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Get random element from set

See original GitHub issue

What’s the most efficient way to implement something like RoaringBitmap.random()?

For example, RoaringBitmap.first() and RoaringBitmap.last() return the smallest and largest elements… but how would you obtain a random element?

Thanks in advance!

Issue Analytics

State:
Created 6 years ago
Comments:19 (10 by maintainers)

Top GitHub Comments

2reactions

blacellecommented, Sep 13, 2017

What about

Random random = new Random();
bitmap.select(random.nextInt(this.getCardinality()));

1reaction

lemirecommented, Sep 20, 2017

If you have a random pool, it is not going to be efficient to represent it solely as ranges, like you did. I think that the reason the ranges are efficient, is because of the strong statistical bias you have introduced.

That is, the minute you get close to a half empty interval, if you picked the elements at random, a set of ranges won’t be close to optimal storage-wise.

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