For 64-bit x86 code, on long strings, the picture is more complicated. On many recent Intel CPUs, such as Nehalem, Westmere, Sandy Bridge, etc., CityHashCrc128 appears to be faster than all competitors of comparable quality. CityHash128 is also good but not quite as fast. We believe our nearest competitor is Bob Jenkins' Spooky. We don't have great data for other 64-bit CPUs, but for long strings we know that Spooky is slightly faster than CityHash on some relatively recent AMD x86-64 CPUs, for example. Note that CityHashCrc128 is declared in citycrc.h.