Possibility to set seed for simulation

Allow to set the seed for simulation. By default
a random seed will be chosen at each start. If reproducible tests
are needed ... set the seed with the --seed option.

For the moment, change restricted to o2sim_parallel.

Author: sawenzel

Common/SimConfig/include/SimConfig/SimConfig.h

@@ -39,8 +39,10 @@ struct SimConfigData {
                                              // (can be used to **loosly** change any configuration parameter from
                                              //  command-line)
   int mPrimaryChunkSize;                     // defining max granularity for input primaries of a sim job
-  int mInternalChunkSize;
-  ClassDefNV(SimConfigData, 1);
+  int mInternalChunkSize;                    //
+  int mStartSeed;                            // base for random number seeds
+
+  ClassDefNV(SimConfigData, 2);
 };
 
 // A singleton class which can be used
@@ -97,6 +99,7 @@ class SimConfig
   std::string getKeyValueString() const { return mConfigData.mKeyValueTokens; }
   int getPrimChunkSize() const { return mConfigData.mPrimaryChunkSize; }
   int getInternalChunkSize() const { return mConfigData.mInternalChunkSize; }
+  int getStartSeed() const { return mConfigData.mStartSeed; }
 
  private:
   SimConfigData mConfigData; //!

Common/SimConfig/src/SimConfig.cxx

@@ -36,7 +36,9 @@ void SimConfig::initOptions(boost::program_options::options_description& options
     "outPrefix,o", bpo::value<std::string>()->default_value("o2sim"), "prefix of output files")(
     "logseverity", bpo::value<std::string>()->default_value("INFO"), "severity level for FairLogger")(
     "logverbosity", bpo::value<std::string>()->default_value("low"), "level of verbosity for FairLogger (low, medium, high, veryhigh)")(
-    "configKeyValues", bpo::value<std::string>()->default_value(""), "comma separated key=value strings (e.g.: 'TPC.gasDensity=1,...")("chunkSize", bpo::value<unsigned int>()->default_value(10000), "max size of primary chunk (subevent) distributed by server")("chunkSizeI", bpo::value<int>()->default_value(-1), "internalChunkSize");
+    "configKeyValues", bpo::value<std::string>()->default_value(""), "comma separated key=value strings (e.g.: 'TPC.gasDensity=1,...")("chunkSize", bpo::value<unsigned int>()->default_value(10000), "max size of primary chunk (subevent) distributed by server")(
+    "chunkSizeI", bpo::value<int>()->default_value(-1), "internalChunkSize")(
+    "seed", bpo::value<int>()->default_value(-1), "initial seed (default: -1 random)");
 }
 
 bool SimConfig::resetFromParsedMap(boost::program_options::variables_map const& vm)
@@ -82,6 +84,7 @@ bool SimConfig::resetFromParsedMap(boost::program_options::variables_map const&
   mConfigData.mKeyValueTokens = vm["configKeyValues"].as<std::string>();
   mConfigData.mPrimaryChunkSize = vm["chunkSize"].as<unsigned int>();
   mConfigData.mInternalChunkSize = vm["chunkSizeI"].as<int>();
+  mConfigData.mStartSeed = vm["seed"].as<int>();
   return true;
 }
 

run/O2PrimaryServerDevice.h

@@ -27,6 +27,7 @@
 #include <typeinfo>
 #include <thread>
 #include <TROOT.h>
+#include <fcntl.h>
 
 namespace o2
 {
@@ -73,6 +74,15 @@ class O2PrimaryServerDevice : public FairMQDevice
     mChunkGranularity = vm["chunkSize"].as<unsigned int>();
     LOG(INFO) << "CHUNK SIZE SET TO " << mChunkGranularity;
 
+    // initial initial seed --> we should store this somewhere
+    mInitialSeed = vm["seed"].as<int>();
+    if (mInitialSeed == -1) {
+      mInitialSeed = getRandomSeed();
+    }
+    LOG(INFO) << "INITIAL SEED " << mInitialSeed;
+    // set seed here ... in order to influence already event generation
+    gRandom->SetSeed(mInitialSeed);
+
     mMaxEvents = conf.getNEvents();
 
     // need to make ROOT thread-safe since we use ROOT services in all places
@@ -151,7 +161,7 @@ class O2PrimaryServerDevice : public FairMQDevice
     i.maxEvents = mMaxEvents;
     i.part = mPartCounter + 1;
     i.nparts = numberofparts;
-    i.seed = counter + 10;
+    i.seed = counter + mInitialSeed;
     i.index = m.mParticles.size();
     m.mEventIDs.emplace_back(i);
 
@@ -201,6 +211,24 @@ class O2PrimaryServerDevice : public FairMQDevice
   }
 
  private:
+  // helper function to get truly random seed
+  int getRandomSeed() const
+  {
+    int randomDataHandle = open("/dev/urandom", O_RDONLY);
+    if (randomDataHandle < 0) {
+      // something went wrong
+    } else {
+      int seed;
+      auto result = read(randomDataHandle, &seed, sizeof(seed));
+      if (result < 0) {
+        // something went wrong
+      }
+      close(randomDataHandle);
+      return seed;
+    }
+    return 0;
+  }
+
   std::string mOutChannelName = "";
   FairPrimaryGenerator mPrimGen;
   FairMCEventHeader mEventHeader;
@@ -210,6 +238,7 @@ class O2PrimaryServerDevice : public FairMQDevice
   int mPartCounter = 0;
   bool mNeedNewEvent = true;
   int mMaxEvents = 2;
+  int mInitialSeed = -1;
 
   std::thread mGeneratorInitThread; //! a thread used to concurrently init the particle generator
 };