New method for computing optical depths #93
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…ork too. Superlinear power laws for temperature seem to result in a minor offset compared to the default feautrier solver, but in that case I do not know which is more accurate.
…is obtained. Furthermore tried to write own specialized version of erf, but the compiler wins.
…tau methods should still be implemented properly TODO.
This was referenced Jul 15, 2022
…ute the optical depth.
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Implemented a new way of computing the optical depth by integrating the opacity over an individual line. This changes the way how rays need to be handled (no longer do we need to add ghost points in between if the doppler shift is too large). For models with moderate shifts, this can be about 10% slower, however, for larger doppler shifts, this results in a massive performance increase (no longer does the computation time scale with the total shift on the ray). On the plus side, the optical depth should be computed more accurately. For playing around with speed vs accuracy, one can always change the parameter max_width_fraction (higher->less accurate, but faster).
Practically, most solvers just have some minor code changed to use the new method. However, the short-characteristics method has been (lazily) rewritten to use the source function and optical depth instead of emissivity and opacity. The inspection function for the feautrier solver has also been slightly changed and now no longer returns the emissivity and opacity (instead return the source function).