The TPC reconstruction workflow starts from the TPC digits, the clusterer reconstructs clusters in the ClusterHardware format. The clusters are directly written in the RAW page format. The raw data are passed onto the decoder providing the TPC native cluster format to the tracker.

Note: The format of the raw pages is preliminary and does not reflect what is currently implemented in the CRU.

The workflow consists of the following DPL processors:

• tpc-digit-reader -> using tool o2::framework::RootTreeReader
• tpc-clusterer -> interfaces o2::tpc::HwClusterer
• tpc-cluster-decoder -> interfaces o2::tpc::HardwareClusterDecoder
• tpc-tracker -> interfaces o2::tpc::GPUCATracking
• tpc-track-writer -> implements simple writing to ROOT file

Depending on the input and output types the default workflow is extended by the following readers and writers:

• tpc-raw-cluster-writer writes the binary raw format data to binary branches in a ROOT file
• tpc-raw-cluster-reader reads data from binary branches of a ROOT file
• tpc-cluster-writer writes the binary native cluster data to binary branches in a ROOT file
• tpc-cluster-reader reads data from binary branches of a ROOT file

MC labels are passed through the workflow along with the data objects and also written together with the output at the configured stages (see output types).

The input can be created by running the simulation (o2sim) and the digitizer workflow (digitizer-workflow). The digitizer workflow produces the file tpcdigits.root by default, data is stored in separated branches for all sectors.

The workflow can be run starting from digits, raw clusters, or (native) clusters, or directly attached to the o2-sim-digitizer-workflow, see comment on inputs types below.

The workflow is implemented in the o2-tpc-reco-workflow executable.

Display all options

o2-tpc-reco-workflow --help

Important options for the tpc-digit-reader as initial publisher

--infile arg                          Name of the input file
--treename arg (=o2sim)               Name of the input tree
--digitbranch arg (=TPCDigit)         Digit branch
--mcbranch arg (=TPCDigitMCTruth)     MC label branch
--nevents                             Number of events

The tpc-raw-cluster-reader uses the same options except the branch name configuration --databranch arg (==TPCClusterHw) RAW Cluster branch --mcbranch arg (==TPCClusterHwMCTruth) MC label branch

Options for the tpc-track-writer process

--outfile arg (=tpctracks.root)               Name of the output file
--treename arg (=tpcrec)                      Name of tree
--nevents arg (=-1)                           Number of events to execute
--terminate arg (=process)                    Terminate the 'process' or 'workflow'
--track-branch-name arg (=TPCTracks)          configurable branch name for the tracks
--trackmc-branch-name arg (=TPCTracksMCTruth) configurable branch name for the MC labels

Examples:

o2-tpc-reco-workflow --infile tpcdigits.root --tpc-sectors 0-17 --tracker-options "cont refX=83 bz=-5.0068597793"

o2-tpc-reco-workflow --infile tpcdigits.root --tpc-sectors 0-17 --disable-mc 1 --tracker-options "cont refX=83 bz=-5.0068597793"

--input-type arg (=digits)            digitizer, digits, raw, clusters
--output-type arg (=tracks)           digits, raw, clusters, tracks
--disable-mc arg (=0)                 disable sending of MC information
--tpc-lanes arg (=1)                  number of parallel lanes up to the tracker
--tpc-sectors arg (=0-35)             TPC sector range, e.g. 5-7,8,9

Input type digitizer will create the clusterers with dangling input, this is used to connect the reconstruction workflow directly to the digitizer workflow.

All other input types will create a publisher process reading data from branches of a ROOT file. File and branch names are configurable. The MC labels are always read from a parallel branch, the sequence of data and MC objects is assumed to be identical.

The output type selects up to which final product the workflow is executed. Multiple outputs are supported in order to write data at intermediate steps, e.g.

--output-type raw,tracks

MC label data are stored in corresponding branches per sector. The sequence of MC objects must match the sequence of data objects.

By default, all data is written to ROOT files, even the data in binary format like the raw data and cluster data. This allows to record multiple sets (i.e. timeframes/events) in one file alongside with the MC labels.

Parallel processing is controlled by the option --tpc-lanes n. The digit reader will fan out to n processing lanes, each with clusterer, and decoder. The tracker will fan in from multiple parallel lanes. For each sector, a dedicated DPL data channel is created. The channels are distributed among the lanes. The default configuration processes sector data belonging together in the same time slice, but in earlier implementations the sector data was distributed among multiple time slices (thus abusing the DPL time slice concept). The tracker spec implements optional buffering of the input data, if the set is not complete within one invocation of the processing function.

By default, all TPC sectors are processed by the workflow, option --tpc-sectors reduces this to a subset.

The tracker spec interfaces the o2::tpc::GPUCATracking worker class which can be initialized using an option string. The processor spec defines the option --tracker-option. Currently, the tracker should be run with options:

--tracker-option "refX=83 cont"

The most important tracker options are:

cont    activation of continuous mode
refX=   reference x coordinate, tracker tries to propagate all track to the reference
bz=     magnetic field

• the propagation of MC labels goes together with multiple rearrangements and thus copy

• raw pages are using RawDataHeader version 2 with 4 64bit words, need to be converted to version 4 also the CRU will pad all words, RawDataHeader and data words to 128 bits, this is not yet reflected in the produced raw data

• implement configuration from the GRP

--direct-file-dump     write final calibration to local root file
--max-events           maximum number of events to process
--no-write-ccdb        don't send the calibration data via DPL (required in case the calibration write is not attached)
--use-old-subspec      use old subspec definition (CruId << 16) | ((LinkId + 1) << (CruEndPoint == 1 ? 8 : 0))
--lanes arg (=1)       number of parallel processes
--sectors arg (=0-35)  list of TPC sectors, comma separated ranges, e.g. 0-3,7,9-15

In one shell start the data distribution playback, e.g.

StfBuilder --id builder --data-source-enable --data-source-dir=2020-11-11T14_18_25Z --data-source-rate=100 --dpl-channel-name=dpl-chan  --channel-config "name=dpl-chan,type=pair,method=connect,address=ipc:///tmp/stf-builder-dpl-pipe-0,transport=zeromq,rateLogging=1"

In another shell start the pedestal calibration

o2-dpl-raw-proxy -b --dataspec "A:TPC/RAWDATA" --channel-config "name=readout-proxy,type=pair,method=bind,address=ipc:///tmp/stf-builder-dpl-pipe-0,transport=zeromq,rateLogging=1" \
| o2-tpc-calib-pedestal  --max-events 5 --direct-file-dump --shm-segment-size $((8<<30)) --no-calib-output --use-old-subspec

Create a raw-reader.cfg e.g.

i=0; echo -e "[defaults]\ndataOrigin = TPC\ndataDescription = RAWDATA\n" > raw-reader.cfg; echo; for file in *.raw; do echo "[input-$i]"; echo "dataOrigin = TPC"; echo "dataDescription = RAWDATA"; echo "filePath=$file"; echo; i=$((i+1)); done >> raw-reader.cfg

Then run

o2-raw-file-reader-workflow  --input-conf raw-reader.cfg --nocheck-hbf-per-tf --nocheck-hbf-jump --shm-segment-size $((8<<30)) \
|  o2-tpc-calib-pedestal  --max-events 5 --direct-file-dump --shm-segment-size $((8<<30)) --no-calib-output

Remove the --no-write-ccdb option and add

| o2-calibration-ccdb-populator-workflow

This requires to do zero suppression in the first stage. For this the DigiDump class is used, wrapped in an o2 workflow.

Use either the DD part or raw file playback from above and add as processor

| o2-tpc-raw-to-digits-workflow --pedestal-file pedestals.root --configKeyValues "TPCDigitDump.ADCMin=3;TPCDigitDump.NoiseThreshold=3" \
| o2-tpc-reco-workflow --input-type digitizer --output-type tracks --disable-mc

To directly dump the digits to file for inspection use for the reco workflow

| o2-tpc-reco-workflow --input-type digitizer --output-type digits --disable-mc