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testing: increase benchmark output to four significant figures

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Currently, the benchmark output from the testing package prints small
values with three significant figures. This means it can only
distinguish 1 part in 100, or a 1% error, which can be enough to throw
off further analysis of the output. This CL increases it to four
significant figures. For time values, at least, anything beyond four
significant figures is almost certainly noise.

Fixes #34626.

Change-Id: I3bcf305427130026276e6a4c78167989319f280c
Reviewed-on: https://go-review.googlesource.com/c/go/+/267102
Trust: Austin Clements <austin@google.com>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Michael Pratt <mpratt@google.com>
This commit is contained in:
Austin Clements 2020-11-02 08:48:23 -05:00
parent 5e371e0f93
commit afe7c8d0b2
2 changed files with 23 additions and 18 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

20
src/testing/benchmark.go
View file

@ -451,23 +451,27 @@ func (r BenchmarkResult) String() string {
func prettyPrint(w io.Writer, x float64, unit string) {
// Print all numbers with 10 places before the decimal point
// and small numbers with three sig figs.
// 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 >= 99.95:
case y == 0 || y >= 999.95:
format = "%10.0f %s"
case y >= 9.995:
case y >= 99.995:
format = "%12.1f %s"
case y >= 0.9995:
case y >= 9.9995:
format = "%13.2f %s"
case y >= 0.09995:
case y >= 0.99995:
format = "%14.3f %s"
case y >= 0.009995:
case y >= 0.099995:
format = "%15.4f %s"
case y >= 0.0009995:
case y >= 0.0099995:
format = "%16.5f %s"
default:
case y >= 0.00099995:
format = "%17.6f %s"
default:
format = "%18.7f %s"
}
fmt.Fprintf(w, format, x, unit)
}

21
src/testing/benchmark_test.go
View file

@ -22,13 +22,14 @@ var prettyPrintTests = []struct {
{0, " 0 x"},
{1234.1, " 1234 x"},
{-1234.1, " -1234 x"},
{99.950001, " 100 x"},
{99.949999, " 99.9 x"},
{9.9950001, " 10.0 x"},
{9.9949999, " 9.99 x"},
{-9.9949999, " -9.99 x"},
{0.0099950001, " 0.0100 x"},
{0.0099949999, " 0.00999 x"},
{999.950001, " 1000 x"},
{999.949999, " 999.9 x"},
{99.9950001, " 100.0 x"},
{99.9949999, " 99.99 x"},
{-99.9949999, " -99.99 x"},
{0.000999950001, " 0.001000 x"},
{0.000999949999, " 0.0009999 x"}, // smallest case
{0.0000999949999, " 0.0001000 x"},
}
func TestPrettyPrint(t *testing.T) {
@ -50,13 +51,13 @@ func TestResultString(t *testing.T) {
if r.NsPerOp() != 2 {
t.Errorf("NsPerOp: expected 2, actual %v", r.NsPerOp())
}
if want, got := " 100\t 2.40 ns/op", r.String(); want != got {
if want, got := " 100\t 2.400 ns/op", r.String(); want != got {
t.Errorf("String: expected %q, actual %q", want, got)
}
// Test sub-1 ns/op (issue #31005)
r.T = 40 * time.Nanosecond
if want, got := " 100\t 0.400 ns/op", r.String(); want != got {
if want, got := " 100\t 0.4000 ns/op", r.String(); want != got {
t.Errorf("String: expected %q, actual %q", want, got)
}
@ -130,7 +131,7 @@ func TestReportMetric(t *testing.T) {
}
// Test stringing.
res.N = 1 // Make the output stable
want := " 1\t 12345 ns/op\t 0.200 frobs/op"
want := " 1\t 12345 ns/op\t 0.2000 frobs/op"
if want != res.String() {
t.Errorf("expected %q, actual %q", want, res.String())
}