Consistency fixes for SOR determination in unanchored MC (#1780)

* Set default firstOrbit to 256

just a preventive measure in case someone is using --early-orbits
(avoid to get negative).
In the worst case we skip few timeframes ... and in any case not
a relevant change for anchored MC.

* Better SOR determination

Fixes a problem with wrong/inconsistent timestamps
for some runs (when not using anchoring).

Now consistent with other code in O2.

MC/bin/o2dpg_sim_workflow.py

@@ -118,7 +118,7 @@
 parser.add_argument('--no-tpc-digitchunking', action='store_true', help=argparse.SUPPRESS)
 parser.add_argument('--no-strangeness-tracking', action='store_true', default=False, help="Disable strangeness tracking")
 parser.add_argument('--combine-tpc-clusterization', action='store_true', help=argparse.SUPPRESS) #<--- useful for small productions (pp, low interaction rate, small number of events)
-parser.add_argument('--first-orbit', default=0, type=int, help=argparse.SUPPRESS)  # to set the first orbit number of the run for HBFUtils (only used when anchoring)
+parser.add_argument('--first-orbit', default=256, type=int, help=argparse.SUPPRESS)  # to set the first orbit number of the run for HBFUtils (only used when anchoring); default 256 for convenience to allow for some orbits-early
                                                             # (consider doing this rather in O2 digitization code directly)
 parser.add_argument('--orbits-early', default=0, type=float, help=argparse.SUPPRESS) # number of orbits to start simulating earlier
                                                                                    # to reduce start of timeframe effects in MC --> affects collision context
@@ -244,21 +244,44 @@ def retrieve_sor(run_number):
     """
     retrieves start of run (sor)
     from the RCT/Info/RunInformation table with a simple http request
-    in case of problems, 0 will be returned
+    in case of problems, 0 will be returned. Simple http request has advantage
+    of not needing to initialize a Ccdb object.
     """
+
     url="http://alice-ccdb.cern.ch/browse/RCT/Info/RunInformation/"+str(run_number)
     ansobject=requests.get(url)
     tokens=ansobject.text.split("\n")
 
+    # determine start of run, earlier values take precedence (see also implementation in BasicCCDBManager::getRunDuration)
+    STF=0
+    # extract SOR by pattern matching
+    for t in tokens:
+      match_object=re.match(r"\s*(STF\s*=\s*)([0-9]*)\s*", t)
+      if match_object != None:
+         STF=int(match_object[2])
+         break
+    if STF > 0:
+      return STF
+
+    SOX=0
+    # extract SOX by pattern matching
+    for t in tokens:
+      match_object=re.match(r"\s*(STF\s*=\s*)([0-9]*)\s*", t)
+      if match_object != None:
+         SOX=int(match_object[2])
+         break
+    if SOX > 0:
+      return SOX
+
     SOR=0
     # extract SOR by pattern matching
     for t in tokens:
       match_object=re.match(r"\s*(SOR\s*=\s*)([0-9]*)\s*", t)
       if match_object != None:
-         SOR=match_object[2]
+         SOR=int(match_object[2])
          break
-
-    return int(SOR)
+    
+    return SOR
 
 
 # check and sanitize config-key values (extract and remove diamond vertex arguments into finalDiamondDict)