refactor seed setting for simulation

now also works in serial app

Author: sawenzel

Common/Utils/CMakeLists.txt

@@ -16,6 +16,7 @@ Set(HEADERS
   include/${MODULE_NAME}/RootChain.h
   include/${MODULE_NAME}/BoostSerializer.h
   include/${MODULE_NAME}/ShmManager.h
+  include/${MODULE_NAME}/RngHelper.h
 )
 
 Set(LINKDEF src/CommonUtilsLinkDef.h)

Common/Utils/include/CommonUtils/RngHelper.h

@@ -0,0 +1,66 @@
+// Copyright CERN and copyright holders of ALICE O2. This software is
+// distributed under the terms of the GNU General Public License v3 (GPL
+// Version 3), copied verbatim in the file "COPYING".
+//
+// See http://alice-o2.web.cern.ch/license for full licensing information.
+//
+// In applying this license CERN does not waive the privileges and immunities
+// granted to it by virtue of its status as an Intergovernmental Organization
+// or submit itself to any jurisdiction.
+
+/*
+ * RngHelper.h
+ *
+ *  Created on: Jun 18, 2018
+ *      Author: swenzel
+ */
+
+#ifndef COMMON_UTILS_INCLUDE_COMMONUTILS_RNGHELPER_H_
+#define COMMON_UTILS_INCLUDE_COMMONUTILS_RNGHELPER_H_
+
+#include <TRandom.h>
+#include <fcntl.h>
+
+namespace o2
+{
+namespace utils
+{
+
+// helper functions for random number (management)
+class RngHelper
+{
+ public:
+  // sets the state of the currently active ROOT gRandom Instance
+  // if -1 (or negative) is given ... we will init with a random seed
+  // returns seed set to TRandom
+  static unsigned int setGRandomSeed(int seed = -1)
+  {
+    unsigned int s = seed < 0 ? readURandom<unsigned int>() : seed;
+    gRandom->SetSeed(s);
+    return s;
+  }
+
+  // static function to get a true random number from /dev/urandom
+  template <typename T>
+  static T readURandom()
+  {
+    int randomDataHandle = open("/dev/urandom", O_RDONLY);
+    if (randomDataHandle < 0) {
+      // something went wrong
+    } else {
+      T seed;
+      auto result = read(randomDataHandle, &seed, sizeof(T));
+      if (result < 0) {
+        // something went wrong
+      }
+      close(randomDataHandle);
+      return seed;
+    }
+    return T(0);
+  }
+};
+
+} // namespace utils
+} // namespace o2
+
+#endif /* COMMON_UTILS_INCLUDE_COMMONUTILS_RNGHELPER_H_ */

Common/Utils/src/CommonUtilsLinkDef.h

@@ -18,5 +18,6 @@
 #pragma link C++ class o2::utils::TreeStream+;
 #pragma link C++ class o2::utils::TreeStreamRedirector+;
 #pragma link C++ class o2::utils::RootChain + ;
+#pragma link C++ class o2::utils::RngHelper;
 
 #endif

macro/o2sim.C

@@ -15,6 +15,7 @@
 #include <Generators/PDG.h>
 #include <SimConfig/SimConfig.h>
 #include <SimConfig/ConfigurableParam.h>
+#include <CommonUtils/RngHelper.h>
 #include <TStopwatch.h>
 #include <memory>
 #include "DataFormatsParameters/GRPObject.h"
@@ -40,8 +41,11 @@ FairRunSim* o2sim_init(bool asservice)
   // we can update the binary CCDB entry something like this ( + timestamp key )
   // o2::conf::ConfigurableParam::toCCDB("params_ccdb.root");
 
-  auto genconfig = confref.getGenerator();
+  // set seed
+  auto seed = o2::utils::RngHelper::setGRandomSeed(confref.getStartSeed());
+  LOG(INFO) << "RNG INITIAL SEED " << seed;
 
+  auto genconfig = confref.getGenerator();
   FairRunSim* run;
   if (asservice) {
     run = new o2::steer::O2RunSim();

run/O2PrimaryServerDevice.h

@@ -24,10 +24,10 @@
 #include <SimulationDataFormat/PrimaryChunk.h>
 #include <Generators/GeneratorFromFile.h>
 #include <SimConfig/SimConfig.h>
+#include <CommonUtils/RngHelper.h>
 #include <typeinfo>
 #include <thread>
 #include <TROOT.h>
-#include <fcntl.h>
 
 namespace o2
 {
@@ -76,12 +76,8 @@ class O2PrimaryServerDevice : public FairMQDevice
 
     // 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);
+    mInitialSeed = o2::utils::RngHelper::setGRandomSeed(mInitialSeed);
+    LOG(INFO) << "RNG INITIAL SEED " << mInitialSeed;
 
     mMaxEvents = conf.getNEvents();
 
@@ -211,24 +207,6 @@ 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;