{
 "cells": [
  {
   "cell_type": "markdown",
   "id": "a700ea2a",
   "metadata": {},
   "source": [
    "# mp_processSelector\n",
    "Illustrate the usage of the multiprocessing TTreeProcessorMP\n",
    "and TSelector interfaces with the h1analysis.C example.\n",
    "\n",
    "\n",
    "\n",
    "\n",
    "**Author:**  Anda Chelba, Gerardo Ganis  \n",
    "<i><small>This notebook tutorial was automatically generated with <a href= \"https://github.com/root-project/root/blob/master/documentation/doxygen/converttonotebook.py\">ROOTBOOK-izer</a> from the macro found in the ROOT repository  on Tuesday, May 19, 2026 at 08:11 PM.</small></i>"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "3130e344",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "%%cpp -d\n",
    "\n",
    "#include \"TString.h\"\n",
    "#include \"TROOT.h\"\n",
    "#include \"TChain.h\"\n",
    "#include \"TBranch.h\"\n",
    "#include \"TFileCollection.h\"\n",
    "#include \"TH1F.h\"\n",
    "#include \"TTreeReader.h\"\n",
    "#include \"ROOT/TTreeProcessorMP.hxx\"\n",
    "\n",
    "#include <memory>\n",
    "\n",
    "const auto file0 = \"root://eospublic.cern.ch//eos/root-eos/h1/dstarmb.root\";\n",
    "const std::vector<std::string> files = {file0,\n",
    "                                        \"root://eospublic.cern.ch//eos/root-eos/h1/dstarp1a.root\",\n",
    "                                        \"root://eospublic.cern.ch//eos/root-eos/h1/dstarp1b.root\",\n",
    "                                        \"root://eospublic.cern.ch//eos/root-eos/h1/dstarp2.root\"};"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "ff3e0888",
   "metadata": {},
   "source": [
    "MacOSX may generate connection to WindowServer errors"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "d6379828",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "gROOT->SetBatch(kTRUE);\n",
    "\n",
    "TString selectorPath = gROOT->GetTutorialDir();\n",
    "selectorPath += \"/analysis/tree/h1analysis.C+\";\n",
    "std::cout << \"selector used is: \" << selectorPath << \"\\n\";\n",
    "auto sel = TSelector::GetSelector(selectorPath);"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "8307add1",
   "metadata": {},
   "source": [
    "The following code generates a crash when Davix is used for HTTP\n",
    "Davix does not seem fork-safe; the problem has been reported to the\n",
    "Davix developers. For the time being we disable this part.\n",
    "To repoduce the problem, uncomment the next line.\n",
    "\n",
    "#define __reproduce_davix"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "f98fa495",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "#if defined(__reproduce_davix)\n",
    "auto fp = std::make_unique<TTree>(TFile::Open(file0));\n",
    "auto tree = fp->Get<TTree>(\"h42\");\n",
    "#endif\n",
    "\n",
    "ROOT::TTreeProcessorMP pool(3);\n",
    "\n",
    "TList *out = nullptr;\n",
    "#if defined(__reproduce_davix)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "252dd1fc",
   "metadata": {},
   "source": [
    "TTreeProcessorMP::Process with a single tree"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "8d681828",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "out = pool.Process(*tree, *sel);\n",
    "sel->GetOutputList()->Delete();\n",
    "#endif"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "ff7b22cb",
   "metadata": {},
   "source": [
    "TTreeProcessorMP::Process with single file name and tree name\n",
    "Note: we have less files than workers here"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "957068cc",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "out = pool.Process(file0, *sel, \"h42\");\n",
    "sel->GetOutputList()->Delete();"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "2f24bb20",
   "metadata": {},
   "source": [
    "Prepare datasets: vector of files, TFileCollection"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "cb6d2803",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "TChain ch;\n",
    "TFileCollection fc;\n",
    "for (auto &&file : files) {\n",
    "   fc.Add(new TFileInfo(file.c_str()));\n",
    "   ch.Add(file.c_str());\n",
    "}"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "3f78da54",
   "metadata": {},
   "source": [
    "TTreeProcessorMP::Process with vector of files and tree name\n",
    "Note: we have more files than workers here (different behaviour)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "5b9ac6aa",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "out = pool.Process(files, *sel, \"h42\");\n",
    "sel->GetOutputList()->Delete();"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "3937e82b",
   "metadata": {},
   "source": [
    "TTreeProcessorMP::Process with TFileCollection, no tree name"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "28315597",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "out = pool.Process(fc, *sel);\n",
    "sel->GetOutputList()->Delete();"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "4c22fd34",
   "metadata": {},
   "source": [
    "TTreeProcessorMP::Process with TChain, no tree name"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "f95d785d",
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "out = pool.Process(ch, *sel);\n",
    "sel->GetOutputList()->Delete();\n",
    "\n",
    "return 0;"
   ]
  }
 ],
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