Possibility to take external config for Pythia8

In case of generator pythia8, we have so far always
constructed a Pythia8 config file from the parameters
given to o2dpg_sim_workflow.py

However, some expert users may want to use an external
configuration for Pythia8.

This commit provides the possibility to do so via sensitivity
to the `GeneratorPythia8.config` ConfigurableParam (so far ignored).

An example is:

```
${O2DPG_ROOT}/MC/bin/o2dpg_sim_workflow.py -eCM 14000 -col pp -gen pythia8 -proc cdiff -tf 2      \
                                           -ns 20 -e ${SIMENGINE}                                 \
                                           -j ${NWORKERS} -interactionRate 500000                 \
                                           -run 302000 -seed 624                                  \
                                           -confKey "GeneratorPythia8.config=/SOMEPATH/pythia8_powheg.cfg"
```

The new feature allows expert studies with specially setup
Pythia8 configs. The development was motivated from https://its.cern.ch/jira/browse/O2-4549

However, note that options `-proc` `-eCM` etc. might have no effect or are ignored in such cases.

Author: sawenzel

MC/bin/o2dpg_sim_config.py

@@ -97,6 +97,8 @@ def create_geant_config(args, externalConfigString):
     # creates generic transport simulation config key values
     # based on arguments args (run number, energy, ...) originally passed
     # to o2dpg_sim_workflow.py
+    #
+    # returns a dictionary of mainkey -> dictionary of subkey : values
     config = {}
     def add(cfg, flatconfig):
        for entry in flatconfig:

MC/bin/o2dpg_sim_workflow.py

@@ -505,6 +505,9 @@ def getDPL_global_options(bigshm=False, ccdbbackend=True):
 workflow['stages'].append(TPC_SPACECHARGE_DOWNLOADER_TASK)
 
 
+# query initial configKey args for signal transport; mainly used to setup generators
+simInitialConfigKeys = create_geant_config(args, args.confKey)
+
 # loop over timeframes
 for tf in range(1, NTIMEFRAMES + 1):
    TFSEED = SIMSEED + tf
@@ -627,38 +630,46 @@ def getDPL_global_options(bigshm=False, ccdbbackend=True):
    SGN_CONFIG_task=createTask(name='gensgnconf_'+str(tf), tf=tf, cwd=timeframeworkdir)
    SGN_CONFIG_task['cmd'] = 'echo "placeholder / dummy task"'
    if GENERATOR == 'pythia8':
-      SGN_CONFIG_task['cmd'] = '${O2DPG_ROOT}/MC/config/common/pythia8/utils/mkpy8cfg.py \
-                                --output=pythia8.cfg                                     \
-                                --seed='+str(TFSEED)+'                                   \
-                                --idA='+str(PDGA)+'                                      \
-                                --idB='+str(PDGB)+'                                      \
-                                --eCM='+str(ECMS)+'                                      \
-                                --eA='+str(EBEAMA)+'                                     \
-                                --eB='+str(EBEAMB)+'                                     \
-                                --process='+str(PROCESS)+'                               \
-                                --ptHatMin='+str(PTHATMIN)+'                             \
-                                --ptHatMax='+str(PTHATMAX)
-      if WEIGHTPOW   > 0:
-         SGN_CONFIG_task['cmd'] = SGN_CONFIG_task['cmd'] + ' --weightPow=' + str(WEIGHTPOW)
+      # see if config is given externally
+      externalPythia8Config = simInitialConfigKeys.get("GeneratorPythia8", {}).get("config", None)
+      if externalPythia8Config != None:
+         print ("Using external Pythia8 configuration " + str(externalPythia8Config))
+         # in this case, we copy the external config to the local dir (maybe not even necessary)
+         SGN_CONFIG_task['cmd'] = 'cp ' + externalPythia8Config + ' pythia8.cfg'
+      else:
+         SGN_CONFIG_task['cmd'] = '${O2DPG_ROOT}/MC/config/common/pythia8/utils/mkpy8cfg.py \
+                                  --output=pythia8.cfg                                      \
+                                  --seed='+str(TFSEED)+'                                    \
+                                  --idA='+str(PDGA)+'                                       \
+                                  --idB='+str(PDGB)+'                                       \
+                                  --eCM='+str(ECMS)+'                                       \
+                                  --eA='+str(EBEAMA)+'                                      \
+                                  --eB='+str(EBEAMB)+'                                      \
+                                  --process='+str(PROCESS)+'                                \
+                                  --ptHatMin='+str(PTHATMIN)+'                              \
+                                  --ptHatMax='+str(PTHATMAX)
+         if WEIGHTPOW   > 0:
+            SGN_CONFIG_task['cmd'] = SGN_CONFIG_task['cmd'] + ' --weightPow=' + str(WEIGHTPOW)
+
       # if we configure pythia8 here --> we also need to adjust the configuration
       # TODO: we need a proper config container/manager so as to combine these local configs with external configs etc.
       args.confKey = args.confKey + ";GeneratorPythia8.config=pythia8.cfg"
 
    # elif GENERATOR == 'extgen': what do we do if generator is not pythia8?
        # NOTE: Generator setup might be handled in a different file or different files (one per
        # possible generator)
-
    workflow['stages'].append(SGN_CONFIG_task)
 
+   # determine final conf key for signal simulation
+   CONFKEY = constructConfigKeyArg(create_geant_config(args, args.confKey))
+
    # -----------------
    # transport signals
    # -----------------
    signalneeds=[ SGN_CONFIG_task['name'], GRP_TASK['name'] ]
    if (args.pregenCollContext == True):
       signalneeds.append(PreCollContextTask['name'])
 
-   # determine final configKey args for signal transport
-   CONFKEY = constructConfigKeyArg(create_geant_config(args, args.confKey))
 
    # add embedIntoFile only if embeddPattern does contain a '@'
    embeddinto= "--embedIntoFile ../bkg_MCHeader.root" if (doembedding & ("@" in args.embeddPattern)) else ""