Performance deep dive

In this approach, we'll find out how to most efficiently determine the Scrabble Score in Go.

The approaches page lists two idiomatic approaches to this exercise:

1. Using map.
2. Using a switch on runes.

For our performance investigation, we'll also include a third approach that uses a switch on strings.

Benchmarks

To benchmark the approaches, we ran the following Benchmark code for each approach:

func BenchmarkScore(b *testing.B) {
	if testing.Short() {
		b.Skip("skipping benchmark in short mode.")
	}
	for i := 0; i < b.N; i++ {
		for _, test := range scrabbleScoreTests {
			Score(test.input)
		}
	}
}

and received the following results:

map
BenchmarkScore-12    	 1544814	       711.7 ns/op	       0 B/op	       0 allocs/op

switch on runes
BenchmarkScore-12    	 4171696	       242.1 ns/op	       0 B/op	       0 allocs/op

switch on strings
BenchmarkScore-12    	  413484	      2527 ns/op	    1088 B/op	      12 allocs/op

Generally, the fewer bytes allocated per op (B/op) the faster (i.e. the fewer ns/op) the implementation. More info on reading benchmarks can be found here.

Using switch on runes was about three times faster than the next fastest approach, which was using a map. Using a switch on each letter being a separate string was over ten times slower than switching on runes.