Tutorials

Running Tests

Included with TesseRACt are several example halo snapshots that can be used to run a variety of tests. The primary function that should be used for running tests is tesseract.tests.run_test(). This function will create the necessary files, perform the tessellation, and calculate the NFW parameters using different techniques. For example, to test traditional fitting against tessellation based concentration measurement on a c = 10 halo:

>>> tesseract.tests.run_test(c=10,nfwmeth=['fitting','voronoi'])

You can also decrease the resolution by some factor:

>>> tesseract.tests.run_test(c=10,nfwmeth=['fitting','voronoi'],decimate=10)

or change the shape of the halo:

>>> tesseract.tests.run_test(c=10,nfwmeth=['fitting','voronoi'],squishz=0.3)

Running Test Series

In addition to individual tests, you can also run a series of tests that vary one parameter at a time using tesseract.tests.run_series(). For example, to test how tessellation based measurement of concentration is affected by how prolate a c=50 halo is, run:

>>> tesseract.tests.run_series('prolate',c=50,nfwmeth='voronoi')

The specific ‘prolateness’ values tested can be specified by either a list of values:

>>> tesseract.tests.run_series('prolate',vlist=[0.3,0.4,0.5],c=50,nfwmeth='voronoi')

or a range and number.:

>>> tesseract.tests.run_series('prolate',vlim=(0.3,0.5),Nv=3,c=50,nfwmeth='voronoi')

Running TesseRACt On Your Data

If your data is in one of the formats currently supported by TesseRACt, measuring the concentration using tessellation is relatively simple.

Creating a Parameter File

First you will need to create a parameter file either by hand or using tesseract.voro.make_param().:

>>> parfile = '\full\path\to\parameter\file'
>>> tesseract.voro.make_param(parfile,**param)

where param contains all of the required keywords listed under tesseract.voro._paramlist. If you do not wish to transform or downsample your particles and the data does not have periodic boundary conditions, you can autofill many of the parameters using values from the provided example parameter file tesseract.voro._example_parfile.:

>>> tesseract.voro.make_param(parfile,basefile=tesseract.voro._example_parfile,**param)

In this case, the only parameters you will need to provide in param are

• FilePrefix: Prefix to add to file names.
• PositionFile: Full path to file containing the particle data.
• PositionFileFormat: An integer specifying what format the PositionFile

is in (See tesseract.io.read_snapshot() for a list of valid formats). * OutputDir: Full path to directory where files should be saved.

Running the Tessellation

To run the actual tessellation, use tesseract.voro.run() with the parameter file you created in the previous step.:

>>> tesseract.voro.run(parfile)

If you would like the output to be piped into a file rather than displayed, provide an output file:

>>> tesseract.voro.run(parfile,outfile='/path/to/output/file')

If the error code returned is not 0, this means that there was a problem with the tessellation. The most common reason for a failed tessellation is a problem with the input snapshot.

Calculating the NFW Parameters

Once the tessellation is successful, NFW parameters can be computed from the volumes using tesseract.voro.get_nfw():

>>> tesseract.voro.get_nfw(parfile,method='voronoi')

Similarly, for using traditional fitting:

>>> tesseract.voro.get_nfw(parfile,method='fitting')

or both:

>>> tesseract.voro.get_nfw(parfile,method=['voronoi','fitting'])

Creating Snapshots

If your data is in a format that is not currently supported by TesseRACt, fear not! The tesseract.io module provides utilities for writing your data to a format that is supported. Simply load the masses and positions for your particles as numpy arrays and call tesseract.io.write_snapshot():

>>> print type(mass), mass.shape
(<type 'numpy.ndarray'>, (N,))
>>> print type(pos), pos.shape
(<type 'numpy.ndarray'>, (N,3))
>>> filename = '\path\to\new\snapshot.dat'
>>> format = 0 # This is a binary file containing just masses and positions
>>> tesseract.io.write_snapshot(filename,mass,pos,format=format)

Then just set ‘PositionFile’ and ‘PositionFileFormat’ to the new file name and format in your parameter file from above.