0b98d78664
In meituan, pr #6625 was revert due to the oom probleam. currently, we are trying to modify the old hyperloglog, based on pr #8555, we did some works. via some test, we find it better than old hll, and better than apache:master hll. Changes summary: - use SIMD max tp speed up heavy function _merge_registers - use phmap::flat_hash_set rather than std::set - replace std::max - other small changes