What are some alternatives to a bit array?

Question

I have an information retrieval application that creates bit arrays on the order of 10s of million bits. The number of \"set\" bits in the array varies widely, from all clear to

Answer 1

Straight forward lossless compression is the way to go. To make it searchable you will have to compress relatively small blocks and create an index into an array of the blocks. This index can contain the bit offset of the starting bit in each block.