You don't seem to have a public repository for the code described in your posts (presumably a part of Chessbook?), but you might be using a textbook arithmetic

You don't seem to have a public repository for the code described in your posts (presumably a part of Chessbook?), but you might be using a textbook arithmetic coding algorithm which maintains both lower and upper bounds and does a renormalization by comparing topmost bits. If it's the case rANS would be much simpler to write and more efficient [1]. If your AC code is already well-optimized, there is not much reason to switch though. [1] Fabian Giesen's sample implementation is already as good as is, and also contains a good alias table implementation if you want multi-symbol inputs: https://github.com/rygorous/ryg_rans/blob/master/rans_byte.h https://github.com/rygorous/ryg_rans/blob/master/rans_byte.h