CAMB: transfer_k_per_logint (possible bug?)
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- Posts: 24
- Joined: February 05 2005
- Affiliation: University of Portsmouth
CAMB: transfer_k_per_logint (possible bug?)
Hi All,
I find that when I run CAMB (September 06) with transfer\_k\_per\_logint = 0 or 5, I get more than just different k-sampling - I get differences in the transfer function and matter power spectrum. The latter changes up to 3 percent near k=0.1h/Mpc (i.e. the baryon wiggles) with the settings I'm using. Is this a bug? Expected? My fault?
Here is my base parameter file
Here I plot the fractional difference in the linear power spectrum.
Here I vary Omega_K (curvature) by 0.02 and plot the fractional difference in the linear power spectrum for both samplings.
Chaz
I find that when I run CAMB (September 06) with transfer\_k\_per\_logint = 0 or 5, I get more than just different k-sampling - I get differences in the transfer function and matter power spectrum. The latter changes up to 3 percent near k=0.1h/Mpc (i.e. the baryon wiggles) with the settings I'm using. Is this a bug? Expected? My fault?
Here is my base parameter file
Here I plot the fractional difference in the linear power spectrum.
Here I vary Omega_K (curvature) by 0.02 and plot the fractional difference in the linear power spectrum for both samplings.
Chaz
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- Posts: 1941
- Joined: September 23 2004
- Affiliation: University of Sussex
- Contact:
Re: CAMB: transfer_k_per_logint (possible bug?)
If you set
transfer_high_precision = T
the errors should be below \alt 0.5%.
transfer_high_precision = T
the errors should be below \alt 0.5%.
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- Posts: 24
- Joined: February 05 2005
- Affiliation: University of Portsmouth
CAMB: transfer_k_per_logint (possible bug?)
Setting transfer_high_precision = T, I am still seeing a fractional difference of 3\% in the power spectrum for the two sampling methods.
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- Posts: 1941
- Joined: September 23 2004
- Affiliation: University of Sussex
- Contact:
Re: CAMB: transfer_k_per_logint (possible bug?)
But I think the adaptive transfer_k_per_logint = 0 is correct? Compared to transfer_k_per_logint = 15 I have ~ 0.3% max error: transfer_k_per_logint = 5 is just a fixed spacing which may not be good enough to sample the baryon oscillations very well.
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- Posts: 24
- Joined: February 05 2005
- Affiliation: University of Portsmouth
CAMB: transfer_k_per_logint (possible bug?)
Yes - now I see. I was confused why the results should differ at identical wavenumbers... but since some splines are involved, the sampling would affect the accuracy. Thanks, Antony.
Chaz
Chaz