[ET Trac] #2413: Include "POWER" code to extrapolate waveforms to scri+ into ET

[Gabriele Bozzola]

#2413: Include "POWER" code to extrapolate waveforms to scri+ into ET

 Reporter: Roland Haas
   Status: open
Milestone: 
  Version: 
     Type: task
 Priority: major
Component: EinsteinToolkit thorn

Comment (by Gabriele Bozzola):

What I had in mind is that one can put `power.py` in their PATH and use it for all their simulations without having to touch the code. This requires the parameters to be adjustable via command-line. But if that is not the designed way of using the tool, that would be fine.

Also, for clarity, instead of defining a string `FROM_TWOPUNCTURES` that is going to be compared to something that is morally a float \(`f0` and `ADMMass`\), I would recommend setting the default of two parameters to `None` in the function definitions, and then checking if value is `None`. If not, one can assume that the values from TwoPunctures are used \(which is what is happening now\). So, something along the lines of

```python
if f0 is None:
  f0 = getCutoffFrequencyFromTwoPuncturesBBH(meta_name)
```

\(As someone that is not familiar with the code, I found the `FROM_TWOPUNCTURES` variable very confusing, but maybe its role will be clarified by the documentation.\)

Two additional comments are:

* When the spin is computed from QLM a specific column is read. In my simulation, column 59 corresponds to `59:qlm_coordspinx[1]`, which is not the mass. Some assumptions are being made here and no checks are performed. This might lead to subtly wrong results.
* It would be nice, and probably easy, to extend POWER to be able to compute the strain at a fixed radius \(essentially, only doing the FFI\).  My use case is this. I tried POWER on my data and the output doesn’t look good at all. I don’t know if the problem is the interpolation to infinity or the data. Maybe the data becomes unreliable at a specific distance. If I can plot the strains at all the various distances I can get a sense of what is going on. 

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Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2413/include-power-code-to-extrapolate
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