Opened 20 months ago
Last modified 15 months ago
#963 new defect
fix stacked disk (qx,qy) test
Reported by: | pkienzle | Owned by: | |
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Priority: | major | Milestone: | SasView 4.3.0 |
Component: | SasView | Keywords: | |
Cc: | Work Package: | SasView Bug Fixing |
Description
The tests in stacked disk fail for single precision because J1(qr) is not accurate for large qr. In this test, radius=3000.
Use the following to see the error as a function of q for large radius:
explore/precision.py cylinder
We are using cephes for our implementation of J1. The implementation in fnlib did not perform any better. Note that precision.py shows single precision J1 in numpy/scipy to be more accurate, but that is probably because it is using double precision internally.
The following paper provides an alternative algorithm:
http://ieeexplore.ieee.org/iel5/5223291/5223292/05223347.pdf
Harrison, J., 2009. Fast and accurate Bessel function computation, in: Computer Arithmetic, 2009. ARITH 2009. 19th IEEE Symposium On. IEEE, pp. 104–113.
Change History (1)
comment:1 Changed 15 months ago by butler
- Milestone changed from SasView 4.2.0 to SasView 4.3.0