DDSim: Gun options, add distribution steering (needs DD4hep r2121)

Add control over distributions
if a distribution is set activate isotrop
if isotrop is activated use uniform by default

Move set up gun function to Helper/Gun, keeps functionality closer together

DDSim/DD4hepSimulation.py

@@ -322,7 +322,7 @@ class DD4hepSimulation(object):
 
     if self.enableGun:
       gun = DDG4.GeneratorAction(kernel,"Geant4ParticleGun/"+"Gun")
-      self.__setGunOptions( gun )
+      self.gun.setOptions( gun )
       gun.Standalone = False
       gun.Mask = 1
       actionList.append(gun)
@@ -431,30 +431,6 @@ class DD4hepSimulation(object):
     kernel.run()
     kernel.terminate()
 
-  def __setGunOptions(self, gun):
-    """set the starting properties of the DDG4 particle gun"""
-    try:
-      gun.energy       = self.gun.energy
-      gun.particle     = self.gun.particle
-      gun.multiplicity = self.gun.multiplicity
-      gun.position     = self.gun.position
-      gun.isotrop      = self.gun.isotrop
-      gun.direction    = self.gun.direction
-      if self.gun.thetaMin is not None:
-        gun.ThetaMin = self.gun.thetaMin
-        gun.isotrop = True
-      if self.gun.thetaMax is not None:
-        gun.ThetaMax = self.gun.thetaMax
-        gun.isotrop = True
-      if self.gun.phiMin is not None:
-        gun.PhiMin = self.gun.phiMin
-        gun.isotrop = True
-      if self.gun.phiMax is not None:
-        gun.PhiMax = self.gun.phiMax
-        gun.isotrop = True
-    except Exception as e: #pylint: disable=W0703
-      print "ERROR: parsing gun options:\n%s\nException: %s " % (self.gun, e )
-      exit(1)
 
   def __setupRandomGenerator(self, rndm):
     """set the properties for the random number generator"""

DDSim/Helper/Gun.py

@@ -17,6 +17,35 @@ class Gun( ConfigHelper ):
     self.phiMax = None
     self.thetaMin = None
     self.thetaMax = None
+    self._distribution = None
+
+
+  @property
+  def distribution( self ):
+    """choose the distribution of the random direction for theta
+
+    Options for isotropic distributions in: 'uniform', 'cos(theta)', 'eta' (or
+    'pseudorapidity'), 'ffbar' (distributed flat in 1+cos^2 theta)
+
+    'uniform' is the default distribution
+
+    Setting a distribution will set isotrop = True
+    """
+    return self._distribution
+  @distribution.setter
+  def distribution( self, val ):
+    if val is None:
+      return
+    possibleDistributions = ['uniform', 'cos(theta)', 'eta', 'pseudorapidity', 'ffbar'] ## (1+cos^2 theta)
+    if not isinstance( val, basestring):
+      raise RuntimeError( "malformed input '%s' for gun.distribution. Need a string : %s " % (val, ",".join(possibleDistributions)) )
+    if val not in possibleDistributions:
+      ## surround options by quots to be explicit
+      stringified = [ "'%s'" % _ for _ in possibleDistributions ]
+      raise RuntimeError( "Unknown distribution '%s', Use one of: %s " % (val,
+                                                                          ", ".join(stringified)) )
+    self._distribution = val
+    self._isotrop = True
 
   @property
   def isotrop( self ):
@@ -33,6 +62,8 @@ class Gun( ConfigHelper ):
       self._isotrop = ConfigHelper.makeBool( val )
     except RuntimeError:
       raise RuntimeError( "malformed input '%s' for gun.isotrop " % val)
+    if val and self.distribution is None:
+      self.distribution = 'uniform'
 
   @property
   def direction( self ):
@@ -56,3 +87,30 @@ class Gun( ConfigHelper ):
     self._position = ConfigHelper.makeTuple( val )
     if len(self._position) != 3:
       raise RuntimeError(" gun.position: malformed input '%s', needs to be a string representing a three vector " % val )
+
+
+  def setOptions( self, ddg4Gun ):
+    """set the starting properties of the DDG4 particle gun"""
+    try:
+      ddg4Gun.energy       = self.energy
+      ddg4Gun.particle     = self.particle
+      ddg4Gun.multiplicity = self.multiplicity
+      ddg4Gun.position     = self.position
+      ddg4Gun.isotrop      = self.isotrop
+      ddg4Gun.direction    = self.direction
+      ddg4Gun.Distribution = self.distribution
+      if self.thetaMin is not None:
+        ddg4Gun.ThetaMin = self.thetaMin
+        ddg4Gun.isotrop = True
+      if self.thetaMax is not None:
+        ddg4Gun.ThetaMax = self.thetaMax
+        ddg4Gun.isotrop = True
+      if self.phiMin is not None:
+        ddg4Gun.PhiMin = self.phiMin
+        ddg4Gun.isotrop = True
+      if self.phiMax is not None:
+        ddg4Gun.PhiMax = self.phiMax
+        ddg4Gun.isotrop = True
+    except Exception as e: #pylint: disable=W0703
+      print "ERROR: parsing gun options:\n%s\nException: %s " % (self, e )
+      exit(1)