Merge branch 'mces-firstevent' into 'main'

Add Exec.FirstEvent flag and configure McEventSelector for 64-bit events

See merge request atlas/athena!70690

Control/AthenaConfiguration/python/AllConfigFlags.py

@@ -24,8 +24,9 @@ def initConfigFlags():
     from AthenaCommon.Constants import INFO
     acf.addFlag('Exec.OutputLevel', INFO, help='Global OutputLevel')
     acf.addFlag('Exec.PrintAlgsSequence', False, help='print algorithm sequence in ApplicationMgr')
-    acf.addFlag('Exec.MaxEvents', -1, help='number of events to proceess (-1 for all)')
-    acf.addFlag('Exec.SkipEvents', 0, help='number of events to skip')
+    acf.addFlag('Exec.MaxEvents', -1, type=int, help='number of events to proceess (-1 for all)')
+    acf.addFlag('Exec.SkipEvents', 0, type=int, help='number of events to skip')
+    acf.addFlag('Exec.FirstEvent', 1, type=int, help='first event number when not reading from input file')
     acf.addFlag('Exec.DebugStage', '', help='attach debugger at stage: conf, init, exec, fini')
     acf.addFlag('Exec.Interactive', "", help='interactive prompt at stage: init, exec')
     acf.addFlag('Exec.FPE', 0, help='FPE check mode: -2 (no FPE check), -1 (abort with core-dump), 0 (FPE Auditor w/o stack-tace) , >0 (number of stack-traces printed by the job)')

Generators/McEventSelector/python/McEventSelectorConfig.py

-# Copyright (C) 2002-2023 CERN for the benefit of the ATLAS collaboration
+# Copyright (C) 2002-2024 CERN for the benefit of the ATLAS collaboration
 from AthenaConfiguration.ComponentAccumulator import ComponentAccumulator
 from AthenaConfiguration.ComponentFactory import CompFactory
 
@@ -15,6 +15,14 @@ def McEventSelectorCfg(flags, **kwargs):
     if flags.Input.TimeStamps:
         kwargs.setdefault("InitialTimeStamp", flags.Input.TimeStamps[0])
 
+    if flags.Exec.FirstEvent <= 0:
+        raise ValueError("FirstEvent must be a positive, non-zero integer")
+
+    kwargs.setdefault("FirstEvent", flags.Exec.FirstEvent)
+
+    # we use 64-bit numbers by default now
+    kwargs.setdefault("EventsPerRun", int(2**63 - 1))  # sys.maxint on a 64-bit machine
+
     evSel = CompFactory.McEventSelector("EventSelector", **kwargs)
     cfg.addService(evSel)
     cfg.setAppProperty("EvtSel", evSel.getFullJobOptName())