Update README for TPC SCD calib

martenole · martenole · commit 58a768898ed3 · 2023-01-19T19:10:33.000+01:00
diff --git a/Detectors/TPC/calibration/SpacePoints/README.md b/Detectors/TPC/calibration/SpacePoints/README.md
@@ -19,3 +19,55 @@ The workflow running on the aggregator is at the moment causing backpressure on
 ARGS_EXTRA_PROCESS_o2_calibration_residual_aggregator="--compression 0"
 ```
 Note, that currently writing to EOS is disabled. Once the workflow is validated it should be enabled in `aggregator-workflow.sh`: https://github.com/AliceO2Group/AliceO2/blob/cb98b7e5f036024dfce73abf2b6bdb3ad432d1b4/prodtests/full-system-test/aggregator-workflow.sh#L177-L181
+
+
+## Running the calibration offline from ROOT file input
+
+For running the track interpolation offline which creates the unbinned residuals one needs to have the following inputs in the local directory as ROOT files:
+
+- clusters, tracks, track matches for all barrell detectors ITS, TPC, TRD and TOF
+- the TF ID information typically stored in o2_tfidinfo.root
+
+Now, one can rerun the interpolation workflow piping its output directly into the residual aggregator which creates the o2tpc_residuals*.root files with the specified output (residuals binned/unbinned, track information):
+
+```
+o2-tpc-scdcalib-interpolation-workflow -b --send-track-data --disable-mc --hbfutils-config o2_tfidinfo.root | \
+o2-calibration-residual-aggregator -b --enable-track-input  --output-type unbinnedResid,binnedResid,trackParams --output-dir $PWD --disable-root-input
+```
+
+Since the workflow loads also the TPC native clusters which are rather large, you will most likely need to increase the SHM size via adding `--shm-segment-size 32000000000` to both workflows.
+
+#### Track selection
+
+Track selections are applied at the interpolation stage. This can be steered via configurable parameters. For example add
+
+```
+--configKeyValues "scdcalib.maxTracksPerCalibSlot=-1;scdcalib.minTPCNCls=70"
+```
+in order to process all global tracks which are available per TF and have at least 70 TPC clusters.
+For all options please have a look at `Detectors/TPC/calibration/SpacePoints/include/SpacePoints/SpacePointsCalibConfParam.h`
+
+### Creating the distortion map from unbinned residuals
+
+When the unbinned residuals are available it is possible to create the distortion map directly from those and on-the-fly change the track selection, e.g. taking into account only ITS-TPC-TRD tracks or only tracks with a very high quality. Use the `Detectors/TPC/calibration/SpacePoints/macro/staticMapCreator.C` macro in compiled mode. You will need to specify the input file (single ROOT file or list of files) and the run number. Optionally you can specify the output file name or the track type to be used (default is ALL which are available as input, use e.g. "ITS-TPC-TRD" for only this type).
+
+The track selection is steered via configurable param. Before running the macro it's best to create a configuration file which can then be adapted to ones needs:
+```
+const o2::tpc::SpacePointsCalibConfParam& params = o2::tpc::SpacePointsCalibConfParam::Instance();
+params.writeINI("scdconfig.ini", "scdcalib"); // to write default parameters to a file
+```
+For example to request only tracks with 5 ITS clusters, 2 TRD tracklets and a DCA < 10 cm set
+```
+minITSNCls=5
+minTRDNTrklts=2
+writeBinnedResiduals=true
+useTrackData=true
+cutOnDCA=true
+maxDCA=10
+```
+It is also possible to select only TFs from a specific time range. The time range needs to be provided in ms. The epoch time in seconds for a given date can be determined e.g. via `date -d "Nov 22 2022 16:00"  +%s`. Don't forget to multiply by 1000 to get ms.
+```
+timeFilter=true
+startTimeMS=1666669765254
+endTimeMS=1666670365241
+```
