update ldmx-sw analysis tutorial with more info about linking

Author: tomeichlersmith

src/using/analysis/ana-cfg.py

@@ -1,5 +1,5 @@
 from LDMX.Framework import ldmxcfg
 p = ldmxcfg.Process('ana')
-p.sequence = [ ldmxcfg.Analyzer.from_file('MyAnalyzer.cxx') ]
+p.sequence = [ ldmxcfg.Analyzer.from_file('MyAnalyzer.cxx', needs=['Ecal_Event']) ]
 p.inputFiles = [ 'events.root' ]
 p.histogramFile = 'hist.root'

src/using/analysis/analyzer-total-rec-energy.cxx

@@ -27,7 +27,7 @@ void MyAnalyzer::onProcessStart() {
 }
 
 void MyAnalyzer::analyze(const framework::Event& event) {
-  const auto& ecal_rec_hits{event.getCollection<ldmx::EcalHit>("EcalRecHits")};
+  const auto& ecal_rec_hits{event.getCollection<ldmx::EcalHit>("EcalRecHits","")};
   double total = 0.0;
   for (const auto& hit : ecal_rec_hits) {
     total += hit.getEnergy();

src/using/analysis/gen.py

@@ -0,0 +1,24 @@
+from LDMX.Framework import ldmxcfg
+p = ldmxcfg.Process('test')
+from LDMX.SimCore import simulator as sim
+mySim = sim.simulator( "mySim" )
+mySim.setDetector( 'ldmx-det-v14-8gev', True )
+from LDMX.SimCore import generators as gen
+mySim.generators = [ gen.single_8gev_e_upstream_tagger() ]
+mySim.beamSpotSmear = [20.,80.,0.]
+mySim.description = 'Basic test Simulation'
+p.sequence = [ mySim ]
+p.run = 1
+p.maxEvents = 10000
+p.outputFiles = [ 'events.root' ]
+
+import LDMX.Ecal.EcalGeometry
+import LDMX.Ecal.ecal_hardcoded_conditions
+import LDMX.Hcal.HcalGeometry
+import LDMX.Ecal.digi as ecal_digi
+
+p.sequence = [
+    mySim,
+    ecal_digi.EcalDigiProducer(),
+    ecal_digi.EcalRecProducer()
+]

src/using/analysis/ldmx-sw.md

@@ -54,6 +54,39 @@ are located.
 ```python
 {{#include ana-cfg.py}}
 ```
+
+~~~admonish error title="Unable to Load Library" collapsible=true
+If you see an error like the one below, you are probably not linking
+your stand-alone processor to its necessary libraries.
+The configuration script needs to be updated with `needs` listing
+the ldmx-sw libraries that the stand-alone processor needs to be
+linked to.
+
+For example, this tutorial uses the Ecal hits defined in the
+`Ecal/Event` area which means we need to add `'Ecal_Event'` to
+the `needs` list.
+
+Example error you could see...
+```
+$ denv fire ana-cfg.py
+---- LDMXSW: Loading configuration --------
+Processor source file /home/tom/code/ldmx/website/src/using/analysis/MyAnalyzer.cxx is newer than its compiled library
+ /home/tom/code/ldmx/website/src/using/analysis/libMyAnalyzer.so (or library does not exist), recompiling...          
+ done compiling /home/tom/code/ldmx/website/src/using/analysis/MyAnalyzer.cxx
+ ---- LDMXSW: Configuration load complete  --------
+ ---- LDMXSW: Starting event processing --------
+ Warning in <TClass::Init>: no dictionary for class pair<int,ldmx::SimParticle> is available
+ Warning in <TClass::Init>: no dictionary for class ldmx::SimParticle is available
+ Warning in <TClass::Init>: no dictionary for class ldmx::SimTrackerHit is available
+ Warning in <TClass::Init>: no dictionary for class ldmx::SimCalorimeterHit is available
+ Warning in <TClass::Init>: no dictionary for class ldmx::HgcrocDigiCollection is available
+ Warning in <TClass::Init>: no dictionary for class ldmx::EcalHit is available
+ Warning in <TClass::Init>: no dictionary for class ldmx::CalorimeterHit is available     
+ 
+ ... proceeds to seg fault on getEnergy ...
+```
+~~~
+
 A quick test can show that the code is compiling and running
 (although it will not print out anything or create any files).
 ```

src/using/analysis/python.md

@@ -61,30 +61,7 @@ mv events.root path/to/work-area/
 ```
 where `config.py` is the following python configuration script.
 ```python
-from LDMX.Framework import ldmxcfg
-p = ldmxcfg.Process('test')
-from LDMX.SimCore import simulator as sim
-mySim = sim.simulator( "mySim" )
-mySim.setDetector( 'ldmx-det-v14-8gev', True )
-from LDMX.SimCore import generators as gen
-mySim.generators = [ gen.single_8gev_e_upstream_tagger() ]
-mySim.beamSpotSmear = [20.,80.,0.]
-mySim.description = 'Basic test Simulation'
-p.sequence = [ mySim ]
-p.run = 1
-p.maxEvents = 10_000
-p.outputFiles = [ 'events.root' ]
-
-import LDMX.Ecal.EcalGeometry
-import LDMX.Ecal.ecal_hardcoded_conditions
-import LDMX.Hcal.HcalGeometry
-import LDMX.Ecal.digi as ecal_digi
-
-p.sequence = [
-    mySim,
-    ecal_digi.EcalDigiProducer(),
-    ecal_digi.EcalRecProducer()
-]
+{{#include gen.py}}
 ```
 ~~~