PSS.LMC Tango Device Drivers¶
Note: tango doc tango example
The LMC schema emerging during the bridging phase will be progressively implemented inside the MVP prototype. It will comprise some emulation of main functions. It is foreseen also a minimal PSS pipeline functionality. We aim to collect the basic interaction modes with Cheetah in order to be able to control it by a simple device driver to be implemented in PI8. Basic information on Cheetah control has been reported in the AT4-362 documentation. The Cheetah pipeline is a single executable which contains either the CPU and the CUDA version of PSS and SPS pipeline. It is a CLI program and can be controlled either by a configuration program and by command line switches. The command line switch overrides the configuration file ones. The proposed design interact with Cheetah by means of command line and, in future, by OS level signals. We will implement the basic Cheetah pipeline (To became the CTRL module as defined in PSS.DDD) inheriting from the Capability d evice of Base classes (and from the subelement Capability when available).
Quickstart¶
TBD
PssPipeline device - CTRL¶
The PssPipeline device (CTRL) inherits from base classes Capability device R/W attributes are normally set by the subarray but can be directly accessed for testing purpose.
Parameters¶
Attribute Name |
Attribute Type |
Note/Description |
|---|---|---|
scanID |
Type: DevULong RO |
scan ID to be inserted in the output products |
schedulingBlockID |
Type: DevString RO |
Scheduling block unique identifier |
frequencyBand |
Type: IntEnum Class RW |
|
subarrayMembership |
Type: DevUshort range [1,16] RW |
ID of the affiliated subarray Note: FSP device can be shared among several subarrays, so this attribute can be implemented as an array. |
sdpDestinationAddresses |
Type: DevString JSON formatted. RW |
Report the list of all the SDP addresses provided by SDP to receive the output products. Specifies the Mac, IP, Port for each resource: |
sdpLinkStatus |
Type: DevBoolean/DevUShort RO |
True/1: the link is active False/0: the link is down |
sdpLinkCapacity |
Type: DevFloat RO |
|
scanProgress |
Type: DevUshort RO |
|
cmdFailureFlag |
Type: DevBooelan RO |
Flag to signal a sub-element failure. Reset by: ObsReset, Restart, Off Consider to add a flag for each command. |
cmdFailureMessage |
Type: DevString RO |
The last command report failure message. |
healthFailureMessage |
Type: DevString RO |
Provide info about capability health failure. |
advancementStatus |
Type: DevFloat RO |
See discussion ahead. |
Commands¶
Command Name |
Input/output args |
Description |
Note |
|---|---|---|---|
On |
Input: None Output: (resultCode, resultMsg) |
PSS pipeline: enable (?) |
|
Standby |
Input: None Output: (resultCode, resultMsg) |
Switch GPU off |
|
Off |
Input: None Output: (resultCode, resultMsg) |
PSS pipeline: disable (?) |
|
ConfigureScan |
Input: DevString JSON formatted with scan configuration Output: (resultCode, resultMsg) |
||
validate_configuration |
Input: DevString JSON formatted with scan configuration Output: none |
Internal method of ConfigureScanCommand to validate the input json. |
|
GoToIdle |
Input: None Output: (resultCode, resultMsg) |
Synchronous command to transition the capability to IDLE. Release allocated resources. |
PssPipeline transits to IDLE obsState |
Scan |
Input: Array of strings Output: (resultCode, resultMsg) |
Long running |
Start a Scan |
EndScan |
Input: Array of strings Output: (resultCode, resultMsg) |
End a Scan Signal terminate |
|
Abort |
Input: None Output: (resultCode, resultMsg) |
End a Scan Signal abort |
|
ObsReset |
Input: None Output: (resultCode, resultMsg) |
Reset Pipeline from FAULT to IDLE obsState. |
|
Restart |
Input: None Output: (resultCode, resultMsg) |
||
ConfigureLog |
Input: DevUshort Output: (resultCode, resultMsg) |
Configure log level: 0 = debug 1 = log 2 = warnings 3 = errors |
Cheetah command line interface¶
We start the Cheetah program with a command line of the form
./cheetah/pipeline/cheetah_pipeline –config cheetah.xml -p Dedispersion –log-level log
The different pipelines which can be selected are:
Empty
Dedispersion
RfiDetectionPipeline
SinglePulseHandler
For the input stream (the data source) there are the possibility to create synthetic internally generated data or external sources. We chose to use a standard file generated by sigproc fake (ska.dat hardcoded in the standard config file). The output of cheetah is on the standard output and it has a standard syslog format:
[log][tid=140474636963584][/home/baffa/src/ska/cheetah/cheetah/../cheetah/pipeline/detail/BeamLauncher.cpp:148][1600767420]Creating Beams….
[warn][tid=140474636963584][/home/baffa/src/ska/cheetah/cheetah/../cheetah/tdas/detail/Tdas.cpp:76][1600767420]No Time Domain Accelerated Search algorithm has been specified
[log][tid=140474636963584][/home/baffa/src/ska/cheetah/cheetah/../cheetah/pipeline/detail/BeamLauncher.cpp:171][1600767420]Finished creating pipelines
[log][tid=140474636963584][/home/baffa/src/ska/cheetah/cheetah/../cheetah/pipeline/detail/BeamLauncher.cpp:223][1600767420]Starting Beam: identifier to distinguish between other similar type blocks
[log][tid=140474527926016][/home/baffa/src/ska/cheetah/cheetah/../cheetah/sps/detail/Sps.cpp:110][1600767420]setting dedispersion buffer size to 2048 spectra
[log][tid=140474527926016][/home/baffa/src/ska/cheetah/cheetah/../cheetah/sps/detail/Sps.cpp:113][1600767420]setting buffer overlap to 1514 spectra
[log][tid=140474527926016][/home/baffa/src/ska/cheetah/cheetah/sigproc/src/SigProcFileStream.cpp:334][1600767424]resizing to 1024
[log][tid=140474527926016][/usr/local/include/panda/detail/Pipeline.cpp:63][1600767424]End of stream
Cheetah pipeline is a stand alone CLI program with its main output on stdout. The obvious choice to handle from Python such a program is to use a subprocess.Popen class 1. We give here an example of its use:
- with p = subprocess.Popen([“./cheetah/pipeline/cheetah_pipeline”,”–config”,”cheetah.xml”, “-p”, “Dedispersion”, “–log-level”, “log”], stdout=PIPE) as proc:
printf(proc.stdout.read())
This command line approach makes Cheetah program completely deaf while running: it is not foreseen a communication channel from CONTROL to the pipeline. The only possible channel is the use of Posix signals. We list here few useful ones with default behaviour:
SIGKILL 9 Kill signal → Terminate
SIGTERM 15 Termination signal → Terminate
SIGUSR1 30,10,16 User-defined → Terminate
SIGSTOP 17,19,23 Stop process → Terminate
The use of SIGKILL, SIGTERM and SIGSTOP are clear and related to Abort (first and second) and to Stop (last). We have the opportunity to implement a custom channel by the use of SIGUSR1.
Advancement monitor¶
The CONTROL protocol requires to have the possibility to monitor, even in a coarse way, the pipeline advancement status. We proposed to add to the log channel an advancement message. But eve the simplest approach (the current step over the total number of steps of the required pipeline) is difficult to implement such an advancement approach. A possible workaround can be devise from the consideration that the processing time will be tuned to be slightly less than the [sub-]scan duration. We can take this value and use the ratio (time elapsed) / scan duration as base for a very rough evaluation of the advancement bar.