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<p>Folks,</p>
<p>Please find the minutes <a moz-do-not-send="true"
href="https://halldweb.jlab.org/wiki/index.php/GlueX_Software_Meeting,_August_20,_2019#Minutes">here</a>
and below.</p>
<p> -- Mark</p>
<p>___________________________________</p>
<p>
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<h2 id="firstHeading" class="firstHeading" lang="en"><span
dir="auto">GlueX Software Meeting, August 20, 2019, </span><span
class="mw-headline" id="Minutes">Minutes</span></h2>
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lang="en">
<p>Present:
</p>
<ul>
<li> <b> CMU: </b> Naomi Jarvis</li>
<li> <b> JLab: </b> David Abbott, Stuart Fegan, Mark
Ito (chair), David Lawrence, Simon Taylor, Carl
Timmer, Beni Zihlmann</li>
</ul>
<h3><span class="mw-headline" id="Announcements">Announcements</span></h3>
<ol>
<li> <a rel="nofollow" class="external text"
href="https://mailman.jlab.org/pipermail/halld-offline/2019-August/003734.html">/mss/halld/halld-scratch
will be zero'ed</a>. The exact schedule has not been
set.</li>
<li> <a rel="nofollow" class="external text"
href="https://mailman.jlab.org/pipermail/halld-offline/2019-August/003735.html">Cache
files where the disk version was different from that
on tape</a>. These files were lost.</li>
</ol>
<h3><span class="mw-headline" id="Online_Skims">Online
Skims</span></h3>
<p>David described not only the new system for performing
skims of special triggers online, but also the new
architecture for writing data to disk in the counting
room as it comes out of CODA. See <a rel="nofollow"
class="external text"
href="https://docs.google.com/presentation/d/1NuU8b5qo6M_WnNfpc4F1w-vhaFkP7atXN_5DnzzVIxs/edit?usp=sharing">his
slides</a> for details.
</p>
<ul>
<li> The basic idea is to do skims of special triggers
(BCAL-LED triggers, random triggers, sync events,
etc.) in the counting room while we take data. Those
skim files are then immediately available for
calibrations. This could speed up calibrations needed
in advance of the first reconstruction pass on the
data.</li>
<li> To speed up the process, blocks of triggers that do
not contain the special triggers can be skipped. Time
is saved by avoiding dis-entanglement of the events.
This means that there will be a reduction of the
number of PS triggers in the skimmed output; all
blocks have PS triggers, but not all PS triggers are
in blocks with special triggers.</li>
<li> Information from the block headers will be put into
a relational database, including information on the
number of each type of trigger, the first and last
events in each output file, etc. These quantities can
be migrated to the RCDB later.</li>
<li> The architecture of the new Hall D Data recording
scheme will use fast copies using remote direct memory
access (RDMA) to transfer data from IB interface to IB
interface without involving the CPU. RAID servers will
send and receive data from ramdisks and the data
written from memory to arrays of traditional
partitions on multiple RAID servers. From there the
jmigrate system will look for data to be shipped to
the Computer Center for storage on tape.</li>
<li> There are still some issues to deal with, including
more thorough testing, and definition of a
back-pressure mechanism (especially if the skim
process cannot keep up).</li>
</ul>
<h3><span class="mw-headline"
id="Review_of_minutes_from_the_last_Software_Meeting">Review
of minutes from the last Software Meeting</span></h3>
<p>We went over <a
href="https://halldweb.jlab.org/wiki/index.php/GlueX_Software_Meeting,_August_6,_2019#Minutes"
title="GlueX Software Meeting, August 6, 2019">the
minutes from August 6</a>. David reported that the
reconstruction launch at NERSC got going again last
week, but ran into problems over the weekend due to a
change in how tape is handled at JLab.
</p>
<h3><span class="mw-headline"
id="Review_of_recent_discussion_on_the_GlueX_Software_Help_List">Review
of recent discussion on the GlueX Software Help List</span></h3>
<p>We briefly discuss <a rel="nofollow" class="external
text"
href="https://groups.google.com/forum/#!topic/gluex-software/Krdl0FxwMGQ">the
issue with SQLite versions of the CCDB</a>. There is
still no clear-cut, works-everywhere solution.
</p>
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