Adding a pure python truncated octahedron model with Fibonacci orientation averaging #738
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| using the Fibonacci quadrature. This quadrature provides a quasi-uniform distribution of points on the unit sphere | ||
| using the golden ratio. The only new parameter is the number of points to generate on the unit sphere. | ||
| The default value (around 400 points) provides a good balance between accuracy and computational efficiency. | ||
| It contains both the form factor for a reference orientation and the 1D form factor after orientation average (Gauss-Legendre). |
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Since it's using the fibonacci quadrature, shouldn't we keep the fibonacci description in the documentation instead of Gauss-Legendre ?
states at the beginning that this is a pure python version using Fibonacci integration.
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This version (pure python plus FIbonacci integration) is useful for comparision purposes with the truncated_octahedron model which is based on .c and .py with adaptive Gauss-Legendre integration.
Here (truncated_octahedron_fibonacci) all analytical expressions are coded in python (no .c file).
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Description
Adding a pure python model for truncated octahedrons with orientation averaging using Fibonacci quadrature.
Fixes #686
Replaces #694
How Has This Been Tested?
Unit tests worked.
This model was compared with the model using C code (octahedron_truncated.c) and shows good agreement.
In general, the octahedron model was compared to an another numerical calculation : for truncated octahedrons with different sizes and truncatures, agreement was found with the Debye equation (Debye calculator: https://github.com/FrederikLizakJohansen/DebyeCalculator). The Debye equation is based on atomic positions while SasView model is based on analytical expressions.
More tests should be made on small q. Indeed, like the previous model (octahedron_truncated.c), we encouter issues when it comes to small q (q<10^-6 Angs). More precise mathematical should be used (hospital rule, etc).
Note : the fibonacci quadrature code (sasmodels/quadratures/fibonacci.py) was added to a new repository called "quadratures" because it could be also useful for other models.
Compare with gauss-legendre grid using:
Parameters set on the command line (e.g.
radius_a=1000) will be shared between the two models.Adjust the number of fibonacci points using
npoints_fibonacci=n. Adjust the number of gaussian quadrature points using-ngauss=n(where n is zero for adaptive integration).Review Checklist:
[if using the editor, use
[x]in place of[ ]to check a box]Documentation (check at least one)
Installers
Licensing (untick if necessary)