Opened 2 years ago

Last modified 20 months ago

#963 new defect

fix stacked disk (qx,qy) test

Reported by: pkienzle Owned by:
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 20 months ago by butler

  • Milestone changed from SasView 4.2.0 to SasView 4.3.0
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