Enable Count-Filtered SetSketch for the case that a and b are set before sketching.
Use more precision to format the a and b variables. Uses at most 16 digits of precision. Previous std::to_string would truncate to 6 digits, which was not useful.
This pull request fixes 3 alerts when merging c308b12cfb4f9a35b3b0e8d2fa643dfca855bb3b into b79f67e5b04bacd41f7840f1974638ca0a789a3d - view on LGTM.com