Baryons objects as convenience input for Cosmology

[damonge]

This implements, as discussed in the last CCL telecon, the possibility to pass baryonic effects objects as part of the cosmology initialisation. This is a convenience feature, so users can just keep using Cosmology objects as containers for the non-linear matter power spectrum, which now can include baryonic effects.

[coveralls]

Pull Request Test Coverage Report for Build 5694186616

• 7 of 7 (100.0%) changed or added relevant lines in 1 file are covered.
• 12 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.004%) to 97.446%

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Files with Coverage Reduction	New Missed Lines	%
pyccl/cosmology.py	1	99.49%
pyccl/boltzmann.py	11	95.32%

Totals
Change from base Build 5625195580:	0.004%
Covered Lines:	5685
Relevant Lines:	5834

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💛 - Coveralls

[elisachisari]

Working well for me. Some small suggestions.
I don't see files for the docs except the cosmicemu one - did you recompile the docs?

[damonge]

@elisachisari @tilmantroester back to you. I think the main question mark is whether we keep "bcm" as a convenient option or just remove it completely (since it's not much harder than passing ccl.baryons.BaryonsSchneider15().

[marcpaterno]

While I’m somewhat late to the game, I think having a default-initialized ccl.baryons.BaryonsSchneider15 object is clearer than having a string with a special value in the interface is clearer, and easier to search for with tools like an IDE or even grep.

[damonge]

Thanks @marcpaterno , but to be clear, the default here will be None (meaning no baryonic effects correction)

[tilmantroester]

This might be a more general idea than what's covered in this PR but would it make sense to allow the baryons object to be more general than the baryons.Baryons API? What I have in mind is having something like a HMCode2020Params class that could be passed to the baryons argument to Cosmology and which internally sets the extra_parameters that get passed to CAMB. This HMCode2020Params wouldn't have the include_baryonic_effects API but would allow a consistent use of the Cosmology API for HMCode2020 baryons.

[elisachisari]

If we remove the 'bcm' option I think we are then done.

[damonge]

OK, thanks all. The proposal is then:
a) the default value of baryonic_effects is None, which means "do not apply any baryonic effects".
b) the only other option is a Baryons object. No 'bcm' option (users need to instantiate the corresponding Schneider15 class).

All happy?

[marcpaterno]

I like this solution.

[damonge]

Alright, done!