Function BenchmarkBytes

cmp/compare_test.go:2962–3008

BenchmarkBytes benchmarks the performance of performing Equal or Diff on large slices of bytes.

(b *testing.B)

// BenchmarkBytes benchmarks the performance of performing Equal or Diff on
// large slices of bytes.
func BenchmarkBytes(b *testing.B) {
	// Create a list of PathFilters that never apply, but are evaluated.
	const maxFilters = 5
	var filters cmp.Options
	errorIface := reflect.TypeOf((*error)(nil)).Elem()
	for i := 0; i <= maxFilters; i++ {
		filters = append(filters, cmp.FilterPath(func(p cmp.Path) bool {
			return p.Last().Type().AssignableTo(errorIface) // Never true
		}, cmp.Ignore()))
	}

	type benchSize struct {
		label string
		size  int64
	}
	for _, ts := range []benchSize{
		{"4KiB", 1 << 12},
		{"64KiB", 1 << 16},
		{"1MiB", 1 << 20},
		{"16MiB", 1 << 24},
	} {
		bx := append(append(make([]byte, ts.size/2), 'x'), make([]byte, ts.size/2)...)
		by := append(append(make([]byte, ts.size/2), 'y'), make([]byte, ts.size/2)...)
		b.Run(ts.label, func(b *testing.B) {
			// Iteratively add more filters that never apply, but are evaluated
			// to measure the cost of simply evaluating each filter.
			for i := 0; i <= maxFilters; i++ {
				b.Run(fmt.Sprintf("EqualFilter%d", i), func(b *testing.B) {
					b.ReportAllocs()
					b.SetBytes(2 * ts.size)
					for j := 0; j < b.N; j++ {
						cmp.Equal(bx, by, filters[:i]...)
					}
				})
			}
			for i := 0; i <= maxFilters; i++ {
				b.Run(fmt.Sprintf("DiffFilter%d", i), func(b *testing.B) {
					b.ReportAllocs()
					b.SetBytes(2 * ts.size)
					for j := 0; j < b.N; j++ {
						cmp.Diff(bx, by, filters[:i]...)
					}
				})
			}
		})
	}
}