benchstat: don't print sign for 0% when there is no change
When all samples are identical, instead of printing
+0.00%, print just 0.00%.
This is not just more accurate.
When benchmarking the compiler, one item of interest
is the impact on object file and executable sizes.
These can change by tiny amounts, below two sig figs.
However, the existence of any change is sometimes a cue
to the reader to investigate further.
This obviously should not be relied on,
but it is nevertheless a useful signal.
Change-Id: I1e5157a52fc47c6871ca87b0e9cff223f4fd43d9
Reviewed-on: https://go-review.googlesource.com/44190
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/benchstat/table.go b/benchstat/table.go
index ef938d1..cd8a027 100644
--- a/benchstat/table.go
+++ b/benchstat/table.go
@@ -99,12 +99,16 @@
} else if testerr != nil {
row.Note = fmt.Sprintf("(%s)", testerr)
} else if pval < alpha {
- pct := ((new.Mean / old.Mean) - 1.0) * 100.0
- row.Delta = fmt.Sprintf("%+.2f%%", pct)
- if pct < 0 == (table.Metric != "speed") { // smaller is better, except speeds
- row.Change = +1
+ if new.Mean == old.Mean {
+ row.Delta = "0.00%"
} else {
- row.Change = -1
+ pct := ((new.Mean / old.Mean) - 1.0) * 100.0
+ row.Delta = fmt.Sprintf("%+.2f%%", pct)
+ if pct < 0 == (table.Metric != "speed") { // smaller is better, except speeds
+ row.Change = +1
+ } else {
+ row.Change = -1
+ }
}
}
if row.Note == "" && pval != -1 {
diff --git a/cmd/benchstat/main_test.go b/cmd/benchstat/main_test.go
index 4653ae0..4a50020 100644
--- a/cmd/benchstat/main_test.go
+++ b/cmd/benchstat/main_test.go
@@ -39,6 +39,7 @@
check(t, "packagesold", "packagesold.txt")
check(t, "packages", "packagesold.txt", "packagesnew.txt")
check(t, "units", "units-old.txt", "units-new.txt")
+ check(t, "zero", "-delta-test=none", "zero-old.txt", "zero-new.txt")
}
func check(t *testing.T, name string, files ...string) {
diff --git a/cmd/benchstat/testdata/zero-new.txt b/cmd/benchstat/testdata/zero-new.txt
new file mode 100644
index 0000000..d855b6b
--- /dev/null
+++ b/cmd/benchstat/testdata/zero-new.txt
@@ -0,0 +1,4 @@
+pkg: synthetic
+note: test benchstat printing of zeros
+
+BenchmarkImperceptible 1 1234567890 a-bytes 171717171716 b-bytes 99999930 c-bytes
diff --git a/cmd/benchstat/testdata/zero-old.txt b/cmd/benchstat/testdata/zero-old.txt
new file mode 100644
index 0000000..9df0d06
--- /dev/null
+++ b/cmd/benchstat/testdata/zero-old.txt
@@ -0,0 +1,4 @@
+pkg: synthetic
+note: test benchstat printing of zeros
+
+BenchmarkImperceptible 1 1234567890 a-bytes 171717171717 b-bytes 99999929 c-bytes
diff --git a/cmd/benchstat/testdata/zero.golden b/cmd/benchstat/testdata/zero.golden
new file mode 100644
index 0000000..7c6170f
--- /dev/null
+++ b/cmd/benchstat/testdata/zero.golden
@@ -0,0 +1,8 @@
+name old a-bytes new a-bytes delta
+Imperceptible 1.23GB ± 0% 1.23GB ± 0% 0.00%
+
+name old b-bytes new b-bytes delta
+Imperceptible 172GB ± 0% 172GB ± 0% -0.00%
+
+name old c-bytes new c-bytes delta
+Imperceptible 100MB ± 0% 100MB ± 0% +0.00%
