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improve handling of negative bounds in histogram std dev/var 

Signed-off-by: Jeanette Tan <jeanette.tan@grafana.com>
This commit is contained in:
Jeanette Tan 2024-03-22 03:42:50 +08:00 committed by beorn7
parent 9d32754bc0
commit 22d0f4f114
2 changed files with 9 additions and 3 deletions
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6
promql/engine_test.go
View File

@ -3496,7 +3496,7 @@ func TestNativeHistogram_HistogramStdDevVar(t *testing.T) {
},
NegativeBuckets: []int64{1, 0},
},
stdVar: 1544.8582535368798, // actual variance: 1738.4082
stdVar: 1844.4651144196398, // actual variance: 1738.4082
},
{
name: "-100000, -10000, -1000, -888, -888, -100, -50, -9, -8, -3",
@ -3514,7 +3514,7 @@ func TestNativeHistogram_HistogramStdDevVar(t *testing.T) {
},
NegativeBuckets: []int64{1, 0, 0, 0, 0, 2, -2, 0},
},
stdVar: 1240930974.5260057, // actual variance: 882690990
stdVar: 759352122.1939945, // actual variance: 882690990
},
{
name: "-10 x10",
@ -3528,7 +3528,7 @@ func TestNativeHistogram_HistogramStdDevVar(t *testing.T) {
},
NegativeBuckets: []int64{10},
},
stdVar: 454.2741699796952, // actual variance: 0
stdVar: 1.725830020304794, // actual variance: 0
},
{
name: "-50, -8, 0, 3, 8, 9, 100, NaN",

6
promql/functions.go
View File

@ -1116,6 +1116,9 @@ func funcHistogramStdDev(vals []parser.Value, args parser.Expressions, enh *Eval
val = 0
} else {
val = math.Sqrt(bucket.Upper * bucket.Lower)
if bucket.Upper < 0 {
val = -val
}
}
delta := val - mean
variance, cVariance = kahanSumInc(bucket.Count*delta*delta, variance, cVariance)
@ -1149,6 +1152,9 @@ func funcHistogramStdVar(vals []parser.Value, args parser.Expressions, enh *Eval
val = 0
} else {
val = math.Sqrt(bucket.Upper * bucket.Lower)
if bucket.Upper < 0 {
val = -val
}
}
delta := val - mean
variance, cVariance = kahanSumInc(bucket.Count*delta*delta, variance, cVariance)