RooFormulaVar.cxx

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/*****************************************************************************
 * 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)             *
 *****************************************************************************/
 
//////////////////////////////////////////////////////////////////////////////
/// \class RooFormulaVar
///
/// A RooFormulaVar is a generic implementation of a real-valued object,
/// which takes a RooArgList of servers and a C++ expression string defining how
/// its value should be calculated from the given list of servers.
/// RooFormulaVar uses a RooFormula object to perform the expression evaluation.
///
/// If RooAbsPdf objects are supplied to RooFormulaVar as servers, their
/// raw (unnormalized) values will be evaluated. Use RooGenericPdf, which
/// constructs generic PDF functions, to access their properly normalized
/// values.
///
/// The string expression can be any valid TFormula expression referring to the
/// listed servers either by name or by their ordinal list position. These three are
/// equivalent:
/// ```
///   RooFormulaVar("gen", "x*y", RooArgList(x,y))       // reference by name
///   RooFormulaVar("gen", "@0*@1", RooArgList(x,y))     // reference by ordinal with @
///   RooFormulaVar("gen", "x[0]*x[1]", RooArgList(x,y)) // TFormula-builtin reference by ordinal
/// ```
/// Note that `x[i]` is an expression reserved for TFormula. All variable references
/// are automatically converted to the TFormula-native format. If a variable with
/// the name `x` is given, the RooFormula interprets `x[i]` as a list position,
/// but `x` without brackets as the name of a RooFit object.
///
/// The last two versions, while slightly less readable, are more versatile because
/// the names of the arguments are not hard coded.
///
 
 
#include "Riostream.h"
 
#include "RooFormulaVar.h"
#include "RooStreamParser.h"
#include "RooMsgService.h"
#include "RooFormula.h"
#include "RooAbsRealLValue.h"
#include "RooAbsBinning.h"
#include "RooCurve.h"
#include "RooFitImplHelpers.h"
 
#ifdef ROOFIT_LEGACY_EVAL_BACKEND
#include "RooNLLVar.h"
#include "RooChi2Var.h"
#endif
 
using std::ostream, std::istream, std::list;
 
 
RooFormulaVar::RooFormulaVar() {}
 
RooFormulaVar::~RooFormulaVar()
{
   if(_formula) delete _formula;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Constructor with formula expression and list of input variables.
/// \param[in] name Name of the formula.
/// \param[in] title Title of the formula.
/// \param[in] inFormula Expression to be evaluated.
/// \param[in] dependents Variables that should be passed to the formula.
/// \param[in] checkVariables Check that all variables from `dependents` are used in the expression.
RooFormulaVar::RooFormulaVar(const char *name, const char *title, const char* inFormula, const RooArgList& dependents,
    bool checkVariables) :
  RooAbsReal(name,title),
  _actualVars("actualVars","Variables used by formula expression",this),
  _formExpr(inFormula)
{
  if (dependents.empty()) {
    _value = traceEval(nullptr);
  } else {
    _formula = new RooFormula(GetName(), _formExpr, dependents, checkVariables);
    _formExpr = _formula->reindexedFormulaForUsedVars().c_str();
    _actualVars.add(_formula->actualDependents());
  }
}
 
 
 
////////////////////////////////////////////////////////////////////////////////
/// Constructor with formula expression, title and list of input variables.
/// \param[in] name Name of the formula.
/// \param[in] title Formula expression. Will also be used as the title.
/// \param[in] dependents Variables that should be passed to the formula.
/// \param[in] checkVariables Check that all variables from `dependents` are used in the expression.
RooFormulaVar::RooFormulaVar(const char *name, const char *title, const RooArgList& dependents,
    bool checkVariables) :
  RooAbsReal(name,title),
  _actualVars("actualVars","Variables used by formula expression",this),
  _formExpr(title)
{
  if (dependents.empty()) {
    _value = traceEval(nullptr);
  } else {
    _formula = new RooFormula(GetName(), _formExpr, dependents, checkVariables);
    _formExpr = _formula->reindexedFormulaForUsedVars().c_str();
    _actualVars.add(_formula->actualDependents());
  }
}
 
 
 
////////////////////////////////////////////////////////////////////////////////
/// Copy constructor
 
RooFormulaVar::RooFormulaVar(const RooFormulaVar& other, const char* name) :
  RooAbsReal(other, name),
  _actualVars("actualVars",this,other._actualVars),
  _formExpr(other._formExpr)
{
   for (auto const &item : other._binnings) {
      _binnings[item.first] = std::unique_ptr<RooAbsBinning>{item.second->clone()};
   }
  if (other._formula && other._formula->ok()) {
    _formula = new RooFormula(*other._formula);
    _formExpr = _formula->reindexedFormulaForUsedVars().c_str();
  }
}
 
 
////////////////////////////////////////////////////////////////////////////////
/// Return reference to internal RooFormula object.
/// If it doesn't exist, create it on the fly.
RooFormula& RooFormulaVar::getFormula() const
{
  if (!_formula) {
    // After being read from file, the formula object might not exist, yet:
    _formula = new RooFormula(GetName(), _formExpr, _actualVars);
    const_cast<TString &>(_formExpr) = _formula->reindexedFormulaForUsedVars().c_str();
  }
 
  return *_formula;
}
 
 
bool RooFormulaVar::ok() const { return getFormula().ok() ; }
 
 
void RooFormulaVar::dumpFormula() { getFormula().printMultiline(std::cout, 0) ; }
 
 
////////////////////////////////////////////////////////////////////////////////
/// Calculate current value of object from internal formula
 
double RooFormulaVar::evaluate() const
{
  return getFormula().eval(_actualVars.nset());
}
 
 
void RooFormulaVar::doEval(RooFit::EvalContext &ctx) const
{
   getFormula().doEval(_actualVars, ctx);
}
 
 
////////////////////////////////////////////////////////////////////////////////
/// Propagate server change information to embedded RooFormula object
 
bool RooFormulaVar::redirectServersHook(const RooAbsCollection& newServerList, bool mustReplaceAll, bool nameChange, bool isRecursive)
{
  bool error = getFormula().changeDependents(newServerList,mustReplaceAll,nameChange);
 
  _formExpr = getFormula().reindexedFormulaForUsedVars().c_str();
  return error || RooAbsReal::redirectServersHook(newServerList, mustReplaceAll, nameChange, isRecursive);
}
 
 
 
////////////////////////////////////////////////////////////////////////////////
/// Print info about this object to the specified stream.
 
void RooFormulaVar::printMultiline(ostream& os, Int_t contents, bool verbose, TString indent) const
{
  RooAbsReal::printMultiline(os,contents,verbose,indent);
  if(verbose) {
    indent.Append("  ");
    os << indent;
    getFormula().printMultiline(os,contents,verbose,indent);
  }
}
 
 
 
////////////////////////////////////////////////////////////////////////////////
/// Add formula expression as meta argument in printing interface
 
void RooFormulaVar::printMetaArgs(ostream& os) const
{
  os << "formula=\"" << _formExpr << "\" " ;
}
 
 
 
 
////////////////////////////////////////////////////////////////////////////////
/// Read object contents from given stream
 
bool RooFormulaVar::readFromStream(istream& /*is*/, bool /*compact*/, bool /*verbose*/)
{
  coutE(InputArguments) << "RooFormulaVar::readFromStream(" << GetName() << "): can't read" << std::endl ;
  return true ;
}
 
 
 
////////////////////////////////////////////////////////////////////////////////
/// Write object contents to given stream
 
void RooFormulaVar::writeToStream(ostream& os, bool compact) const
{
  if (compact) {
    std::cout << getVal() << std::endl ;
  } else {
    os << GetTitle() ;
  }
}
 
////////////////////////////////////////////////////////////////////////////////
/// Declare that this function is piecewise constant (flat) within the bins of
/// the given `binning` of the observable `obs`, which must be one of the formula
/// variables. The method can be called several times to set a binning for more
/// than one observable. See RooGenericPdf::setBinning() for details.
 
void RooFormulaVar::setBinning(const RooAbsRealLValue &obs, const RooAbsBinning &binning, bool checkFlatness)
{
   // Match the observable to a formula variable by name, so that a same-named
   // stand-in for the actual server is accepted too.
   const int idx = _actualVars.index(obs.GetName());
   if (idx < 0) {
      coutE(InputArguments) << "RooFormulaVar::setBinning(" << GetName() << ") the observable " << obs.GetName()
                            << " is not one of the formula variables of this function, nothing done." << std::endl;
      return;
   }
 
   if (checkFlatness) {
      // Sample the function by varying the actual formula variable (the server),
      // which may be a different object than `obs` if `obs` is just a same-named
      // stand-in: the function's value depends on the server, not on `obs`.
      if (auto *serverObs = dynamic_cast<RooAbsRealLValue *>(_actualVars.at(idx))) {
         std::span<const double> boundaries{binning.array(), static_cast<std::size_t>(binning.numBoundaries())};
         if (!RooHelpers::isFunctionFlatInBins(*this, *serverObs, boundaries)) {
            coutE(InputArguments) << "RooFormulaVar::setBinning(" << GetName() << ") the expression \"" << _formExpr
                                  << "\" is not flat within the given bins of " << obs.GetName()
                                  << ". The binning is not set. Pass checkFlatness=false to override this check."
                                  << std::endl;
            return;
         }
      }
   }
 
   // Key the binning by the observable's index in _actualVars (not its name), so
   // that it survives a renaming of the variable or a server redirection.
   _binnings[idx] = std::unique_ptr<RooAbsBinning>{binning.clone()};
}
 
////////////////////////////////////////////////////////////////////////////////
/// Return the binning previously declared with setBinning() for observable
/// `obs`, or nullptr if no binning was declared. This reports only binnings
/// owned by this formula, not binning hints forwarded by its servers.
 
const RooAbsBinning *RooFormulaVar::getBinning(const RooAbsRealLValue &obs) const
{
   auto found = _binnings.find(_actualVars.index(obs.GetName()));
   return found != _binnings.end() ? found->second.get() : nullptr;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Remove a binning previously declared with setBinning() for observable `obs`,
/// reverting to the generic numeric integrator for it. Returns true if a binning
/// was removed, false if none was set for `obs`.
 
bool RooFormulaVar::removeBinning(const RooAbsRealLValue &obs)
{
   return _binnings.erase(_actualVars.index(obs.GetName())) > 0;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Return true if a binning was set with setBinning() for every
/// observable in the integration set `obs`.
 
bool RooFormulaVar::isBinnedDistribution(const RooArgSet &obs) const
{
   if (obs.empty() || _binnings.empty()) {
      return false;
   }
   for (RooAbsArg *o : obs) {
      const int idx = _actualVars.index(o->GetName());
      // Observables that are not formula variables of this function are ones we
      // do not depend on: the function is constant (hence trivially binned) in
      // them, so they must be ignored here. This matches the convention that
      // composite functions like RooProduct rely on, where each component's
      // isBinnedDistribution() is queried with the full observable set.
      if (idx < 0) {
         continue;
      }
      if (_binnings.find(idx) == _binnings.end()) {
         return false;
      }
   }
   return true;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Return the boundaries of the binning set with setBinning() that fall
/// within [xlo, xhi]. If no binning was set for this observable, forward the bin
/// boundaries from the server that defines the observable obs.
 
std::list<double>* RooFormulaVar::binBoundaries(RooAbsRealLValue& obs, double xlo, double xhi) const
{
   auto found = _binnings.find(_actualVars.index(obs.GetName()));
   if (found != _binnings.end()) {
      const RooAbsBinning &binning = *found->second;
      auto hint = new std::list<double>;
      for (int i = 0; i < binning.numBoundaries(); ++i) {
         const double boundary = binning.array()[i];
         if (boundary >= xlo && boundary <= xhi) {
            hint->push_back(boundary);
         }
      }
      return hint;
   }
 
  for (const auto par : _actualVars) {
    auto func = static_cast<const RooAbsReal*>(par);
    list<double>* binb = nullptr;
 
    if (func && (binb = func->binBoundaries(obs,xlo,xhi)) ) {
      return binb;
    }
  }
 
  return nullptr;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Return sampling hints that draw the piecewise-flat shape exactly if a binning
/// was set for this observable. Otherwise, forward the plot sampling hint from
/// the server that defines the observable obs.
 
std::list<double>* RooFormulaVar::plotSamplingHint(RooAbsRealLValue& obs, double xlo, double xhi) const
{
   if (const RooAbsBinning *binning = getBinning(obs)) {
      return RooCurve::plotSamplingHintForBinBoundaries(
         {binning->array(), static_cast<std::size_t>(binning->numBoundaries())}, xlo, xhi);
   }
 
  for (const auto par : _actualVars) {
    auto func = dynamic_cast<const RooAbsReal*>(par);
    list<double>* hint = nullptr;
 
    if (func && (hint = func->plotSamplingHint(obs,xlo,xhi)) ) {
      return hint;
    }
  }
 
  return nullptr;
}
 
 
 
////////////////////////////////////////////////////////////////////////////////
/// Return the default error level for MINUIT error analysis
/// If the formula contains one or more RooNLLVars and
/// no RooChi2Vars, return the defaultErrorLevel() of
/// RooNLLVar. If the addition contains one ore more RooChi2Vars
/// and no RooNLLVars, return the defaultErrorLevel() of
/// RooChi2Var. If the addition contains neither or both
/// issue a warning message and return a value of 1
 
double RooFormulaVar::defaultErrorLevel() const
{
  RooAbsReal* nllArg(nullptr) ;
  RooAbsReal* chi2Arg(nullptr) ;
 
#ifdef ROOFIT_LEGACY_EVAL_BACKEND
  for (const auto arg : _actualVars) {
    if (dynamic_cast<RooNLLVar*>(arg)) {
      nllArg = static_cast<RooAbsReal*>(arg) ;
    }
    if (dynamic_cast<RooChi2Var*>(arg)) {
      chi2Arg = static_cast<RooAbsReal*>(arg) ;
    }
  }
#endif
 
  if (nllArg && !chi2Arg) {
    coutI(Minimization) << "RooFormulaVar::defaultErrorLevel(" << GetName()
         << ") Formula contains a RooNLLVar, using its error level" << std::endl ;
    return nllArg->defaultErrorLevel() ;
  } else if (chi2Arg && !nllArg) {
    coutI(Minimization) << "RooFormulaVar::defaultErrorLevel(" << GetName()
    << ") Formula contains a RooChi2Var, using its error level" << std::endl ;
    return chi2Arg->defaultErrorLevel() ;
  } else if (!nllArg && !chi2Arg) {
    coutI(Minimization) << "RooFormulaVar::defaultErrorLevel(" << GetName() << ") WARNING: "
            << "Formula contains neither RooNLLVar nor RooChi2Var server, using default level of 1.0" << std::endl ;
  } else {
    coutI(Minimization) << "RooFormulaVar::defaultErrorLevel(" << GetName() << ") WARNING: "
         << "Formula contains BOTH RooNLLVar and RooChi2Var server, using default level of 1.0" << std::endl ;
  }
 
  return 1.0 ;
}
 
std::string RooFormulaVar::getUniqueFuncName() const
{
   return getFormula().getTFormula()->GetUniqueFuncName().Data();
}
 
std::unique_ptr<RooAbsArg>
RooFormulaVar::compileForNormSet(RooArgSet const &normSet, RooFit::Detail::CompileContext &ctx) const
{
   // Some users exploit unnormalized RooAbsPdfs as inputs for RooFormulaVars,
   // relying on what the pdf returns from RooAbsPdf::evaluate(). This is in
   // principle not allowed because every pdf needs to be evaluated with a
   // normalization set, but it's so common in user code that we need to
   // support it. To make this work, we need to make sure that the no
   // normalization over non-dependents is happening at this point, reducing
   // the normalization set to the subset of actual dependents.
   // See also the "PdfAsFunctionInFormulaVar" test in testRooAbsPdf.
   RooArgSet depList;
   getObservables(&normSet, depList);
   auto newArg = std::unique_ptr<RooAbsArg>{static_cast<RooAbsArg *>(Clone())};
   ctx.markAsCompiled(*newArg);
   ctx.compileServers(*newArg, depList);
   return newArg;
}