From: Brian Candler Date: 2012-05-24T01:00:38+09:00 Subject: Re: Memory-efficient set of Fixnums Can you afford a fixed 512MB of RAM? Then you can just have a 2^32 entry bitmap (2^29 bytes) Iteration might be fast enough, you just need to search for bytes which are not \x00 -- Posted via http://www.ruby-forum.com/.