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Table 1

Estimation of Fourier-Bessel coefficients: comparison of the new method, the reverse formulation (Eqs. (19) and (20) using HEALPix discretisation) with the original, raw formulation (Eq. (7)).

N nside ϵr(fℓmn) < 0.3% ϵr(Cℓn) < 0.3% T
[0, 20]/[21, 50] [0, 20]/[21, 50]

4.2e5 512 87%/42% 99%/96% 8
1024 95%/65% 99%/98% 4
2048 99%/84% 99%/99% 2
3.1e6 512 92%/50% 99%/95% 10
1024 98%/74% 100%/100% 5
2048 99%/90% 100%/100% 2
9.7e6 512 92%/50% 100%/97% 12
1024 97%/74% 100%/100% 6
2048 99%/90% 100%/100% 3

Notes. The third (fourth) column gives the percentage f coefficients for which the relative accuracy ϵ(fℓmn) (ϵ(Cℓn)) is lower than 0.3% for given values of nside and N. T is the ratio of elapsed times of the two methods.

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