is there an advantage to using the constant for END and REP rather than 0 and 1?

Beyond a little extra clarity, no. I did it to make the two versions visibly comparible.

There might be some extra memory savings to be had if you could give a clearer idea of the numbers involved.

Ie. How many chromosomes? Approximate maximum lengths of both the chromosomes and the ranges?

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.

In reply to Re^3: Reducing memory footprint when doing a lookup of millions of coordinates by BrowserUk
in thread Reducing memory footprint when doing a lookup of millions of coordinates by richardwfrancis

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