Beautiful Code — go sort
sort: optimize average calculation in symMerge and doPivot.
Change code of the form `i + (j-i)/2` to `int(uint(i+j) >> 1)`.
The optimized average calculation uses fewer instructions to calculate the average without overflowing at the addition.
Analogous to https://golang.org/cl/36332.
name old time/op new time/op delta StableString1K-4 49.6µs ± 3% 49.1µs ± 8% ~ (p=0.659 n=16+19) StableInt1K-4 160µs ±10% 148µs ± 5% -7.29% (p=0.000 n=20+16) StableInt1K_Slice-4 139µs ± 4% 136µs ± 3% -2.52% (p=0.000 n=20+16) StableInt64K-4 8.84ms ± 6% 8.57ms ± 5% -3.07% (p=0.001 n=20+19) Stable1e2-4 162µs ±19% 147µs ±16% -8.79% (p=0.002 n=20+20) Stable1e4-4 31.0ms ± 5% 30.6ms ± 5% ~ (p=0.221 n=20+20) Stable1e6-4 6.37s ± 3% 6.27s ± 2% -1.67% (p=0.000 n=19+20)
更多细节可以参考：
https://github.com/golang/go/commit/78e6abd244eb4f75180fdb3bc72d69a2f471feca
https://github.com/golang/go/blob/master/src/sort/sort.go