Stop col_norm early for < max hamming distance #154
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nonhermitian
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When doing large numbers of bit-strings, e.g. 100k or more, the column norm calculation can take a while. This can be minimized by doing the computation in parallel using the OPENMP capabilities in M3. However, there is some additional efficiency gains to be had when an user decides to truncate based on Hamming distance.
Here we compute the number of elements within a given Hamming distance, and stop if we have evaluated that number of elements. This gives a good speed up if the Hamming distance is small.
In principle, this could also be done in the iterative matvec code, but I did not observe a speed up when I tried, so will follow up with another PR if that indeed pans out.