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runtime: be a lot more lenient on smhasher avalanche test.

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Fixes #7943

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/98170043
This commit is contained in:
Keith Randall 2014-05-09 15:50:57 -07:00
parent e3eee85b0d
commit 711d1ad7ee
1 changed files with 3 additions and 3 deletions
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6
src/pkg/runtime/hash_test.go
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@ -397,10 +397,10 @@ func avalancheTest1(t *testing.T, k Key) {
// all sums inside those bounds with 99% probability.
N := n * hashSize
var c float64
// find c such that Prob(mean-c*stddev < x < mean+c*stddev)^N > .99
for c = 0.0; math.Pow(math.Erf(c/math.Sqrt(2)), float64(N)) < .99; c += .1 {
// find c such that Prob(mean-c*stddev < x < mean+c*stddev)^N > .9999
for c = 0.0; math.Pow(math.Erf(c/math.Sqrt(2)), float64(N)) < .9999; c += .1 {
}
c *= 2.0 // allowed slack - we don't need to be perfectly random
c *= 4.0 // allowed slack - we don't need to be perfectly random
mean := .5 * REP
stddev := .5 * math.Sqrt(REP)
low := int(mean - c*stddev)