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<p>I know that you all have been waiting for this, and <a
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href="https://halldweb.jlab.org/wiki/index.php/HDGeant4_Meeting,_November_5,_2019#Minutes">here
it is</a> as well as below.</p>
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<h2 id="firstHeading" class="firstHeading" lang="en"><span
dir="auto">HDGeant4 Meeting, November 5, 2019, </span><span
class="mw-headline" id="Minutes">Minutes</span></h2>
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<p>Present:
</p>
<ul>
<li> <b> CMU: </b> Naomi Jarvis</li>
<li> <b> FSU: </b> Sean Dobbs</li>
<li> <b> JLab: </b> Alex Austregesilo, Mark Ito
(chair), Igal Jaegle, Simon Taylor, Beni Zihlmann</li>
<li> <b> UConn: </b> Richard Jones</li>
</ul>
<p>There is a <a rel="nofollow" class="external text"
href="https://bluejeans.com/s/EGhEW/">recording of
this meeting</a> on the BlueJeans site. Use your JLab
credentials to get access.
</p>
<h3><span class="mw-headline" id="Announcements">Announcements</span></h3>
<ul>
<li> Naomi alerted us to a recent Analysis Note from
Nilanga Wickramaarachchi where he sees a discrepancy
between HDG3 and HDG4. Alex commented that it amounts
to a factor of two difference in acceptance for the
t-channel and a strange dip in acceptance in the
u-channel. He will mention this at tomorrow's
Production and Analysis Meeting. He also noted that
Peter Pauli has seen similar acceptance differences.</li>
<li> Beni announced that he has succeeded building the
entire GlueX Software stack on Ubuntu 19.04 (Disco).
This distribution ships with GCC 8.3. He noted a huge
spike in memory use when compiling DRootGeom.cc from
the HDGEOMETRY library. % GB of swap space was needed.
Richard thought that this might have something to do
with compiler optimization on a large,
script-generated source code file.</li>
</ul>
<h3><span class="mw-headline"
id="Review_of_minutes_from_the_last_meeting">Review of
minutes from the last meeting</span></h3>
<p>We went over <a
href="https://halldweb.jlab.org/wiki/index.php/HDGeant4_Meeting,_October_22,_2019#Minutes"
title="HDGeant4 Meeting, October 22, 2019">the minutes
from October 22</a> without significant comment.
</p>
<h3><span class="mw-headline"
id="Visualization_with_OpenGL">Visualization with
OpenGL</span></h3>
<p>Igal has been having trouble running hdgeant4 using
OpenGL to do event visualization. He gets an error that
points to OpenGL libraries and the program crashes. He
has not seen this problem with Geant4 version 9, only
version 10.
</p>
<p>Richard told us he uses OpenGL often and is committed
to maintaining this piece of functionality. He will
consult with Igal offline.
</p>
<p>Richard also mentioned that he uses a package called <a
rel="nofollow" class="external text"
href="https://virtualgl.org/About/Introduction">VirtualGL</a>
to access local graphics acceleration hardware while
using a VNC to run Geant4 on a remote node.
</p>
<h3><span class="mw-headline"
id="Python_Interface_Problem">Python Interface Problem</span></h3>
<p>Igal reports an issue using the Python interface to
hdgeant4. There appears to be a conflict between
different versions of the boost libraries. Richard
cautioned us that hdgeant4 will not work through the
Python interface if multi-threaded operation is turned
on in the build. You need a single-threaded build for it
to work due to issues with the SciPy library. Igal will
try that.
</p>
<h3><span class="mw-headline" id="Neutron_Simulation">Neutron
Simulation</span></h3>
<p>We reviewed <a rel="nofollow" class="external text"
href="https://github.com/JeffersonLab/HDGeant4/issues/125">Issue
#125</a>. In light of this issue, Igal suggested that
we use the "high precision" option in the physics list
if we want to do neutron propagation with Geant4. We
need to look into this.
</p>
<h3><span class="mw-headline"
id="Segfault_from_G4VoxelNavigation::ComputeStep">Segfault
from G4VoxelNavigation::ComputeStep</span></h3>
<p>We reviewed <a rel="nofollow" class="external text"
href="https://github.com/JeffersonLab/HDGeant4/issues/118">Issue
#118</a>. Naomi will return to this when she succeeds
in getting a free moment or two.
</p>
<h3><span class="mw-headline"
id="Overall_BCAL_energy_shift.3F">Overall BCAL energy
shift?</span></h3>
<p>We reviewed <a rel="nofollow" class="external text"
href="https://github.com/JeffersonLab/HDGeant4/issues/113">Issue
#113</a>. There is an energy shift in the BCAL
response when comparing G3 to G4. Richard will be taking
another look at this one.
</p>
<p>Igal suggested looking at the difference without
smearing.
</p>
<p>Igal also asked about whether the same low-energy
cut-offs. Richard reminded us that the scheme used in G4
is to stop tracking when particle range gets small
rather than when particle energy gets small, as is done
in G3. This makes matching of thresholds between the two
systems hard if not impossible.
</p>
<h3><span class="mw-headline"
id="Difference_in_Acceptance_between_G3_and_G4">Difference
in Acceptance between G3 and G4</span></h3>
<p>We reviewed <a rel="nofollow" class="external text"
href="https://github.com/JeffersonLab/HDGeant4/issues/111">Issue
#111</a>. Colin Gleason reported this issue in his
analysis. We will go back to him and ask if this is
still a problem for him. If so, it may need to be
repeated with modern versions of software.
</p>
<h3><span class="mw-headline"
id="Feature_request_-_progress_indicator">Feature
request - progress indicator</span></h3>
<p>This is <a rel="nofollow" class="external text"
href="https://github.com/JeffersonLab/HDGeant4/issues/107">Issue
#107</a>. Richard is on it.
</p>
<h3><span class="mw-headline"
id="Reading_in_.23_events_and_source">Reading in #
events and source</span></h3>
<p>Richard estimated that <a rel="nofollow"
class="external text"
href="https://github.com/JeffersonLab/HDGeant4/issues/105">Issue
#105</a> would take about an hour to address.
</p>
<h3><span class="mw-headline" id="Terminal_cleanup.3F">Terminal
cleanup?</span></h3>
<p><a rel="nofollow" class="external text"
href="https://github.com/JeffersonLab/HDGeant4/issues/102">Issue
#102</a> is on Richard's list.
</p>
<h3><span class="mw-headline"
id="Calorimeter_timing_mismatch_between_g3_and_g4">Calorimeter
timing mismatch between g3 and g4</span></h3>
<p>We then discussed <a rel="nofollow" class="external
text"
href="https://github.com/JeffersonLab/HDGeant4/issues/93">Issue
#93</a>, having to do with charged particle timing
measurements in out two calorimeters. Alex wondered if
the problem seen here is the same as those reported by
Colin and Nilanga, i.e, large differences in overall
acceptance for a particular channel as a whole between
G3 and G4.
</p>
<p>Mark suggested that calculating efficiency from Monte
Carlo could be very difficult if accuracy depends on
getting the tails of distributions correct. We might be
better off studying efficiency in data alone. Richard
thought that that approach might be subject to large
systematic effects.
</p>
<p>Igal suggested that in this case as well, comparisons
of the unsmeared reconstruction might be informative.
</p>
<p>Alex will try to look at single particle responses in
data and see how they compare to the two Monte Carlos.
</p>
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