Fill n-tuples in distinct workers.
This tutorial illustrates the basics of how it's possible with ROOT to offload heavy operations on multiple processes and how it's possible to write simultaneously multiple files. The operation performed in this case is the creation of random gaussian numbers.
const UInt_t nNumbers = 20000000U;
const auto workSize = nNumbers / nThreads;
{
for (
auto i :
ROOT::TSeqI(
n))
ntuple.Fill(rndm.Gaus());
}
Int_t mtbb101_fillNtuples()
{
TFile ofile(
"mtbb101_singleCore.root",
"RECREATE");
TNtuple randomNumbers(
"singleCore",
"Random Numbers",
"r");
fillRandom(randomNumbers, rndm, nNumbers);
randomNumbers.Write();
ofile.Close();
auto workItem = [](
UInt_t workerID) {
TFile ofile(
Form(
"mtbb101_multiCore_%u.root", workerID),
"RECREATE");
TNtuple workerRandomNumbers(
"multiCore",
"Random Numbers",
"r");
fillRandom(workerRandomNumbers, workerRndm, workSize);
workerRandomNumbers.Write();
return 0;
};
return 0;
}
char * Form(const char *fmt,...)
Formats a string in a circular formatting buffer.
A pseudo container class which is a generator of indices.
This class provides a simple interface to execute the same task multiple times in parallel threads,...
A ROOT file is composed of a header, followed by consecutive data records (TKey instances) with a wel...
A simple TTree restricted to a list of float variables only.
Random number generator class based on M.
This file contains a specialised ROOT message handler to test for diagnostic in unit tests.
- Date
- January 2016
- Author
- Danilo Piparo
Definition in file mtbb101_fillNtuples.C.