tutorials/multicore: two new tutorials to illustrate autobin in power-of-2 mode

tutorials/multicore/mt304_fillHistos.C

+/// \file
+/// \ingroup tutorial_multicore
+/// Fill histograms in parallel with automatic binning.
+/// Illustrates use of power-of-two autobin algorithm
+///
+/// \macro_code
+///
+/// \author Gerardo Ganis
+/// \date November 2017
+#include "TH1D.h"
+#include "TH2D.h"
+#include "TH3D.h"
+#include "TList.h"
+#include "TRandom3.h"
+#include "TDirectory.h"
+#include "TROOT.h"
+#include "TCanvas.h"
+#include "TString.h"
+#include "TStyle.h"
+#include "ROOT/TSeq.hxx"
+#include "ROOT/TThreadedObject.hxx"
+
+#include <thread>
+#include <iostream>
+
+
+// The number of workers
+const UInt_t nWorkers = 8U;
+
+// Reference boundaries
+const Double_t xmiref = -1.;
+const Double_t xmaref =  7.;
+
+Int_t mt304_fillHistos(UInt_t nNumbers = 1001)
+{
+
+   // The first, fundamental operation to be performed in order to make ROOT
+   // thread-aware.
+   ROOT::EnableThreadSafety();
+
+   // Histograms to be filled in parallel
+   ROOT::TThreadedObject<TH1D> h1d("h1d", "1D test histogram", 64, 0., -1.);
+   ROOT::TThreadedObject<TH1D> h1dr("h1dr", "1D test histogram w/ ref boundaries", 64, xmiref, xmaref);
+
+   // We define our work item
+   auto workItem = [&](UInt_t workerID) {
+      // One generator, file and ntuple per worker
+      TRandom3 workerRndm(workerID); // Change the seed
+
+      auto wh1d = h1d.Get();
+      wh1d->SetBit(TH1::kAutoBinPTwo);
+      auto wh1dr = h1dr.Get();
+
+      Double_t x;
+      for (UInt_t i = 0; i < nNumbers; ++i) {
+         x = workerRndm.Gaus(3.);
+         wh1d->Fill(x);
+         wh1dr->Fill(x);
+      }
+   };
+
+   // Create the collection which will hold the threads, our "pool"
+   std::vector<std::thread> workers;
+
+   // Fill the "pool" with workers
+   for (auto workerID : ROOT::TSeqI(nWorkers)) {
+      workers.emplace_back(workItem, workerID);
+   }
+
+   // Now join them
+   for (auto && worker : workers) worker.join();
+
+   // Merge
+   auto fh1d = h1d.Merge();
+   auto fh1dr = h1dr.Merge();
+
+   // Make the canvas
+   TCanvas *c = new TCanvas("c", "c", 800, 800);
+   c->Divide(1,2);
+
+   gStyle->SetOptStat(111110);
+   c->cd(1);
+   fh1d->DrawCopy();
+   c->cd(2);
+   fh1dr->DrawCopy();
+
+   c->Update();
+
+   gROOTMutex = 0;
+
+   return 0;
+}

tutorials/multicore/mt305_fillHistosAutobin.C

+/// \file
+/// \ingroup tutorial_multicore
+/// Fill multiple histograms with different functions and automatic binning.
+/// Illustrates merging with the power-of-two autobin algorithm
+///
+/// \macro_code
+///
+/// \author Gerardo Ganis
+/// \date November 2017
+#include "TF1.h"
+#include "TH1D.h"
+#include "TMath.h"
+#include "TF1.h"
+#include "TCanvas.h"
+#include "TRandom3.h"
+#include "TStatistic.h"
+#include "TFile.h"
+#include "TStyle.h"
+
+TF1 *gam = new TF1("gam", "1/(1+0.1*x*0.1*x)", -100., 100.);
+TF1 *gam1 = new TF1("gam", "1/(1+0.1*x*0.1*x)", -1., .25);
+TF1 *iga = new TF1("inv gam", "1.-1/(1+0.1*x*0.1*x)", -100., 100.);
+TF1 *iga1 = new TF1("inv gam", "1.-1/(1+0.1*x*0.1*x)", -.5, 1.);
+
+void mt305_fillHistosAutobin(unsigned opt = 1, unsigned n = 1001)
+{
+
+   UInt_t nh = 10;
+   UInt_t bsize = 1000;
+
+   TRandom3 rndm((Long64_t)time(0));
+
+   // Standard autobinning reference
+   auto href = new TH1D("myhref", "current", 50, 0., -1.);
+   href->SetBuffer(bsize);
+
+   // New autobinning 1-histo reference
+   auto href2 = new TH1D("myhref", "Auto P2, sequential", 50, 0., -1.);
+   href2->SetBit(TH1::kAutoBinPTwo);
+   href2->SetBuffer(bsize);
+
+   TList *hlist = new TList;
+
+   Int_t nbins = 50;
+
+   TStatistic x("min"), y("max"), d("dif"), a("mean"), r("rms");
+   for (UInt_t j = 0; j < nh; ++j) {
+      Double_t xmi = 1e15, xma = -1e15;
+      TStatistic xw("work");
+      TString hname = TString::Format("myh%d", j);
+      auto hw = new TH1D(hname.Data(), "Auto P2, merged", nbins, 0., -1.);
+      hw->SetBit(TH1::kAutoBinPTwo);
+      hw->SetBuffer(bsize);
+
+      Double_t xhma, xhmi, ovf, unf;
+      Bool_t emptied = kFALSE, tofill = kTRUE;
+      Bool_t buffering = kTRUE;
+      for (UInt_t i = 0; i < n; ++i) {
+
+         Double_t xx;
+         switch (opt) {
+         case 1: xx = rndm.Gaus(3, 1); break;
+         case 2: xx = rndm.Rndm() * 100. - 50.; break;
+         case 3: xx = gam->GetRandom(); break;
+         case 4: xx = gam1->GetRandom(); break;
+         case 5: xx = iga->GetRandom(); break;
+         case 6: xx = iga1->GetRandom(); break;
+         default: xx = rndm.Gaus(0, 1);
+         }
+
+         if (buffering) {
+            if (xx > xma)
+               xma = xx;
+            if (xx < xmi)
+               xmi = xx;
+            xw.Fill(xx);
+         }
+         hw->Fill(xx);
+         href->Fill(xx);
+         href2->Fill(xx);
+         if (!hw->GetBuffer()) {
+            // Not buffering anymore
+            buffering = kFALSE;
+         }
+      }
+      x.Fill(xmi);
+      y.Fill(xma);
+      d.Fill(xma - xmi);
+      a.Fill(xw.GetMean());
+      r.Fill(xw.GetRMS());
+
+      hlist->Add(hw);
+   }
+
+   x.Print();
+   y.Print();
+   d.Print();
+   a.Print();
+   r.Print();
+
+   TH1D *h0 = (TH1D *)hlist->First();
+   hlist->Remove(h0);
+   if (!h0->Merge(hlist))
+      return;
+
+   gStyle->SetOptStat(111110);
+
+   if (gROOT->GetListOfCanvases()->FindObject("c3"))
+      delete gROOT->GetListOfCanvases()->FindObject("c3");
+   TCanvas *c3 = new TCanvas("c3", "c3", 800, 800);
+   c3->Divide(1, 3);
+   c3->cd(1);
+   h0->StatOverflows();
+   h0->DrawClone("HIST");
+
+   c3->cd(2);
+   href2->StatOverflows();
+   href2->DrawClone();
+
+   c3->cd(3);
+   href->StatOverflows();
+   href->DrawClone();
+   c3->Update();
+   std::cout << " ent: " << h0->GetEntries() << "\n";
+   h0->Print();
+   href->Print();
+
+   hlist->SetOwner(kTRUE);
+   delete hlist;
+   delete href;
+   delete href2;
+   delete h0;
+}