CAMB: accuracy boosts
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- Posts: 54
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- Affiliation: University College London
CAMB: accuracy boosts
Hello,
To what should I set the accuracy parameters in CAMB in order to get the same level of accuracy as, for example, the CMBFAST high-precision option? [accuracy_boost, l_accuracy_boost, l_sample_boost etc].
Thanks!
Hiranya
To what should I set the accuracy parameters in CAMB in order to get the same level of accuracy as, for example, the CMBFAST high-precision option? [accuracy_boost, l_accuracy_boost, l_sample_boost etc].
Thanks!
Hiranya
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- Posts: 1941
- Joined: September 23 2004
- Affiliation: University of Sussex
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CAMB: accuracy boosts
accuracy_boost=2
l_accuracy_boost=2
should be better than CMBFAST with HP. You may also want to try higher l_sample_boost, but I don't think CMBFAST's HP option decreases the l sampling. The lower-l polarization is quite sensitive to the l sampling, which may explain differences you see with CMBFAST at l < 200.
l_accuracy_boost=2
should be better than CMBFAST with HP. You may also want to try higher l_sample_boost, but I don't think CMBFAST's HP option decreases the l sampling. The lower-l polarization is quite sensitive to the l sampling, which may explain differences you see with CMBFAST at l < 200.
Last edited by Antony Lewis on April 11 2005, edited 5 times in total.
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- Posts: 54
- Joined: September 28 2004
- Affiliation: University College London
CAMB: accuracy boosts
Thanks. I have to say I am amazed at the time difference between the codes. I just ran them on a dual 2.5 GHz Apple G5 with the IBM XLC 95 compiler. CAMB with the accuracy parameters you suggested took 5.992s. CMBFAST *without* the HP option took 19.594s. I did not expect such a huge factor in the speed. I wonder if its because the f77 code is not optimizing as well.
Do you have any ideas about how the two codes benchmark? Is what I found reasonable?
Hiranya
Do you have any ideas about how the two codes benchmark? Is what I found reasonable?
Hiranya
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- Posts: 1941
- Joined: September 23 2004
- Affiliation: University of Sussex
- Contact:
CAMB: accuracy boosts
I've not tried systematically benchmarking them, but what you get doesn't sound too unreasonable. I think CMBFAST slowed down a bit quite recently when they improved its accuracy, when at the same time CAMB sped up due to (amongst other things) using the higher order terms in the tight-coupling expansion. CAMB has always been a lot faster for non-flat models.
CAMB will be significantly slower if you run with lensing, massive neutrinos or including the transfer functions, but probably CMBFAST will be too.
CAMB will be significantly slower if you run with lensing, massive neutrinos or including the transfer functions, but probably CMBFAST will be too.