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[4.2-04-30-2018] Two small tweaks to Random test. #16524

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Merged
merged 2 commits into from
May 11, 2018
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[4.2-04-30-2018] Two small tweaks to Random test. #16524

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7e4a16c
[test] Float80 only exists on some platforms.
huonw May 11, 2018
57f7046
[test] Non-determinism down to 0.999999 (1-in-a-million) rather than …
huonw May 10, 2018
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13 changes: 10 additions & 3 deletions validation-test/stdlib/Random.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -128,7 +128,9 @@ func floatingPointRangeTest<T: BinaryFloatingPoint>(_ type: T.Type)
RandomTests.test("random floating points in ranges") {
floatingPointRangeTest(Float.self)
floatingPointRangeTest(Double.self)
#if !os(Windows) && (arch(i386) || arch(x86_64))
floatingPointRangeTest(Float80.self)
#endif
}

// Random Elements from collection
Expand Down Expand Up @@ -233,13 +235,18 @@ RandomTests.test("different random number generators") {
func chi2Test(_ samples: [Double]) -> Bool {
precondition(samples.count == 50, "confidence interval requires 50 samples")
let expected = samples.reduce(0, +) / Double(samples.count)
let cvLow = 23.983 // 0.1% with a degree of freedom of (50 - 1)
let cvHigh = 85.351 // 99.9% with a degree of freedom of (50 - 1)
// Right tail for 0.0001% (1e-6) with a degree of freedom of (50 -
// 1). With hundreds of builds a day, this has to be very low to not get too
// many spurious failures, but obvious problems should still be detected
// (e.g. an off-by-one that means samples[0] == 0 will result in chi2 =
// (0-expected)**2/expected + ... > expected, so as long as we've generated
// more than samples.count * cvHigh (~5500) values, we'll catch it).
let cvHigh = 111.1
let chi2 = samples.map {
(($0 - expected) * ($0 - expected)) / expected
}.reduce(0, +)

if chi2 < cvLow || chi2 > cvHigh {
if chi2 > cvHigh {
return false
}else {
return true
Expand Down