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This provides a simple regular histogram with the bist.nim interface, but using vanilla bin counters mostly so it can be used with adix/xhist1. Bin incs are fast & adix/cumsum can be at least tolerable via parallel prefix sum on x86_64. Re-scaling|shifting bins can also be done (externally) post-decrement & pre-increment and is very vectorizable. This enables general weight decay, not only exponential/linear/flat, but adds per-point expense proportional to nBin. For specific weight decays this could be ~2X optimized some by "always counting up", as with Fenwick-backed embist/lmbist, but we hold off on that for now to provide a distinct calculation with distinct FP math trade offs.

Performance break-even vs BIST methods depends on (at least!) counter size / vectorization, platform, time kernel, and work load. Ballpark expectations might be to use this <= ~300 bins for 1:1 ratios of dec, inc & quantile with this being about 4X faster for 8 bins & nBin/lg(nBin) slower for larger nBin. This can be strictly faster if your use case has many counter updates per quantile query. This can also potentially be accelerated by GPUs (especially in the context of transforming whole, already existing arrays rather than online / incremental transformation). The bottom of this module has a small test/timing program against a bist.