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LSSTDESC / firecrown

DESC Cosmology Likelihood Framework
BSD 3-Clause "New" or "Revised" License
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A_s vs sigma_8 #244

Closed elisachisari closed 1 year ago

elisachisari commented 1 year ago

In the cosmicshear example, within cosmicshear_values.ini, it seems both sigma_8 and A_s are being fixed. How does it work in the current implementation? Only one should be necessary, so why are both specified?

elisachisari commented 1 year ago

Also, in the .ini file, what does sigma8_rescale do?

joezuntz commented 1 year ago

That appears to be left over from an earlier version of cosmosis. In a previous version camb was always run with an initial placeholder A_s and then rescaled afterwards by that module. In more recent versions the sigma8_rescale module and A_s parameter can be removed, as (thanks to Jessie Muir) the camb interface now does that internally.

marcpaterno commented 1 year ago

I have tried removing A_s from cosmicshear_values.ini and sigma8_rescale from cosmicshear.ini. But this causes a failure. The problem occurs in camb_interface.py on line 257 (I am at commit d7a2052d21fa308f39d6f5675a553c6e153c167e in the CosmoSIS standard library). This line is in the function extract_initial_power_params; it is looking up a value of A_s in the datablock.

In case it matters, the version of CosmoSIS in my environment is 2.3. It was installed using conda, and the CSL was built using cosmosis-build-standard-library version 1.2

joezuntz commented 1 year ago

You also need to rename the parameter to sigma_8_input (added underscore).