Fill histograms in parallel and write them on file. This example expresses the parallelism of the mt001_fillHistos.C tutorial with multiprocessing techniques.
Author: Danilo Piparo
This notebook tutorial was automatically generated with ROOTBOOK-izer from the macro found in the ROOT repository on Wednesday, April 17, 2024 at 11:15 AM.
const UInt_t nNumbers = 20000000U;
const UInt_t nWorkers = 4U;
We define our work item
auto workItem = [](UInt_t workerID) {
// One generator, file and ntuple per worker
TRandom3 workerRndm(workerID); // Change the seed
TFile f(Form("myFile_mp001_%u.root", workerID), "RECREATE");
TH1F h(Form("myHisto_%u", workerID), "The Histogram", 64, -4, 4);
for (UInt_t i = 0; i < nNumbers; ++i) {
h.Fill(workerRndm.Gaus());
}
h.Write();
return 0;
};
Create the pool of workers
ROOT::TProcessExecutor workers(nWorkers);
Fill the pool with work
workers.Map(workItem, ROOT::TSeqI(nWorkers));
return 0;