ") IPC toServer> Verbose " << (serverFlag?1:0) << endl ;      
  }
#endif // _WIN32
  _verboseClient = clientFlag ; _verboseServer = serverFlag ;
}


//_____________________________________________________________________________
void RooRealMPFE::applyNLLWeightSquared(Bool_t flag) 
{
  // Control verbose messaging related to inter process communication
  // on both client and server side

#ifndef _WIN32
  if (_state==Client) {
    int msg = ApplyNLLW2 ;
    *_pipe << msg << flag;
    if (_verboseServer) cout << "RooRealMPFE::applyNLLWeightSquared(" << GetName() 
			     << ") IPC toServer> ApplyNLLW2 " << (flag?1:0) << endl ;      
  } 
#endif // _WIN32
  doApplyNLLW2(flag) ;
}


//_____________________________________________________________________________
void RooRealMPFE::doApplyNLLW2(Bool_t flag) 
{
  RooNLLVar* nll = dynamic_cast<RooNLLVar*>(_arg.absArg()) ;
  if (nll) {
    nll->applyWeightSquared(flag) ;
  }  
}


//_____________________________________________________________________________
void RooRealMPFE::enableOffsetting(Bool_t flag) 
{
  // Control verbose messaging related to inter process communication
  // on both client and server side

#ifndef _WIN32
  if (_state==Client) {
    int msg = EnableOffset ;
    *_pipe << msg << flag;
    if (_verboseServer) cout << "RooRealMPFE::enableOffsetting(" << GetName() 
			     << ") IPC toServer> EnableOffset " << (flag?1:0) << endl ;      
  } 
#endif // _WIN32
  ((RooAbsReal&)_arg.arg()).enableOffsetting(flag) ;
}