mirror of
https://github.com/prometheus/prometheus.git
synced 2024-11-09 23:24:05 -08:00
d550c4a0b9
At first it wasn't obvious to me why the first check would give a different result to the second. Signed-off-by: Bryan Boreham <bjboreham@gmail.com>
52 lines
1.6 KiB
Go
52 lines
1.6 KiB
Go
// Copyright 2024 The Prometheus Authors
|
|
// Licensed under the Apache License, Version 2.0 (the "License");
|
|
// you may not use this file except in compliance with the License.
|
|
// You may obtain a copy of the License at
|
|
//
|
|
// http://www.apache.org/licenses/LICENSE-2.0
|
|
//
|
|
// Unless required by applicable law or agreed to in writing, software
|
|
// distributed under the License is distributed on an "AS IS" BASIS,
|
|
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
// See the License for the specific language governing permissions and
|
|
// limitations under the License.
|
|
|
|
package almost
|
|
|
|
import (
|
|
"math"
|
|
|
|
"github.com/prometheus/prometheus/model/value"
|
|
)
|
|
|
|
var minNormal = math.Float64frombits(0x0010000000000000) // The smallest positive normal value of type float64.
|
|
|
|
// Equal returns true if a and b differ by less than their sum
|
|
// multiplied by epsilon, or if both are StaleNaN, or if both are any other NaN.
|
|
func Equal(a, b, epsilon float64) bool {
|
|
// StaleNaN is a special value that is used as staleness maker, and
|
|
// we don't want it to compare equal to any other NaN.
|
|
if value.IsStaleNaN(a) || value.IsStaleNaN(b) {
|
|
return value.IsStaleNaN(a) && value.IsStaleNaN(b)
|
|
}
|
|
|
|
// NaN has no equality but for testing we still want to know whether both values
|
|
// are NaN.
|
|
if math.IsNaN(a) && math.IsNaN(b) {
|
|
return true
|
|
}
|
|
|
|
// Cf. http://floating-point-gui.de/errors/comparison/
|
|
if a == b {
|
|
return true
|
|
}
|
|
|
|
absSum := math.Abs(a) + math.Abs(b)
|
|
diff := math.Abs(a - b)
|
|
|
|
if a == 0 || b == 0 || absSum < minNormal {
|
|
return diff < epsilon*minNormal
|
|
}
|
|
return diff/math.Min(absSum, math.MaxFloat64) < epsilon
|
|
}
|