Comparing relative error between current and old CAMB version
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- Posts: 11
- Joined: March 27 2019
- Affiliation: University of Texas at Dallas
Comparing relative error between current and old CAMB version
Hello,
I would like to compare the relative error between the current camb version and an old version in for example, CMB or matter power spectra. However, when I set the values of the cosmological parameters (H0, ombh2, etc...), it seems to me that these versions output a different results for quantities such as Om_Lambda, 100*theta, etc... Then, I am not comparing exactly the same model. So, is there a easy way to set exactly the same values by changing some settings in params.ini or this issue is unavoidable with the new modifications?
Best regards,
Cristhian Garcia.
I would like to compare the relative error between the current camb version and an old version in for example, CMB or matter power spectra. However, when I set the values of the cosmological parameters (H0, ombh2, etc...), it seems to me that these versions output a different results for quantities such as Om_Lambda, 100*theta, etc... Then, I am not comparing exactly the same model. So, is there a easy way to set exactly the same values by changing some settings in params.ini or this issue is unavoidable with the new modifications?
Best regards,
Cristhian Garcia.
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- Posts: 1943
- Joined: September 23 2004
- Affiliation: University of Sussex
- Contact:
Re: Comparing relative error between current and old CAMB version
If you set parameters consistently they should agree well for background quantities (down to 1e-4 level. where it matters for example whether or not you include the photon density when working out $\Omega_\Lambda$). Check things like the Helium density and neutrino model are the same.
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- Posts: 11
- Joined: March 27 2019
- Affiliation: University of Texas at Dallas
Re: Comparing relative error between current and old CAMB version
Hello A. Lewis,
Just going back to this issue, I run camb by using the current version of CosmoMC which is in the github (I called CosmoMC-2020) and also run camb with the version of CosmoMC called CosmoMC-Planck2018.
Then, I set the background quantities and as you said, they agree well within 1e-4. However, I can see that by using the default settings, both version of cosmomc give a relative error of around 1e-3 for C^{TT}_{ell}. For the other C'ells I can reduce the relative error by changing the accuracy settings, however for TT I cannot, is this contemplated after updating the previous version? or did I make some omission?
I attach two plots (the TT I am talking about and the comparison of the P(k) which agreed very nicely).
https://drive.google.com/open?id=15t0O7VSmIeR4_gciseSpp57iG-ZUJMov
https://drive.google.com/open?id=1WwaY5id-mUtDVNt1cjZFUHunVoDrFVBr
Best regards,
Cristhian Garcia.
Just going back to this issue, I run camb by using the current version of CosmoMC which is in the github (I called CosmoMC-2020) and also run camb with the version of CosmoMC called CosmoMC-Planck2018.
Then, I set the background quantities and as you said, they agree well within 1e-4. However, I can see that by using the default settings, both version of cosmomc give a relative error of around 1e-3 for C^{TT}_{ell}. For the other C'ells I can reduce the relative error by changing the accuracy settings, however for TT I cannot, is this contemplated after updating the previous version? or did I make some omission?
I attach two plots (the TT I am talking about and the comparison of the P(k) which agreed very nicely).
https://drive.google.com/open?id=15t0O7VSmIeR4_gciseSpp57iG-ZUJMov
https://drive.google.com/open?id=1WwaY5id-mUtDVNt1cjZFUHunVoDrFVBr
Best regards,
Cristhian Garcia.
-
- Posts: 1943
- Joined: September 23 2004
- Affiliation: University of Sussex
- Contact:
Re: Comparing relative error between current and old CAMB version
There will be some numerical changes due to CAMB updates, what you plot looks fine - on small scales the difference is well below 0.1% (on large scales 0.1% is fine because the cosmic variance is large).
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- Posts: 11
- Joined: March 27 2019
- Affiliation: University of Texas at Dallas
Re: Comparing relative error between current and old CAMB version
Hello Anthony,
thank you! you explanation makes sense actually.
Best regards,
Cristhian Garcia.
thank you! you explanation makes sense actually.
Best regards,
Cristhian Garcia.