cosmocalc does basic cosmological calculations.

Matthew R. Becker, UChicago & Stanford/SLAC Copyright (c) 2013-2014, New BSD License

USE THIS CODE AT YOUR OWN RISK!

I have done some debugging, but I cannot promise that everything is correct. If you find any bugs, please let me know!

Matthew R. Becker
becker.mr [at] gmail [dot] com

You will need to install the GNU Scientific Library. Once you do that follow the instructions below.

C coders: You can compile static or shared libs. Also, if you look in examples/ you can see how to directly link the code.

Python Peeps: The entire C code has been wrapped by SWIG. To install, you should just be able to type

python setup.py install

This assumes of course that your GSL is in a reasonable spot. If not, you will have to modify setup.py to include the paths to the headers and compiled libraries for GSL. (You can see this with the /opt/local/lib options in the script already. Just add your paths here. Note that environment variables are not resolved by python for whatever reason, so things like $HOME/lib will have to be resolved by hand. If you know how to do this, let me know!)

Units: I use h-inverse units, with Mpc/h and Msun/h where needed. Also, I work with scale factor as opposed to redshift, so be careful.

C coders: See the example directory. Note that cosmoData is a global struct with the cosmological parameters. When you want to change them, you need to increment field cosmoData.cosmoNum.

Python Peeps: It works like this

import cosmocalc  
cd = {"om":0.3,"ob":0.045,"ol":0.7, \
      "ok":0.0,"h" :0.7,"s8":0.8,"ns":0.95, \
      "w0":-1.0,"wa":0.0}
cosmocalc.set_cosmology(cd)
print cosmocalc.comvdist(0.5)

The above code will print the comoving distance to scale factor = 0.5. Note that the cosmology is a global variable in C. Thus you can only have one cosmology working at a time. To set a new cosmology, simply change the dictionary and then call cosmocalc.set_cosmology().

The documentation is complete in the sense that in ipython, simply do this

>>> cosmocalc.comvdist?

to see what each function does.

So the C code internally typically computes a given quantity as a function of scale factor, k, or whatever, and then builds a spline. The splines are built on-the-fly as needed. Thus the first call to a given quantity is slower than subsequent calls.

There is a single global variable (cosmoData) for the cosmology and the splines are rebuilt when the field cosmoData.cosmoNum is changed. The python interface does this automatically, but it has to be done by hand in the C code.

The integrations are all done with various adaptive integrators in GSL. The details are not too important, except to say that the integrations are good to at least few percent (and a lot are much, much better).

Copyright (c) 2013-2014, Matthew R. Becker
All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: * Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. * Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. * Neither the name of the nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

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