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cmodel (Model Image Generator) — CentralProcessor 0.11 documentation

cmodel (Model Image Generator)ТЖ

The cmodel pipeline task is responsible for extracting a local sky model (LSM) from the global sky model (GSM) and building an image from the components and/or images resulting from the request.

The cmodel program only supports the construction of continuum images, however it does support taylor terms allowing the modeling of spectral index and curvature.

Running the programТЖ

It can be run with the following command, where “config.in” is a file containing the configuration parameters described in the next section.

$ <MPI wrapper> cmodel -c config.in

Parallel/Distributed ExecutionТЖ

The program is distributed and used a master/worker pattern to distribute and manage work. Each worker receives a subset of the components to image. Components are allocated to the workers in small batches, and only when the worker is finished with one batch is another batch allocated to it. This provides a reasonable approach to load-balancing. Once all components have been imaged the images are reduced back to the master and a single image file is written to disk.

The program requires at least to processes to execute, and failure to either execute cmodel as an MPI process or specifying only one MPI process will result in the following error:

Execution requires at least 2 MPI processes (thrown in apps/cmodel.cc:66)

On the Cray XC30 platform executing with the MPI wrapper takes the form:

$ aprun -n 40 -N 20 cmodel -c config.in

The -n and -N parameters to the aprun application launcher specify 40 MPI processes will be used (39 workers and one master) and each node will host 20 MPI processes. This job then requires two compute nodes.

Configuration ParametersТЖ

Parameter Default Example Description
Cmodel.gsm.database None dataservice Either “dataservice”, “votable” or “asciitable”.See below for additional related options
Cmodel.gsm.ref_freq None 1.4GHz The reference frequency for the base flux quantity stored in the GSM. Note: Eventually this will just be obtained from the Sky Model Service.
Cmodel.bunit None Jy/pixel  
Cmodel.frequency None 1.420GHz Frequency
Cmodel.increment None 304MHz Bandwidth
Cmodel.flux_limit None 10uJy Lower limit on flux. Only sources of equal of greater flux will be imaged.
Cmodel.shape None [5120, 5120] Output image dimensions
Cmodel.cellsize None [5arcsec, 5arcsec] Cell size (angular size for each pixel)
Cmodel.direction None [12h30m00.00, -45.00.00.00, J2000] Image center. Must be J2000
Cmodel.stokes [I] [I,Q,U,V] Stokes parameters in the output image.
Cmodel.output casa casa Currently only support casa output
Cmodel.filename None image_10uJy.skymodel Name of image file created
Cmodel.batchsize 100 100 Number of components to send worker when worker requests more work.
Cmodel.nterms 1 1 Number of taylor term images to produce. Valid inputs are 1, 2 and 3.

If Cmodel.gsm.database is set to dataservice then the Sky Model Data Service is used as the global sky model source. In this case the following three options are used.

Parameter Default Example Description
Cmodel.gsm.locator_host None localhost Host or IP address of the ICE locator service
Cmodel.gsm.locator_port None 4061 IP port the ICE locator service is listening on
Cmodel.gsm.service_name None SkyModelService Identity of the sky model service in the ICE locator service (registry)

If Cmodel.gsm.database is set to votable then a VOTable is used as the global sky model source. In this case the following option is used to specify the name of the file to read in.

Parameter Default Example Description
Cmodel.gsm.file None inputfile.xml File to read

If Cmodel.gsm.database is set to asciitable then a row/column (space separated) file is used as the global sky model source. In this case the following option is used to specify the name of the file to read in.

Parameter Default Example Description
Cmodel.tablespec.ra.col None 3 Column (zero based) containing the RA
Cmodel.tablespec.ra.units None deg RA units (Must confirm to degrees)
Cmodel.tablespec.dec.col None 4 Column (zero based) containing the Declination
Cmodel.tablespec.dec.units None deg Declination units (Must confirm to degrees)
Cmodel.tablespec.flux.col None 10 Column (zero based) containing the flux
Cmodel.tablespec.flux.units None Jy Flux units (Must conform to Jy)
Cmodel.tablespec.majoraxis.col None 6 Column (zero based) containing the major axis
Cmodel.tablespec.majoraxis.units None arcsec Major axis units (must confirm to degrees)
Cmodel.tablespec.minoraxis.col None 7 Column (zero based) containing the minor axis
Cmodel.tablespec.minoraxis.units None arcsec Major axis units (must conform to degrees)
Cmodel.tablespec.posangle.col None 5 Column (zero based) containing the position angle
Cmodel.tablespec.posangle.units None rad Position angle units (must confirm to degrees)
Cmodel.tablespec.spectralindex.col None 12 Column (zero based) containing the spectral index
Cmodel.tablespec.spectralcurvature.col None 13 Column (zero based) containing the spectral curvature

Note: Neither spectral index or curvature require units.

Configuration ExampleТЖ

Example 1ТЖ

This first example demonstrates configuration using the Sky Model Data Service as the global sky model source.

# The below specifies the GSM source is the Sky Model Service
Cmodel.gsm.database       = dataservice
Cmodel.gsm.locator_host   = localhost
Cmodel.gsm.locator_port   = 4061
Cmodel.gsm.service_name   = SkyModelService
Cmodel.gsm.ref_freq       = 1.4GHz

# General parameters
Cmodel.bunit              = Jy/pixel
Cmodel.frequency          = 1.420GHz
Cmodel.increment          = 304MHz
Cmodel.flux_limit         = 10uJy
Cmodel.shape              = [5120, 5120]
Cmodel.cellsize           = [5arcsec, 5arcsec]
Cmodel.direction          = [12h30m00.00, -45.00.00.00, J2000]
Cmodel.stokes             = [I]
Cmodel.nterms             = 3

# Output specific parameters
Cmodel.output             = casa
Cmodel.filename           = image_10uJy.skymodel

Example 2ТЖ

This second example demonstrates configuration using an output file from the VOTable source finder as the global sky model source.

# The below specifies the GSM source is a duchamp output file
Cmodel.gsm.database       = votable
Cmodel.gsm.file           = duchamp-fitResults.xml
Cmodel.gsm.ref_freq       = 1.421GHz

# General parameters
Cmodel.bunit              = Jy/pixel
Cmodel.frequency          = 1.420GHz
Cmodel.increment          = 304MHz
Cmodel.flux_limit         = 10mJy
Cmodel.shape              = [4096, 4096]
Cmodel.cellsize           = [5arcsec, 5arcsec]
Cmodel.direction          = [12h30m00.00, -45.00.00.00, J2000]
Cmodel.stokes             = [I]
Cmodel.nterms             = 3

# Output specific parameters
Cmodel.output             = casa
Cmodel.filename           = image_10mJy.skymodel