Utilities for particle gun and MC truth

Can now generate multiple particles per event, each sampled independently from the specified single particle momentum/position/PID ranges.

Also added a simple example algorithm to dump each event's truth record.

Control/CalypsoExample/TruthEventDumper/python/TruthEventDumperAlg.py

+# Copyright (C) 2002-2021 CERN for the benefit of the ATLAS collaboration
+
+import AthenaPython.PyAthena as PyAthena
+from AthenaPython.PyAthena import StatusCode, McEventCollection, HepMC, CLHEP
+import McParticleEvent.Pythonizations
+
+__author__ = "Dave Caser <dcasper@uci.edu>"
+
+class TruthEventDumperAlg(PyAthena.Alg):
+    def __init__(self, name="TruthEventDumper", MCEventKey="TruthEvent"):
+        super(TruthEventDumperAlg,self).__init__(name=name)
+        self.MCEventKey = MCEventKey
+        return
+
+    def initialize(self):
+        # self.maxLow = 0
+        # self.maxMid = 0
+        # self.maxHi = 0
+        return StatusCode.Success
+
+
+    def execute(self):
+        evtCollection = self.evtStore[self.MCEventKey] 
+        for mcEvt in evtCollection:
+            mcEvt.print()
+            # for mcParticle in mcEvt.particles:
+            #     barCode = mcParticle.barcode()
+            #     self.maxLow = max(self.maxLow, barCode%200000)
+            #     if barCode%1000000 > 200000:
+            #         self.maxMid = max(self.maxMid, barCode%1000000 - 200000)
+            #     self.maxHi = max(self.maxHi, barCode//1000000)
+        return StatusCode.Success
+
+    def finalize(self):
+        # print("Low part: ", self.maxLow, " out of 200000 (",100*self.maxLow/200000,"% of overflow)")
+        # print("Mid part: ", self.maxMid, " out of ", 1000000 - 200000, " (",100*self.maxMid/(1000000-200000),"% of overflow")
+        # print("Hi  part: ", self.maxHi, " out of ", (1<<31)//1000000, " (", 100*self.maxHi/((1<<31)//1000000),"% of overflow")
+
+        return StatusCode.Success
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