Add benchmarks from unyt paper (Goldbaum 2018)

[pllim]

Fix #53. xref astropy/astropy#7546 and astropy/astropy#7549

[ngoldbaum]

This is probably a separate issue, but don't astropy's benchmarks use airspeed velocity? The last time I checked asv doesn't have a way to control CPU throttling or other effects that might introduce benchmark variance. You may want to consider integrating perf into your airspeed velocity setup to reduce issues like that.

[pllim]

You may want to consider integrating perf into your airspeed velocity setup

Perhaps @astrofrog can comment on this. Locally, I run it on a single core on my machine but I don't know my OS does throttling or not. I think we see small scale variations but overall trend is reliable. Ref: http://www.astropy.org/astropy-benchmarks/

(Yes, it is a separate issue. This PR simply introduces new benchmarks according to your paper.)

[astrofrog]

@ngoldbaum:

This is probably a separate issue, but don't astropy's benchmarks use airspeed velocity? The last time I checked asv doesn't have a way to control CPU throttling or other effects that might introduce benchmark variance

When running asv, we only run it on physical machines (not using CI) and prevent core-swapping using taskset -c 0 asv so we get reasonably stable results:

http://www.astropy.org/astropy-benchmarks/#coordinates.time_latitude

[pllim]

@mhvk and @ngoldbaum , I think I addressed all your comments.

@astrofrog , I ran the benchmarks and results should be in https://github.com/pllim/astropy-benchmarks/tree/lim-test but I am having trouble getting them to show up in https://pllim.github.io/astropy-benchmarks/ . I think it is the same problem as #50 but I am not sure where is the script that you updated for the fix.

[pllim]

Update: Turns out I needed to also copy results/benchmarks.json over to "results" branch, not just results/machine_name/ folder. New benchmarks (for limited number of commits) appear at https://pllim.github.io/astropy-benchmarks , so subclassing seems to work!