h1. Software Hints and Tips

h2. Running a tracker simulation

There is a dedicated directory holding top level scripts for producing tracker data within MAUS at:

<pre>

bin/user/scifi

</pre>

For example to run a MAUS simulation of the tracker in the presence of a magnetic field (helical tracks) do the following from the MAUS root directory:

<pre>

source env.sh

cd bin/user/scifi

./simulate_scifi.py --configuration_file datacard_mc_helical

</pre> 

The equivalent command for no magnetic field (straight tracks) is:

<pre>

./simulate_scifi.py --configuration_file datacard_mc_straight

</pre>

h2. Datacard variables

Datacard variables control the various parameters passed to MAUS. The variables assume the default values set in src/common_py/ConfigurationDefaults.py unless overridden in a datacard or elsewhere.  Here are a few common variables: 

* Number of spills. The number of spills to simulate can be set by editing the relevant datacard file and changing the variable 'spill_generator_number_of_spills'.

* The number of particles per spill is controlled by the beam variable. This has a number of sub-variables, two of which can be set to alter the number of particles per spill:

** 'binomial_n' is the number of attempts at generating a track

** 'binomial_p' is the probability an attempt succeeds

* Helical pattern recognition can be turned on or off by setting 'SciFiHelicalPROn' to 1 or 0 respectively

* Straight pattern recognition can be turned on or off by setting 'SciFiStraightPROn' to 1 or 0 respectively

h2. Accessing the output data

Data is output by MAUS either as "ROOT":http://root.cern.ch/ or JSON documents.  In order for ROOT to understand the classes we have written, a ROOT dictionary, built automatically by MAUS, must first be loaded. In an interactive ROOT session this done with following command:

<pre>

.L $MAUS_ROOT_DIR/build/libMausCpp.so

</pre>

The equivalent command if using "PyROOT":http://root.cern.ch/drupal/content/pyroot is 

<pre>

import libMausCpp

</pre>

An example ROOT session to open a data file would be:

<pre>

> .L $MAUS_ROOT_DIR/build/libMausCpp.so

> TFile f1("maus_output.root")

> TBrowser b

</pre>

The equivalent PyROOT session would be:

<pre>

>>> from ROOT import *

>>> import libMausCpp

>>> f1 = TFile("maus_output.root")

>>> b = TBrowser()

</pre>

The tracker MC data can then be found by browsing to:

<pre>

Spill:data:_spill:_mc:_sci_fi_hits

</pre>

The reconstructed data is stored under:

<pre>

Spill:data:_spill:recon:_scifi_event

</pre>

An example PyROOT session to access some data:

<pre>

>>> from ROOT import *

>>> import libMausCpp

>>> f1 = TFile("maus_output.root")

>>> t1 = f1.Get("Spill")

>>> t1

<ROOT.TTree object ("Spill") at 0x8bfa970>

>>> data = MAUS.Data()

>>> t1.SetBranchAddress("data", data)

>>> t1.GetEntry(1)

51435

>>> spill = data.GetSpill()

>>> spill

<ROOT.MAUS::Spill object at 0x92f4a40>

>>> spill.GetReconEvents().size()

1L

>>> revt = spill.GetReconEvents()[0]

>>> sfevt = revt.GetSciFiEvent()

>>> sfevt

<ROOT.MAUS::SciFiEvent object at 0x9310cb0>

>>> htrks = sfevt.helicalprtracks()

>>> htrks.size()

2L

>>> seeds = htrks[0].get_spacepoints()

>>> seeds.size()

5L

>>> sp = seeds[0]

>>> sp.get_position().x()

8.468833333333333

>>> 

</pre>