From 6bd56fcaebde61eb6bd21906a7d7136d009be4a6 Mon Sep 17 00:00:00 2001 From: Austin Clements Date: Thu, 12 Dec 2024 18:19:43 -0500 Subject: testing: improve b.Loop example The current b.Loop example doesn't focus on the basic usage of b.Loop. Replace this with a new example that uses (slightly) more realistic things to demonstrate the most salient points of b.Loop. We also move the example into an example file so that we can write a real Benchmark function and a real function to be benchmarks, which makes this much closer to what a user would actually write. Updates #61515. Change-Id: I4d830b3bfe3eb3cd8cdecef469fea0541baebb43 Reviewed-on: https://go-review.googlesource.com/c/go/+/635896 Auto-Submit: Austin Clements Reviewed-by: Junyang Shao Reviewed-by: Cherry Mui LUCI-TryBot-Result: Go LUCI --- src/testing/example_loop_test.go | 48 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 48 insertions(+) create mode 100644 src/testing/example_loop_test.go (limited to 'src/testing/example_loop_test.go') diff --git a/src/testing/example_loop_test.go b/src/testing/example_loop_test.go new file mode 100644 index 0000000000..eff8bab352 --- /dev/null +++ b/src/testing/example_loop_test.go @@ -0,0 +1,48 @@ +// Copyright 2024 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package testing_test + +import ( + "math/rand/v2" + "testing" +) + +// ExBenchmark shows how to use b.Loop in a benchmark. +// +// (If this were a real benchmark, not an example, this would be named +// BenchmarkSomething.) +func ExBenchmark(b *testing.B) { + // Generate a large random slice to use as an input. + // Since this is done before the first call to b.Loop(), + // it doesn't count toward the benchmark time. + input := make([]int, 128<<10) + for i := range input { + input[i] = rand.Int() + } + + // Perform the benchmark. + for b.Loop() { + // Normally, the compiler would be allowed to optimize away the call + // to sum because it has no side effects and the result isn't used. + // However, inside a b.Loop loop, the compiler ensures function calls + // aren't optimized away. + sum(input) + } + + // Outside the loop, the timer is stopped, so we could perform + // cleanup if necessary without affecting the result. +} + +func sum(data []int) int { + total := 0 + for _, value := range data { + total += value + } + return total +} + +func ExampleB_Loop() { + testing.Benchmark(ExBenchmark) +} -- cgit v1.3