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Reference Guide
mp201_parallelHistoFill.C File Reference

Detailed Description

View in nbviewer Open in SWAN Parallel fill of a histogram This tutorial shows how a histogram can be filled in parallel with a multiprocess approach.

const UInt_t poolSize = 4U;
Int_t mp201_parallelHistoFill()
ROOT::TProcessExecutor pool(poolSize);
auto fillRandomHisto = [](int seed = 0) {
TRandom3 rndm(seed);
auto h = new TH1F("myHist", "Filled in parallel", 128, -8, 8);
for (auto i : ROOT::TSeqI(1000000)) {
h->Fill(rndm.Gaus(0, 1));
return h;
auto seeds = ROOT::TSeqI(23);
auto sumRandomHisto = pool.MapReduce(fillRandomHisto, seeds, redfunc);
auto c = new TCanvas();
return 0;
#define c(i)
Definition: RSha256.hxx:101
#define h(i)
Definition: RSha256.hxx:106
int Int_t
Definition: RtypesCore.h:45
unsigned int UInt_t
Definition: RtypesCore.h:46
Merge collection of TObjects.
Definition: PoolUtils.h:35
This class provides a simple interface to execute the same task multiple times in parallel,...
A pseudo container class which is a generator of indices.
Definition: TSeq.hxx:66
The Canvas class.
Definition: TCanvas.h:23
1-D histogram with a float per channel (see TH1 documentation)}
Definition: TH1.h:575
static void AddDirectory(Bool_t add=kTRUE)
Sets the flag controlling the automatic add of histograms in memory.
Definition: TH1.cxx:1282
Random number generator class based on M.
Definition: TRandom3.h:27
TSeq< int > TSeqI
Definition: TSeq.hxx:194
January 2016
Danilo Piparo

Definition in file mp201_parallelHistoFill.C.