Accuracy of nfft
I have investigated the accuracy of our nfft implementation for 1 and for 100 data points:
Current implementation
1 data point
100 data points
Alternative
We use the following criterion to decide on the oversampling factor:
rat = 3 if eps < 1e-11 else 2
If one always takes an oversampling factor of 2 we arrive at the following results
1 data point
100 data points
Therefore, my suggestion is to drop oversampling with a factor of three since it does not add relevant accuracy.
Here is the original paper for the code. Chapter 4 describes the algorithm which we use. nufft_paper.pdf
This is the code which produces the plots. gridding_accuracy.py