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The skimming tool has been generalized and externalized. The last releases of source code, documentation and pending issues are now available at the new TRAC server. The tutorial below is still valuable, because the recent TSkim releases are still compatible with those old variables. Yet, it is strongly recomended to move to the new interface, described here, here and there. An upgrade of this tutorial is under work. |
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Date: 24 June 2008
Software by: David Chamont
Presentation by: Tom Glanzman
Update: 16 July 2008
Scope
This is intended to be a quick start guide for using the current skimmer version (v6r0p1) to extract merit/digi/recon events from real data as well as construct event lists. Event lists (test text file with "Run EventId" pairs) may be used to drive the WIRED event display. FRED (i.e. Gleam) needs the explicit digi and recon files to read.
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These root files contain 21 events.
Reference information
- Skimmer User's Guide
- The skimmer code is in CVS, package name = DataServer
- At SLAC the skimmer code is located in this directory
Code Block /afs/slac/g/glast/ground/DataServer/
- You might also be interested in the Data Access FAQ
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Various skimmer-related problems have been reported over the past few weeks. Below are some general hints to using the skimmer followed by descriptions of a couple of outstanding problems.
General hints
- Define the following environment variables in your skimmer scripts
For noric machines:
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setenv TMP /usr/work/<your-userid>
setenv TMPDIR /usr/work/<your-userid>
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For batch machines:
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setenv TMP /scratch/<your-userid>
setenv TMPDIR /scratch/<your-userid>
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Note that if you are running multiple skimmer jobs on the same machine, you will be obligated to define unique $TMP and $TMPDIR spaces for each job.
- Use skimmer v6r0p1 rather than v6r1
- If problems, limit number of events processed per job to no more than about 100M events. If problems persist, reduce further.
Outstanding problems.
- Skimming RECON and DIGI files is unreliable due to corrupt TTreeIndex structures. This problem arises when data in L1PROC is merged and the TTreeIndex not rebuilt. Solutions being devised now.
- Skimming large numbers of MERIT events can cause skimmer to crash. One contributing factor may be ROOTs insistence of keeping the entire TTreeIndex in memory at all times when it is being used. There may also be some internal memory corruption if the TTreeIndex grows too large. Being investigated.