From 709053b258ba03c365ff5cf3117daa42aa8d9bee Mon Sep 17 00:00:00 2001
From: richterm <richterm@f7af4fe6-9843-0410-8265-dc069ae4e863>
Date: Wed, 14 Sep 2011 14:22:10 +0000
Subject: [PATCH] calculating entropy for parameter histograms

---
 HLT/BASE/AliHLTDataDeflaterSimple.cxx | 34 +++++++++++++++++++++++++++
 HLT/BASE/AliHLTDataDeflaterSimple.h   |  2 ++
 2 files changed, 36 insertions(+)

diff --git a/HLT/BASE/AliHLTDataDeflaterSimple.cxx b/HLT/BASE/AliHLTDataDeflaterSimple.cxx
index c684271085c..bc96e7ff330 100644
--- a/HLT/BASE/AliHLTDataDeflaterSimple.cxx
+++ b/HLT/BASE/AliHLTDataDeflaterSimple.cxx
@@ -28,6 +28,7 @@
 #include "TObjArray.h"
 #include "TH1I.h"
 #include "TH2F.h"
+#include "TMath.h"
 #include <memory>
 #include <algorithm>
 #include <iostream>
@@ -163,12 +164,45 @@ void AliHLTDataDeflaterSimple::SaveAs(const char *filename,Option_t */*option*/)
   }
   file->cd();
   if (fHistograms) {
+    for (int i=0; i<fHistograms->GetEntries(); i++) {
+      if (fHistograms->At(i)==NULL || 
+	  !fHistograms->At(i)->InheritsFrom("TH1") ||
+	  fHistograms->At(i)->InheritsFrom("TH2") ||
+	  fHistograms->At(i)->InheritsFrom("TH3")
+	  ) continue;
+      TH1* h=reinterpret_cast<TH1*>(fHistograms->At(i));
+      if (!h) continue;
+      float entropy=CalcEntropy(h);
+      if (entropy<0) continue;
+      TString title=h->GetTitle();
+      title+=Form(" entropy %.2f", entropy);
+      h->SetTitle(title);
+    }
     fHistograms->Write();
   }
 
   file->Close();
 }
 
+float AliHLTDataDeflaterSimple::CalcEntropy(TH1* histo, const char* /*option*/, int mode)
+{
+
+  if (!histo) return -1000.;
+
+  float l2=TMath::Log(2.0);
+  float integral=histo->Integral(0,histo->GetNbinsX());
+  int centerbin=mode*histo->GetNbinsX()/2;
+  int nofBins=histo->GetNbinsX()-centerbin;
+  float entropy=0.0;
+  for (int offset=0; offset<nofBins; offset++) {
+    float abundance=histo->GetBinContent(offset);
+    if (abundance<1.0) continue;
+    entropy += (- (Double_t) abundance / (Double_t) integral ) * log( ( (Double_t) abundance / (Double_t) integral )) / (l2);
+  }
+
+  return entropy;
+}
+
 void AliHLTDataDeflaterSimple::Print(Option_t *option) const
 {
   // print info
diff --git a/HLT/BASE/AliHLTDataDeflaterSimple.h b/HLT/BASE/AliHLTDataDeflaterSimple.h
index eeea64762ea..3fd9bbdc09a 100644
--- a/HLT/BASE/AliHLTDataDeflaterSimple.h
+++ b/HLT/BASE/AliHLTDataDeflaterSimple.h
@@ -131,6 +131,8 @@ public:
   /// DataDeflaterSimple has deflater version 1
   virtual int GetDeflaterVersion() const {return 1;}
 
+  static float CalcEntropy(TH1* histo, const char* option="", int mode=0);
+
  protected:
  private:
   /// copy constructor prohibited
-- 
2.43.0