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Hi,<br>
<br>
Using the danaevio plugin, which writes dana objects to evio files, I
compared hddm and evio file sizes w/ and w/o gzip. I used two files
generated by David L, 100 events each of smeared single pi and
multi-track events. The DANA objects written out in evio are basically
containers for the hddm data read in.<br>
<br>
<u>No gzip</u><tt><br>
<br>
single pi: 2.9M evio 3.1M hddm<br>
multi trk: 23M evio 24M hddm<br>
</tt><br>
The ratio of file sizes is:<br>
<br>
<tt> single pi: 1.07 hddm/evio<br>
multi tri: 1.04 hddm/evio</tt><br>
<br>
This is not surprising as for the most part the same bytes are written
out, but in different order. <br>
<br>
<br>
<u>With gzip (default flags)</u><br>
<br>
<tt> single pi: 967k evio 1.4M hddm<br>
multi tri: 6.6M evio 9.8M hddm<br>
</tt><br>
This gives gzip compression ratios:<br>
<br>
<tt> single pi: 3.0 evio 2.2 hddm<br>
multi trk: 3.5 evio 2.4 hddm<br>
</tt><br>
The ratio of gzipped file sizes is:<br>
<br>
<tt> single pi: 1.45 hddm/evio<br>
multi trk: 1.48 hddm/evio</tt><br>
<br>
<br>
Note that evio files compress better. I speculate this is because data
is grouped differently in the two formats. In evio files data for all
tracks for a particular aspect are all grouped together, e.g. all track
id's are sequential, all track vertex x values are sequential, etc.
Thus it is more likely there are long runs of the same or similar
numbers in evio files, allowing gzip to compress more effectively.<br>
<br>
Also note that the evio package includes auto-gunzip on input, and I am
about to add an auto-gzip option for output.<br>
<br>
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Sincerely,
Elliott
================================================================================
Those raised in a morally relative or neutral environment will hold
no truths to be self-evident.
Elliott Wolin
Staff Physicist, Jefferson Lab
12000 Jefferson Ave
Suite 8 MS 12A1
Newport News, VA 23606
757-269-7365
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