[RF] Upstream from CMS Combine functions relevant for parameter freezing

Upstream from CMS Combine functions relevant for parameter freezing when
using RooMultiPdfs.

Author: guitargeek

roofit/roofitcore/inc/RooAbsCollection.h

@@ -362,6 +362,8 @@ class RooAbsCollection : public TObject, public RooPrintable {
 
   void useHashMapForFind(bool flag) const;
 
+  void removeConstantParameters();
+
   // For use in the RooArgList/Set(std::vector<RooAbsArgPtrOrDouble> const&) constructor.
   // Can be replaced with std::variant when C++17 is the minimum supported standard.
   struct RooAbsArgPtrOrDouble {

roofit/roofitcore/inc/RooHelpers.h

@@ -88,6 +88,11 @@ void checkRangeOfParameters(const RooAbsReal *callingClass, std::initializer_lis
                             double max = std::numeric_limits<double>::max(), bool limitsInAllowedRange = false,
                             std::string const &extraMessage = "");
 
+/// set all RooRealVars to constants. return true if at least one changed status
+bool setAllConstant(const RooAbsCollection &coll, bool constant = true);
+
+bool freezeAllDisassociatedRooMultiPdfParameters(const RooArgSet &multiPdfs, const RooArgSet &allRooMultiPdfParams,
+                                                 bool freeze = true, bool freezeDisassParams_verb = false);
 
 } // namespace RooHelpers
 

roofit/roofitcore/src/RooAbsCollection.cxx

@@ -1646,3 +1646,13 @@ void RooAbsCollection::throwAddTypedException(TClass *klass, RooAbsArg *arg)
    oocoutE(nullptr, InputArguments) << msg.str() << std::endl;
    throw std::invalid_argument(msg.str());
 }
+
+void RooAbsCollection::removeConstantParameters()
+{
+   RooArgSet constSet;
+   for (auto const *myarg : static_range_cast<RooRealVar *>(*this)) {
+      if (myarg->isConstant())
+         constSet.add(*myarg);
+   }
+   this->remove(constSet);
+}

roofit/roofitcore/src/RooHelpers.cxx

@@ -17,10 +17,13 @@
 #include <RooAbsPdf.h>
 #include <RooAbsRealLValue.h>
 #include <RooArgList.h>
+#include <RooCategory.h>
 #include <RooDataHist.h>
 #include <RooDataSet.h>
+#include <RooMultiPdf.h>
 #include <RooProdPdf.h>
 #include <RooRealSumPdf.h>
+#include <RooRealVar.h>
 #include <RooSimultaneous.h>
 
 #include <ROOT/StringUtils.hxx>
@@ -148,4 +151,59 @@ void checkRangeOfParameters(const RooAbsReal *callingClass, std::initializer_lis
    }
 }
 
+bool setAllConstant(const RooAbsCollection &coll, bool constant)
+{
+   bool changed = false;
+   for (RooAbsArg *a : coll) {
+      RooRealVar *v = dynamic_cast<RooRealVar *>(a);
+      RooCategory *cv = dynamic_cast<RooCategory *>(a);
+      if (v && (v->isConstant() != constant)) {
+         changed = true;
+         v->setConstant(constant);
+      } else if (cv && (cv->isConstant() != constant)) {
+         changed = true;
+         cv->setConstant(constant);
+      }
+   }
+   return changed;
+}
+
+bool freezeAllDisassociatedRooMultiPdfParameters(const RooArgSet &multiPdfs, const RooArgSet &allRooMultiPdfParams,
+                                                 bool freeze, bool freezeDisassParams_verb)
+{
+   RooArgSet multiPdfParams(allRooMultiPdfParams);
+
+   // For each multiPdf, get the active pdf and remove its parameters
+   // from this list of params and then freeze the remaining ones
+
+   for (RooAbsArg *P : multiPdfs) {
+      RooMultiPdf *mpdf = dynamic_cast<RooMultiPdf *>(P);
+      RooAbsPdf *pdf = (RooAbsPdf *)mpdf->getCurrentPdf();
+      if (freezeDisassParams_verb) {
+         std::cout << " Current active PDF - " << pdf->GetName() << std::endl;
+      }
+      std::unique_ptr<RooArgSet> pdfPars(pdf->getParameters((const RooArgSet *)0));
+      pdfPars->removeConstantParameters(); // make sure still to ignore user set constants
+      multiPdfParams.remove(*pdfPars);
+   }
+
+   if (multiPdfParams.getSize() > 0) {
+      if (freezeDisassParams_verb) {
+         std::cout << " Going to " << (freeze ? " freeze " : " float ") << " the following (disassociated) parameters"
+                   << std::endl;
+         multiPdfParams.Print("V");
+      }
+      setAllConstant(multiPdfParams, freeze);
+
+      // std::cout << " Current state of all MultiPdfParams -> " << std::endl;
+      // std::unique_ptr<TIterator> iter_par(allRooMultiPdfParams.createIterator());
+      // for (RooAbsArg *P = (RooAbsArg *) iter_par->Next(); P != 0; P = (RooAbsArg *) iter_par->Next()){
+      //   std::cout << P->GetName() << ", constant=" << P->isConstant() << std::endl;
+      // }
+      return true;
+   }
+
+   return false;
+}
+
 } // namespace RooHelpers

roofit/roostats/inc/RooStats/RooStatsUtils.h

@@ -65,19 +65,11 @@ namespace RooStats {
    }
 
    inline void RemoveConstantParameters(RooArgSet* set){
-      RooArgSet constSet;
-      for (auto const *myarg : static_range_cast<RooRealVar *>(*set)) {
-         if(myarg->isConstant()) constSet.add(*myarg);
-      }
-      set->remove(constSet);
+      set->removeConstantParameters();
    }
 
    inline void RemoveConstantParameters(RooArgList& set){
-      RooArgSet constSet;
-      for (auto const *myarg : static_range_cast<RooRealVar *>(set)) {
-         if(myarg->isConstant()) constSet.add(*myarg);
-      }
-      set.remove(constSet);
+      set.removeConstantParameters();
    }
 
    /// utility function to set all variable constant in a collection