ServiceRegistry/interface/RandomEngineSentry.h

0001 #ifndef FWCore_ServiceRegistry_RandomEngineSentry_h
0002 #define FWCore_ServiceRegistry_RandomEngineSentry_h
0003
0004 /**\class edm::RandomEngineSentry
0005
0006 Description:
0007
0008 */
0009 //
0010 // Original Author: W. David Dagenhart
0011 //         Created: 11/26/2013
0012
0013 #include "FWCore/ServiceRegistry/interface/Service.h"
0014 #include "FWCore/Utilities/interface/Exception.h"
0015 #include "FWCore/Utilities/interface/RandomNumberGenerator.h"
0016 #include "FWCore/Utilities/interface/get_underlying_safe.h"
0017
0018 namespace CLHEP {
0019   class HepRandomEngine;
0020 }
0021
0022 namespace edm {
0023
0024   class LuminosityBlockIndex;
0025   class StreamID;
0026
0027   template <class T>
0028   class RandomEngineSentry {
0029   public:
0030     explicit RandomEngineSentry(T* t, CLHEP::HepRandomEngine* engine) : t_(t), engine_(engine) {
0031       if (t) {
0032         t->setRandomEngine(engine);
0033       }
0034     }
0035
0036     explicit RandomEngineSentry(T* t, StreamID const& streamID) : t_(t), engine_(nullptr) {
0037       if (t) {
0038         Service<RandomNumberGenerator> rng;
0039         if (!rng.isAvailable()) {
0040           throw cms::Exception("Configuration")
0041               << "Attempt to get a random engine when the RandomNumberGeneratorService is not configured.\n"
0042                  "You must configure the service if you want an engine.\n";
0043         }
0044         engine_ = &rng->getEngine(streamID);
0045         t->setRandomEngine(engine_);
0046       }
0047     }
0048
0049     explicit RandomEngineSentry(T* t, LuminosityBlockIndex const& lumi) : t_(t), engine_(nullptr) {
0050       if (t) {
0051         Service<RandomNumberGenerator> rng;
0052         if (!rng.isAvailable()) {
0053           throw cms::Exception("Configuration")
0054               << "Attempt to get a random engine when the RandomNumberGeneratorService is not configured.\n"
0055                  "You must configure the service if you want an engine.\n";
0056         }
0057         engine_ = &rng->getEngine(lumi);
0058         t->setRandomEngine(engine_);
0059       }
0060     }
0061
0062     ~RandomEngineSentry() {
0063       if (t_)
0064         t_->setRandomEngine(nullptr);
0065     }
0066
0067     CLHEP::HepRandomEngine const* randomEngine() const { return get_underlying_safe(engine_); }
0068     CLHEP::HepRandomEngine*& randomEngine() { return get_underlying_safe(engine_); }
0069
0070   private:
0071     edm::propagate_const<T*> t_;
0072     edm::propagate_const<CLHEP::HepRandomEngine*> engine_;
0073   };
0074 }  // namespace edm
0075 #endif