Fix float64 comparison test failure on archs using FMA

prometheus/histogram_test.go

@@ -28,6 +28,8 @@ import (
 	"github.com/golang/protobuf/proto"
 	"google.golang.org/protobuf/types/known/timestamppb"
 
+	"github.com/prometheus/client_golang/prometheus/internal"
+
 	dto "github.com/prometheus/client_model/go"
 )
 
@@ -355,13 +357,12 @@ func TestBuckets(t *testing.T) {
 
 	got = ExponentialBucketsRange(1, 100, 10)
 	want = []float64{
-		1.0, 1.6681005372000588, 2.782559402207125,
-		4.641588833612779, 7.742636826811273, 12.915496650148842,
-		21.544346900318846, 35.93813663804629, 59.94842503189414,
-		100.00000000000007,
+		1.0, 1.6681, 2.7825, 4.6415, 7.7426, 12.9154, 21.5443,
+		35.9381, 59.9484, 100.0000,
 	}
-	if !reflect.DeepEqual(got, want) {
-		t.Errorf("exponential buckets range: got %v, want %v", got, want)
+	const epsilon = 0.0001
+	if !internal.AlmostEqualFloat64s(got, want, epsilon) {
+		t.Errorf("exponential buckets range: got %v, want %v (epsilon %f)", got, want, epsilon)
 	}
 }
 

prometheus/internal/almost_equal.go

@@ -0,0 +1,60 @@
+// Copyright (c) 2015 Björn Rabenstein
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+//
+// The code in this package is copy/paste to avoid a dependency. Hence this file
+// carries the copyright of the original repo.
+// https://github.com/beorn7/floats
+package internal
+
+import (
+	"math"
+)
+
+// minNormalFloat64 is the smallest positive normal value of type float64.
+var minNormalFloat64 = math.Float64frombits(0x0010000000000000)
+
+// AlmostEqualFloat64 returns true if a and b are equal within a relative error
+// of epsilon. See http://floating-point-gui.de/errors/comparison/ for the
+// details of the applied method.
+func AlmostEqualFloat64(a, b, epsilon float64) bool {
+	if a == b {
+		return true
+	}
+	absA := math.Abs(a)
+	absB := math.Abs(b)
+	diff := math.Abs(a - b)
+	if a == 0 || b == 0 || absA+absB < minNormalFloat64 {
+		return diff < epsilon*minNormalFloat64
+	}
+	return diff/math.Min(absA+absB, math.MaxFloat64) < epsilon
+}
+
+// AlmostEqualFloat64s is the slice form of AlmostEqualFloat64.
+func AlmostEqualFloat64s(a, b []float64, epsilon float64) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	for i := range a {
+		if !AlmostEqualFloat64(a[i], b[i], epsilon) {
+			return false
+		}
+	}
+	return true
+}