$ go test -bench=.
BenchmarkCountBitsInt8PopCnt-4      	300000000	         4.30 ns/op
BenchmarkCountBitsInt16PopCnt-4     	300000000	         3.83 ns/op
BenchmarkCountBitsInt32PopCnt-4     	300000000	         3.64 ns/op
BenchmarkCountBitsInt64PopCnt-4     	500000000	         3.60 ns/op
BenchmarkCountBitsIntPopCnt-4       	300000000	         5.72 ns/op
BenchmarkCountBitsUint8PopCnt-4     	1000000000	         2.98 ns/op
BenchmarkCountBitsUint16PopCnt-4    	500000000	         3.23 ns/op
BenchmarkCountBitsUint32PopCnt-4    	500000000	         3.00 ns/op
BenchmarkCountBitsUint64PopCnt-4    	1000000000	         2.94 ns/op
BenchmarkCountBitsUintPopCnt-4      	300000000	         5.04 ns/op
BenchmarkCountBitsBytePopCnt-4      	300000000	         3.99 ns/op
BenchmarkCountBitsRunePopCnt-4      	300000000	         3.83 ns/op
BenchmarkCountBitsInt8-4            	2000000000	         0.74 ns/op
BenchmarkCountBitsInt16-4           	2000000000	         1.54 ns/op
BenchmarkCountBitsInt32-4           	1000000000	         2.63 ns/op
BenchmarkCountBitsInt64-4           	1000000000	         2.56 ns/op
BenchmarkCountBitsInt-4             	200000000	         7.23 ns/op
BenchmarkCountBitsUint16-4          	2000000000	         1.51 ns/op
BenchmarkCountBitsUint32-4          	500000000	         4.00 ns/op
BenchmarkCountBitsUint64-4          	1000000000	         2.64 ns/op
BenchmarkCountBitsUint64Alt-4       	200000000	         7.60 ns/op
BenchmarkCountBitsUint-4            	300000000	         5.48 ns/op
BenchmarkCountBitsUintReference-4   	100000000	        19.2 ns/op
BenchmarkCountBitsByte-4            	2000000000	         0.75 ns/op
BenchmarkCountBitsByteAlt-4         	1000000000	         2.37 ns/op
BenchmarkCountBitsRune-4            	500000000	         2.85 ns/op
PASS
ok  	_/Users/bmf/Projects/hamming	58.305s
$

go get -u github.com/steakknife/hamming  # master is always stable