Allow to specify the starting orbit as a fractional value

Allow to provide the start orbit as a fraction (e.g, 32.7).
This will determine the starting bunch crossing relative
to the integral orbit part.

In result, this allows to construct collisions starting somewhere within
an orbit ... not only at the start.

Author: sawenzel

Steer/src/CollisionContextTool.cxx

@@ -45,7 +45,9 @@ struct Options {
   bool printContext = false;
   std::string bcpatternfile;
   int tfid = 0;          // tfid -> used to calculate start orbit for collisions
+  double firstFractionalOrbit; // capture orbit and bunch crossing via decimal number
   uint32_t firstOrbit = 0; // first orbit in run (orbit offset)
+  uint32_t firstBC = 0;    // first bunch crossing (relative to firstOrbit) of the first interaction;
   int orbitsPerTF = 256; // number of orbits per timeframe --> used to calculate start orbit for collisions
   bool useexistingkinematics = false;
   bool noEmptyTF = false; // prevent empty timeframes; the first interaction will be shifted backwards to fall within the range given by Options.orbits
@@ -196,7 +198,7 @@ bool parseOptions(int argc, char* argv[], Options& optvalues)
     "orbitsPerTF", bpo::value<int>(&optvalues.orbitsPerTF)->default_value(256), "Orbits per timeframes")(
     "use-existing-kine", "Read existing kinematics to adjust event counts")(
     "timeframeID", bpo::value<int>(&optvalues.tfid)->default_value(0), "Timeframe id of the first timeframe int this context. Allows to generate contexts for different start orbits")(
-    "first-orbit", bpo::value<uint32_t>(&optvalues.firstOrbit)->default_value(0), "First orbit in the run (HBFUtils.firstOrbit)")(
+    "first-orbit", bpo::value<double>(&optvalues.firstFractionalOrbit)->default_value(0), "First (fractional) orbit in the run (HBFUtils.firstOrbit + BC from decimal)")(
     "maxCollsPerTF", bpo::value<int>(&optvalues.maxCollsPerTF)->default_value(-1), "Maximal number of MC collisions to put into one timeframe. By default no constraint.")(
     "noEmptyTF", bpo::bool_switch(&optvalues.noEmptyTF), "Enforce to have at least one collision")("configKeyValues", bpo::value<std::string>(&optvalues.configKeyValues)->default_value(""), "Semicolon separated key=value strings (e.g.: 'TPC.gasDensity=1;...')")("with-vertices", "Assign vertices to collisions.")("timestamp", bpo::value<long>(&optvalues.timestamp)->default_value(-1L), "Timestamp for CCDB queries / anchoring");
 
@@ -221,6 +223,14 @@ bool parseOptions(int argc, char* argv[], Options& optvalues)
     if (vm.count("with-vertices")) {
       optvalues.genVertices = true;
     }
+
+    // fix the first orbit and bunch crossing
+    // auto orbitbcpair = parseOrbitAndBC(optvalues.firstIRString);
+    optvalues.firstOrbit = (uint32_t)optvalues.firstFractionalOrbit;
+    optvalues.firstBC = (uint32_t)((optvalues.firstFractionalOrbit - 1. * optvalues.firstOrbit) * o2::constants::lhc::LHCMaxBunches);
+    LOG(info) << "First orbit " << optvalues.firstOrbit;
+    LOG(info) << "First BC " << optvalues.firstBC;
+
   } catch (const bpo::error& e) {
     std::cerr << e.what() << "\n\n";
     std::cerr << "Error parsing options; Available options:\n";
@@ -285,7 +295,7 @@ int main(int argc, char* argv[])
       o2::InteractionTimeRecord record;
       // this loop makes sure that the first collision is within the range of orbits asked (if noEmptyTF is enabled)
       do {
-        sampler.setFirstIR(o2::InteractionRecord(0, orbitstart));
+        sampler.setFirstIR(o2::InteractionRecord(options.firstBC, orbitstart));
         sampler.init();
         record = sampler.generateCollisionTime();
       } while (options.noEmptyTF && usetimeframelength && record.orbit >= orbitstart + options.orbits);