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-rw-r--r--src/testing/benchmark.go840
1 files changed, 840 insertions, 0 deletions
diff --git a/src/testing/benchmark.go b/src/testing/benchmark.go
new file mode 100644
index 0000000..9491213
--- /dev/null
+++ b/src/testing/benchmark.go
@@ -0,0 +1,840 @@
+// Copyright 2009 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
+
+import (
+ "flag"
+ "fmt"
+ "internal/sysinfo"
+ "io"
+ "math"
+ "os"
+ "runtime"
+ "sort"
+ "strconv"
+ "strings"
+ "sync"
+ "sync/atomic"
+ "time"
+ "unicode"
+)
+
+func initBenchmarkFlags() {
+ matchBenchmarks = flag.String("test.bench", "", "run only benchmarks matching `regexp`")
+ benchmarkMemory = flag.Bool("test.benchmem", false, "print memory allocations for benchmarks")
+ flag.Var(&benchTime, "test.benchtime", "run each benchmark for duration `d` or N times if `d` is of the form Nx")
+}
+
+var (
+ matchBenchmarks *string
+ benchmarkMemory *bool
+
+ benchTime = durationOrCountFlag{d: 1 * time.Second} // changed during test of testing package
+)
+
+type durationOrCountFlag struct {
+ d time.Duration
+ n int
+ allowZero bool
+}
+
+func (f *durationOrCountFlag) String() string {
+ if f.n > 0 {
+ return fmt.Sprintf("%dx", f.n)
+ }
+ return f.d.String()
+}
+
+func (f *durationOrCountFlag) Set(s string) error {
+ if strings.HasSuffix(s, "x") {
+ n, err := strconv.ParseInt(s[:len(s)-1], 10, 0)
+ if err != nil || n < 0 || (!f.allowZero && n == 0) {
+ return fmt.Errorf("invalid count")
+ }
+ *f = durationOrCountFlag{n: int(n)}
+ return nil
+ }
+ d, err := time.ParseDuration(s)
+ if err != nil || d < 0 || (!f.allowZero && d == 0) {
+ return fmt.Errorf("invalid duration")
+ }
+ *f = durationOrCountFlag{d: d}
+ return nil
+}
+
+// Global lock to ensure only one benchmark runs at a time.
+var benchmarkLock sync.Mutex
+
+// Used for every benchmark for measuring memory.
+var memStats runtime.MemStats
+
+// InternalBenchmark is an internal type but exported because it is cross-package;
+// it is part of the implementation of the "go test" command.
+type InternalBenchmark struct {
+ Name string
+ F func(b *B)
+}
+
+// B is a type passed to [Benchmark] functions to manage benchmark
+// timing and to specify the number of iterations to run.
+//
+// A benchmark ends when its Benchmark function returns or calls any of the methods
+// FailNow, Fatal, Fatalf, SkipNow, Skip, or Skipf. Those methods must be called
+// only from the goroutine running the Benchmark function.
+// The other reporting methods, such as the variations of Log and Error,
+// may be called simultaneously from multiple goroutines.
+//
+// Like in tests, benchmark logs are accumulated during execution
+// and dumped to standard output when done. Unlike in tests, benchmark logs
+// are always printed, so as not to hide output whose existence may be
+// affecting benchmark results.
+type B struct {
+ common
+ importPath string // import path of the package containing the benchmark
+ context *benchContext
+ N int
+ previousN int // number of iterations in the previous run
+ previousDuration time.Duration // total duration of the previous run
+ benchFunc func(b *B)
+ benchTime durationOrCountFlag
+ bytes int64
+ missingBytes bool // one of the subbenchmarks does not have bytes set.
+ timerOn bool
+ showAllocResult bool
+ result BenchmarkResult
+ parallelism int // RunParallel creates parallelism*GOMAXPROCS goroutines
+ // The initial states of memStats.Mallocs and memStats.TotalAlloc.
+ startAllocs uint64
+ startBytes uint64
+ // The net total of this test after being run.
+ netAllocs uint64
+ netBytes uint64
+ // Extra metrics collected by ReportMetric.
+ extra map[string]float64
+}
+
+// StartTimer starts timing a test. This function is called automatically
+// before a benchmark starts, but it can also be used to resume timing after
+// a call to [B.StopTimer].
+func (b *B) StartTimer() {
+ if !b.timerOn {
+ runtime.ReadMemStats(&memStats)
+ b.startAllocs = memStats.Mallocs
+ b.startBytes = memStats.TotalAlloc
+ b.start = time.Now()
+ b.timerOn = true
+ }
+}
+
+// StopTimer stops timing a test. This can be used to pause the timer
+// while performing complex initialization that you don't
+// want to measure.
+func (b *B) StopTimer() {
+ if b.timerOn {
+ b.duration += time.Since(b.start)
+ runtime.ReadMemStats(&memStats)
+ b.netAllocs += memStats.Mallocs - b.startAllocs
+ b.netBytes += memStats.TotalAlloc - b.startBytes
+ b.timerOn = false
+ }
+}
+
+// ResetTimer zeroes the elapsed benchmark time and memory allocation counters
+// and deletes user-reported metrics.
+// It does not affect whether the timer is running.
+func (b *B) ResetTimer() {
+ if b.extra == nil {
+ // Allocate the extra map before reading memory stats.
+ // Pre-size it to make more allocation unlikely.
+ b.extra = make(map[string]float64, 16)
+ } else {
+ clear(b.extra)
+ }
+ if b.timerOn {
+ runtime.ReadMemStats(&memStats)
+ b.startAllocs = memStats.Mallocs
+ b.startBytes = memStats.TotalAlloc
+ b.start = time.Now()
+ }
+ b.duration = 0
+ b.netAllocs = 0
+ b.netBytes = 0
+}
+
+// SetBytes records the number of bytes processed in a single operation.
+// If this is called, the benchmark will report ns/op and MB/s.
+func (b *B) SetBytes(n int64) { b.bytes = n }
+
+// ReportAllocs enables malloc statistics for this benchmark.
+// It is equivalent to setting -test.benchmem, but it only affects the
+// benchmark function that calls ReportAllocs.
+func (b *B) ReportAllocs() {
+ b.showAllocResult = true
+}
+
+// runN runs a single benchmark for the specified number of iterations.
+func (b *B) runN(n int) {
+ benchmarkLock.Lock()
+ defer benchmarkLock.Unlock()
+ defer func() {
+ b.runCleanup(normalPanic)
+ b.checkRaces()
+ }()
+ // Try to get a comparable environment for each run
+ // by clearing garbage from previous runs.
+ runtime.GC()
+ b.resetRaces()
+ b.N = n
+ b.parallelism = 1
+ b.ResetTimer()
+ b.StartTimer()
+ b.benchFunc(b)
+ b.StopTimer()
+ b.previousN = n
+ b.previousDuration = b.duration
+}
+
+// run1 runs the first iteration of benchFunc. It reports whether more
+// iterations of this benchmarks should be run.
+func (b *B) run1() bool {
+ if ctx := b.context; ctx != nil {
+ // Extend maxLen, if needed.
+ if n := len(b.name) + ctx.extLen + 1; n > ctx.maxLen {
+ ctx.maxLen = n + 8 // Add additional slack to avoid too many jumps in size.
+ }
+ }
+ go func() {
+ // Signal that we're done whether we return normally
+ // or by FailNow's runtime.Goexit.
+ defer func() {
+ b.signal <- true
+ }()
+
+ b.runN(1)
+ }()
+ <-b.signal
+ if b.failed {
+ fmt.Fprintf(b.w, "%s--- FAIL: %s\n%s", b.chatty.prefix(), b.name, b.output)
+ return false
+ }
+ // Only print the output if we know we are not going to proceed.
+ // Otherwise it is printed in processBench.
+ b.mu.RLock()
+ finished := b.finished
+ b.mu.RUnlock()
+ if b.hasSub.Load() || finished {
+ tag := "BENCH"
+ if b.skipped {
+ tag = "SKIP"
+ }
+ if b.chatty != nil && (len(b.output) > 0 || finished) {
+ b.trimOutput()
+ fmt.Fprintf(b.w, "%s--- %s: %s\n%s", b.chatty.prefix(), tag, b.name, b.output)
+ }
+ return false
+ }
+ return true
+}
+
+var labelsOnce sync.Once
+
+// run executes the benchmark in a separate goroutine, including all of its
+// subbenchmarks. b must not have subbenchmarks.
+func (b *B) run() {
+ labelsOnce.Do(func() {
+ fmt.Fprintf(b.w, "goos: %s\n", runtime.GOOS)
+ fmt.Fprintf(b.w, "goarch: %s\n", runtime.GOARCH)
+ if b.importPath != "" {
+ fmt.Fprintf(b.w, "pkg: %s\n", b.importPath)
+ }
+ if cpu := sysinfo.CPUName(); cpu != "" {
+ fmt.Fprintf(b.w, "cpu: %s\n", cpu)
+ }
+ })
+ if b.context != nil {
+ // Running go test --test.bench
+ b.context.processBench(b) // Must call doBench.
+ } else {
+ // Running func Benchmark.
+ b.doBench()
+ }
+}
+
+func (b *B) doBench() BenchmarkResult {
+ go b.launch()
+ <-b.signal
+ return b.result
+}
+
+// launch launches the benchmark function. It gradually increases the number
+// of benchmark iterations until the benchmark runs for the requested benchtime.
+// launch is run by the doBench function as a separate goroutine.
+// run1 must have been called on b.
+func (b *B) launch() {
+ // Signal that we're done whether we return normally
+ // or by FailNow's runtime.Goexit.
+ defer func() {
+ b.signal <- true
+ }()
+
+ // Run the benchmark for at least the specified amount of time.
+ if b.benchTime.n > 0 {
+ // We already ran a single iteration in run1.
+ // If -benchtime=1x was requested, use that result.
+ // See https://golang.org/issue/32051.
+ if b.benchTime.n > 1 {
+ b.runN(b.benchTime.n)
+ }
+ } else {
+ d := b.benchTime.d
+ for n := int64(1); !b.failed && b.duration < d && n < 1e9; {
+ last := n
+ // Predict required iterations.
+ goalns := d.Nanoseconds()
+ prevIters := int64(b.N)
+ prevns := b.duration.Nanoseconds()
+ if prevns <= 0 {
+ // Round up, to avoid div by zero.
+ prevns = 1
+ }
+ // Order of operations matters.
+ // For very fast benchmarks, prevIters ~= prevns.
+ // If you divide first, you get 0 or 1,
+ // which can hide an order of magnitude in execution time.
+ // So multiply first, then divide.
+ n = goalns * prevIters / prevns
+ // Run more iterations than we think we'll need (1.2x).
+ n += n / 5
+ // Don't grow too fast in case we had timing errors previously.
+ n = min(n, 100*last)
+ // Be sure to run at least one more than last time.
+ n = max(n, last+1)
+ // Don't run more than 1e9 times. (This also keeps n in int range on 32 bit platforms.)
+ n = min(n, 1e9)
+ b.runN(int(n))
+ }
+ }
+ b.result = BenchmarkResult{b.N, b.duration, b.bytes, b.netAllocs, b.netBytes, b.extra}
+}
+
+// Elapsed returns the measured elapsed time of the benchmark.
+// The duration reported by Elapsed matches the one measured by
+// [B.StartTimer], [B.StopTimer], and [B.ResetTimer].
+func (b *B) Elapsed() time.Duration {
+ d := b.duration
+ if b.timerOn {
+ d += time.Since(b.start)
+ }
+ return d
+}
+
+// ReportMetric adds "n unit" to the reported benchmark results.
+// If the metric is per-iteration, the caller should divide by b.N,
+// and by convention units should end in "/op".
+// ReportMetric overrides any previously reported value for the same unit.
+// ReportMetric panics if unit is the empty string or if unit contains
+// any whitespace.
+// If unit is a unit normally reported by the benchmark framework itself
+// (such as "allocs/op"), ReportMetric will override that metric.
+// Setting "ns/op" to 0 will suppress that built-in metric.
+func (b *B) ReportMetric(n float64, unit string) {
+ if unit == "" {
+ panic("metric unit must not be empty")
+ }
+ if strings.IndexFunc(unit, unicode.IsSpace) >= 0 {
+ panic("metric unit must not contain whitespace")
+ }
+ b.extra[unit] = n
+}
+
+// BenchmarkResult contains the results of a benchmark run.
+type BenchmarkResult struct {
+ N int // The number of iterations.
+ T time.Duration // The total time taken.
+ Bytes int64 // Bytes processed in one iteration.
+ MemAllocs uint64 // The total number of memory allocations.
+ MemBytes uint64 // The total number of bytes allocated.
+
+ // Extra records additional metrics reported by ReportMetric.
+ Extra map[string]float64
+}
+
+// NsPerOp returns the "ns/op" metric.
+func (r BenchmarkResult) NsPerOp() int64 {
+ if v, ok := r.Extra["ns/op"]; ok {
+ return int64(v)
+ }
+ if r.N <= 0 {
+ return 0
+ }
+ return r.T.Nanoseconds() / int64(r.N)
+}
+
+// mbPerSec returns the "MB/s" metric.
+func (r BenchmarkResult) mbPerSec() float64 {
+ if v, ok := r.Extra["MB/s"]; ok {
+ return v
+ }
+ if r.Bytes <= 0 || r.T <= 0 || r.N <= 0 {
+ return 0
+ }
+ return (float64(r.Bytes) * float64(r.N) / 1e6) / r.T.Seconds()
+}
+
+// AllocsPerOp returns the "allocs/op" metric,
+// which is calculated as r.MemAllocs / r.N.
+func (r BenchmarkResult) AllocsPerOp() int64 {
+ if v, ok := r.Extra["allocs/op"]; ok {
+ return int64(v)
+ }
+ if r.N <= 0 {
+ return 0
+ }
+ return int64(r.MemAllocs) / int64(r.N)
+}
+
+// AllocedBytesPerOp returns the "B/op" metric,
+// which is calculated as r.MemBytes / r.N.
+func (r BenchmarkResult) AllocedBytesPerOp() int64 {
+ if v, ok := r.Extra["B/op"]; ok {
+ return int64(v)
+ }
+ if r.N <= 0 {
+ return 0
+ }
+ return int64(r.MemBytes) / int64(r.N)
+}
+
+// String returns a summary of the benchmark results.
+// It follows the benchmark result line format from
+// https://golang.org/design/14313-benchmark-format, not including the
+// benchmark name.
+// Extra metrics override built-in metrics of the same name.
+// String does not include allocs/op or B/op, since those are reported
+// by [BenchmarkResult.MemString].
+func (r BenchmarkResult) String() string {
+ buf := new(strings.Builder)
+ fmt.Fprintf(buf, "%8d", r.N)
+
+ // Get ns/op as a float.
+ ns, ok := r.Extra["ns/op"]
+ if !ok {
+ ns = float64(r.T.Nanoseconds()) / float64(r.N)
+ }
+ if ns != 0 {
+ buf.WriteByte('\t')
+ prettyPrint(buf, ns, "ns/op")
+ }
+
+ if mbs := r.mbPerSec(); mbs != 0 {
+ fmt.Fprintf(buf, "\t%7.2f MB/s", mbs)
+ }
+
+ // Print extra metrics that aren't represented in the standard
+ // metrics.
+ var extraKeys []string
+ for k := range r.Extra {
+ switch k {
+ case "ns/op", "MB/s", "B/op", "allocs/op":
+ // Built-in metrics reported elsewhere.
+ continue
+ }
+ extraKeys = append(extraKeys, k)
+ }
+ sort.Strings(extraKeys)
+ for _, k := range extraKeys {
+ buf.WriteByte('\t')
+ prettyPrint(buf, r.Extra[k], k)
+ }
+ return buf.String()
+}
+
+func prettyPrint(w io.Writer, x float64, unit string) {
+ // Print all numbers with 10 places before the decimal point
+ // and small numbers with four sig figs. Field widths are
+ // chosen to fit the whole part in 10 places while aligning
+ // the decimal point of all fractional formats.
+ var format string
+ switch y := math.Abs(x); {
+ case y == 0 || y >= 999.95:
+ format = "%10.0f %s"
+ case y >= 99.995:
+ format = "%12.1f %s"
+ case y >= 9.9995:
+ format = "%13.2f %s"
+ case y >= 0.99995:
+ format = "%14.3f %s"
+ case y >= 0.099995:
+ format = "%15.4f %s"
+ case y >= 0.0099995:
+ format = "%16.5f %s"
+ case y >= 0.00099995:
+ format = "%17.6f %s"
+ default:
+ format = "%18.7f %s"
+ }
+ fmt.Fprintf(w, format, x, unit)
+}
+
+// MemString returns r.AllocedBytesPerOp and r.AllocsPerOp in the same format as 'go test'.
+func (r BenchmarkResult) MemString() string {
+ return fmt.Sprintf("%8d B/op\t%8d allocs/op",
+ r.AllocedBytesPerOp(), r.AllocsPerOp())
+}
+
+// benchmarkName returns full name of benchmark including procs suffix.
+func benchmarkName(name string, n int) string {
+ if n != 1 {
+ return fmt.Sprintf("%s-%d", name, n)
+ }
+ return name
+}
+
+type benchContext struct {
+ match *matcher
+
+ maxLen int // The largest recorded benchmark name.
+ extLen int // Maximum extension length.
+}
+
+// RunBenchmarks is an internal function but exported because it is cross-package;
+// it is part of the implementation of the "go test" command.
+func RunBenchmarks(matchString func(pat, str string) (bool, error), benchmarks []InternalBenchmark) {
+ runBenchmarks("", matchString, benchmarks)
+}
+
+func runBenchmarks(importPath string, matchString func(pat, str string) (bool, error), benchmarks []InternalBenchmark) bool {
+ // If no flag was specified, don't run benchmarks.
+ if len(*matchBenchmarks) == 0 {
+ return true
+ }
+ // Collect matching benchmarks and determine longest name.
+ maxprocs := 1
+ for _, procs := range cpuList {
+ if procs > maxprocs {
+ maxprocs = procs
+ }
+ }
+ ctx := &benchContext{
+ match: newMatcher(matchString, *matchBenchmarks, "-test.bench", *skip),
+ extLen: len(benchmarkName("", maxprocs)),
+ }
+ var bs []InternalBenchmark
+ for _, Benchmark := range benchmarks {
+ if _, matched, _ := ctx.match.fullName(nil, Benchmark.Name); matched {
+ bs = append(bs, Benchmark)
+ benchName := benchmarkName(Benchmark.Name, maxprocs)
+ if l := len(benchName) + ctx.extLen + 1; l > ctx.maxLen {
+ ctx.maxLen = l
+ }
+ }
+ }
+ main := &B{
+ common: common{
+ name: "Main",
+ w: os.Stdout,
+ bench: true,
+ },
+ importPath: importPath,
+ benchFunc: func(b *B) {
+ for _, Benchmark := range bs {
+ b.Run(Benchmark.Name, Benchmark.F)
+ }
+ },
+ benchTime: benchTime,
+ context: ctx,
+ }
+ if Verbose() {
+ main.chatty = newChattyPrinter(main.w)
+ }
+ main.runN(1)
+ return !main.failed
+}
+
+// processBench runs bench b for the configured CPU counts and prints the results.
+func (ctx *benchContext) processBench(b *B) {
+ for i, procs := range cpuList {
+ for j := uint(0); j < *count; j++ {
+ runtime.GOMAXPROCS(procs)
+ benchName := benchmarkName(b.name, procs)
+
+ // If it's chatty, we've already printed this information.
+ if b.chatty == nil {
+ fmt.Fprintf(b.w, "%-*s\t", ctx.maxLen, benchName)
+ }
+ // Recompute the running time for all but the first iteration.
+ if i > 0 || j > 0 {
+ b = &B{
+ common: common{
+ signal: make(chan bool),
+ name: b.name,
+ w: b.w,
+ chatty: b.chatty,
+ bench: true,
+ },
+ benchFunc: b.benchFunc,
+ benchTime: b.benchTime,
+ }
+ b.run1()
+ }
+ r := b.doBench()
+ if b.failed {
+ // The output could be very long here, but probably isn't.
+ // We print it all, regardless, because we don't want to trim the reason
+ // the benchmark failed.
+ fmt.Fprintf(b.w, "%s--- FAIL: %s\n%s", b.chatty.prefix(), benchName, b.output)
+ continue
+ }
+ results := r.String()
+ if b.chatty != nil {
+ fmt.Fprintf(b.w, "%-*s\t", ctx.maxLen, benchName)
+ }
+ if *benchmarkMemory || b.showAllocResult {
+ results += "\t" + r.MemString()
+ }
+ fmt.Fprintln(b.w, results)
+ // Unlike with tests, we ignore the -chatty flag and always print output for
+ // benchmarks since the output generation time will skew the results.
+ if len(b.output) > 0 {
+ b.trimOutput()
+ fmt.Fprintf(b.w, "%s--- BENCH: %s\n%s", b.chatty.prefix(), benchName, b.output)
+ }
+ if p := runtime.GOMAXPROCS(-1); p != procs {
+ fmt.Fprintf(os.Stderr, "testing: %s left GOMAXPROCS set to %d\n", benchName, p)
+ }
+ if b.chatty != nil && b.chatty.json {
+ b.chatty.Updatef("", "=== NAME %s\n", "")
+ }
+ }
+ }
+}
+
+// If hideStdoutForTesting is true, Run does not print the benchName.
+// This avoids a spurious print during 'go test' on package testing itself,
+// which invokes b.Run in its own tests (see sub_test.go).
+var hideStdoutForTesting = false
+
+// Run benchmarks f as a subbenchmark with the given name. It reports
+// whether there were any failures.
+//
+// A subbenchmark is like any other benchmark. A benchmark that calls Run at
+// least once will not be measured itself and will be called once with N=1.
+func (b *B) Run(name string, f func(b *B)) bool {
+ // Since b has subbenchmarks, we will no longer run it as a benchmark itself.
+ // Release the lock and acquire it on exit to ensure locks stay paired.
+ b.hasSub.Store(true)
+ benchmarkLock.Unlock()
+ defer benchmarkLock.Lock()
+
+ benchName, ok, partial := b.name, true, false
+ if b.context != nil {
+ benchName, ok, partial = b.context.match.fullName(&b.common, name)
+ }
+ if !ok {
+ return true
+ }
+ var pc [maxStackLen]uintptr
+ n := runtime.Callers(2, pc[:])
+ sub := &B{
+ common: common{
+ signal: make(chan bool),
+ name: benchName,
+ parent: &b.common,
+ level: b.level + 1,
+ creator: pc[:n],
+ w: b.w,
+ chatty: b.chatty,
+ bench: true,
+ },
+ importPath: b.importPath,
+ benchFunc: f,
+ benchTime: b.benchTime,
+ context: b.context,
+ }
+ if partial {
+ // Partial name match, like -bench=X/Y matching BenchmarkX.
+ // Only process sub-benchmarks, if any.
+ sub.hasSub.Store(true)
+ }
+
+ if b.chatty != nil {
+ labelsOnce.Do(func() {
+ fmt.Printf("goos: %s\n", runtime.GOOS)
+ fmt.Printf("goarch: %s\n", runtime.GOARCH)
+ if b.importPath != "" {
+ fmt.Printf("pkg: %s\n", b.importPath)
+ }
+ if cpu := sysinfo.CPUName(); cpu != "" {
+ fmt.Printf("cpu: %s\n", cpu)
+ }
+ })
+
+ if !hideStdoutForTesting {
+ if b.chatty.json {
+ b.chatty.Updatef(benchName, "=== RUN %s\n", benchName)
+ }
+ fmt.Println(benchName)
+ }
+ }
+
+ if sub.run1() {
+ sub.run()
+ }
+ b.add(sub.result)
+ return !sub.failed
+}
+
+// add simulates running benchmarks in sequence in a single iteration. It is
+// used to give some meaningful results in case func Benchmark is used in
+// combination with Run.
+func (b *B) add(other BenchmarkResult) {
+ r := &b.result
+ // The aggregated BenchmarkResults resemble running all subbenchmarks as
+ // in sequence in a single benchmark.
+ r.N = 1
+ r.T += time.Duration(other.NsPerOp())
+ if other.Bytes == 0 {
+ // Summing Bytes is meaningless in aggregate if not all subbenchmarks
+ // set it.
+ b.missingBytes = true
+ r.Bytes = 0
+ }
+ if !b.missingBytes {
+ r.Bytes += other.Bytes
+ }
+ r.MemAllocs += uint64(other.AllocsPerOp())
+ r.MemBytes += uint64(other.AllocedBytesPerOp())
+}
+
+// trimOutput shortens the output from a benchmark, which can be very long.
+func (b *B) trimOutput() {
+ // The output is likely to appear multiple times because the benchmark
+ // is run multiple times, but at least it will be seen. This is not a big deal
+ // because benchmarks rarely print, but just in case, we trim it if it's too long.
+ const maxNewlines = 10
+ for nlCount, j := 0, 0; j < len(b.output); j++ {
+ if b.output[j] == '\n' {
+ nlCount++
+ if nlCount >= maxNewlines {
+ b.output = append(b.output[:j], "\n\t... [output truncated]\n"...)
+ break
+ }
+ }
+ }
+}
+
+// A PB is used by RunParallel for running parallel benchmarks.
+type PB struct {
+ globalN *atomic.Uint64 // shared between all worker goroutines iteration counter
+ grain uint64 // acquire that many iterations from globalN at once
+ cache uint64 // local cache of acquired iterations
+ bN uint64 // total number of iterations to execute (b.N)
+}
+
+// Next reports whether there are more iterations to execute.
+func (pb *PB) Next() bool {
+ if pb.cache == 0 {
+ n := pb.globalN.Add(pb.grain)
+ if n <= pb.bN {
+ pb.cache = pb.grain
+ } else if n < pb.bN+pb.grain {
+ pb.cache = pb.bN + pb.grain - n
+ } else {
+ return false
+ }
+ }
+ pb.cache--
+ return true
+}
+
+// RunParallel runs a benchmark in parallel.
+// It creates multiple goroutines and distributes b.N iterations among them.
+// The number of goroutines defaults to GOMAXPROCS. To increase parallelism for
+// non-CPU-bound benchmarks, call [B.SetParallelism] before RunParallel.
+// RunParallel is usually used with the go test -cpu flag.
+//
+// The body function will be run in each goroutine. It should set up any
+// goroutine-local state and then iterate until pb.Next returns false.
+// It should not use the [B.StartTimer], [B.StopTimer], or [B.ResetTimer] functions,
+// because they have global effect. It should also not call [B.Run].
+//
+// RunParallel reports ns/op values as wall time for the benchmark as a whole,
+// not the sum of wall time or CPU time over each parallel goroutine.
+func (b *B) RunParallel(body func(*PB)) {
+ if b.N == 0 {
+ return // Nothing to do when probing.
+ }
+ // Calculate grain size as number of iterations that take ~100µs.
+ // 100µs is enough to amortize the overhead and provide sufficient
+ // dynamic load balancing.
+ grain := uint64(0)
+ if b.previousN > 0 && b.previousDuration > 0 {
+ grain = 1e5 * uint64(b.previousN) / uint64(b.previousDuration)
+ }
+ if grain < 1 {
+ grain = 1
+ }
+ // We expect the inner loop and function call to take at least 10ns,
+ // so do not do more than 100µs/10ns=1e4 iterations.
+ if grain > 1e4 {
+ grain = 1e4
+ }
+
+ var n atomic.Uint64
+ numProcs := b.parallelism * runtime.GOMAXPROCS(0)
+ var wg sync.WaitGroup
+ wg.Add(numProcs)
+ for p := 0; p < numProcs; p++ {
+ go func() {
+ defer wg.Done()
+ pb := &PB{
+ globalN: &n,
+ grain: grain,
+ bN: uint64(b.N),
+ }
+ body(pb)
+ }()
+ }
+ wg.Wait()
+ if n.Load() <= uint64(b.N) && !b.Failed() {
+ b.Fatal("RunParallel: body exited without pb.Next() == false")
+ }
+}
+
+// SetParallelism sets the number of goroutines used by [B.RunParallel] to p*GOMAXPROCS.
+// There is usually no need to call SetParallelism for CPU-bound benchmarks.
+// If p is less than 1, this call will have no effect.
+func (b *B) SetParallelism(p int) {
+ if p >= 1 {
+ b.parallelism = p
+ }
+}
+
+// Benchmark benchmarks a single function. It is useful for creating
+// custom benchmarks that do not use the "go test" command.
+//
+// If f depends on testing flags, then [Init] must be used to register
+// those flags before calling Benchmark and before calling [flag.Parse].
+//
+// If f calls Run, the result will be an estimate of running all its
+// subbenchmarks that don't call Run in sequence in a single benchmark.
+func Benchmark(f func(b *B)) BenchmarkResult {
+ b := &B{
+ common: common{
+ signal: make(chan bool),
+ w: discard{},
+ },
+ benchFunc: f,
+ benchTime: benchTime,
+ }
+ if b.run1() {
+ b.run()
+ }
+ return b.result
+}
+
+type discard struct{}
+
+func (discard) Write(b []byte) (n int, err error) { return len(b), nil }
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-03 16:43:36 +0000