taskGNU Astronomy Utilities - Tasks: task #14665, Cosmological functions in library

 
 

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task #14665: Cosmological functions in library

Submitter:  Mohammad Akhlaghi <makhlaghi>
Submitted:  Fri 29 Sep 2017 11:52:31 AM UTC
   
 
Should Start On:  Thu 28 Sep 2017 10:00:00 PM UTC Should be Finished on:  Thu 28 Sep 2017 10:00:00 PM UTC
Category:  Libraries Priority:  5 - Normal
Item Group:  Enhancement Status:  Done
Privacy:  Public Assigned to:  makhlaghi
Percent Complete:  100% Open/Closed:  Closed
Effort:  0.00

Tue 03 Oct 2017 02:56:03 PM UTC, comment #2: 

This task has been completed and pushed to the main repo.

The cosmology calculation functions are now moved to the library and thus more generically usable. The CosmicCalculator program now calls the library functions for its results.

The issue on speed that was raised by Boud is moved to task 14689.

Mohammad Akhlaghi <makhlaghi>
Group administrator
Tue 03 Oct 2017 02:33:17 AM UTC, comment #1: 

See https://bitbucket.org/broukema/gnuastro/branch/cosmo-dev
for a proof-of-concept of a 100x speed up for Universe ages.
It's a bit hacked but enough to get started on
improving the cosmo functions, I think.

I get the output from commit dd4443a :

ageofuniverse benchmark: old 1.81705  new 0.013959, old/new 130.17
0.815234


I don't think we'll get much of a speed-up in proper distances
compared to https://arxiv.org/abs/1702.0886 (ignore the comments
there about luminosity distance being the main distance; it's
main in terms of observational analysis, but proper distance
is simpler in terms of the FLRW models.)

We would need an analytical integral of (sinh x)^(-2/3), because
d_{radial_comoving} = \int c dt/a(t) - see
http://ned.ipac.caltech.edu/level5/March02/Sahni/Sahni3_2.html

The best that https://en.wikipedia.org/wiki/List_of_integrals_of_hyperbolic_functions suggests
would be to rewrite it in terms of \int (sinh x)^(4/3) , which
wouldn't help much. :P

We can implement what looks best for proper distances after re-reading 1702.0886.

The non-flat cases should be added too.

Boud Roukema <boud>
Group Member
Fri 29 Sep 2017 11:52:31 AM UTC, original submission:  

Gnuastro's (currently small) set of cosmology functions are now limited to the CosmicCalculator program.

To be more generally useful, it would be much better if these functions were moved to the library. CosmicCalculator can then simply call the library functions for its calculations.

Mohammad Akhlaghi <makhlaghi>
Group administrator

 

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