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Test failure: System.Tests.DoubleTests.AtanPiTest on Android #71252
Description
Started failing on 6/22 in every Rolling run -- 7 failures in last 7 days
- 6/29: 14 failures in last 7 days
Affected test:
- System.Tests.DoubleTests.AtanPiTest
Platform:
- net7.0-Android-Release-x86-Mono_Release-Ubuntu.1804.Amd64.Android.29.Open
Failure:
Assert.Equal() Failure
Expected: -0.0
Actual: +0.0
at System.AssertExtensions.Equal(Double expected, Double actual, Double variance) in /_/src/libraries/Common/tests/TestUtilities/System/AssertExtensions.cs:line 747
at System.Tests.DoubleTests.AtanPiTest(Double value, Double expectedResult, Double allowedVariance) in /_/src/libraries/System.Runtime/tests/System/DoubleTests.cs:line 1475
at System.Reflection.MethodInvoker.InterpretedInvoke(Object obj, Span`1 args, BindingFlags invokeAttr)
Activity
[-]Test failure: System.Tests.DoubleTests.AtanPiTest[/-][+]Test failure: System.Tests.DoubleTests.AtanPiTest on Android[/+]karelz commentedon Jun 24, 2022
Due to large impact on CI, we should disable the tests ASAP
dotnet#71252 disable AtanPiTest for android x86
dakersnar commentedon Jun 24, 2022
Investigating this now. I am not able to reproduce it locally on a non-android device. I immediately notice that AtanPi uses the Math.Atan() intrinsic, which could have incorrect behavior on android devices. What this boils down to is that we expect Atan(-0) to produce -0, but instead it is probably producing 0. I'm unsure if there is a flaw in our logic or a flaw in the intrinsic's behavior.
dakersnar commentedon Jun 24, 2022
Here is the current implementation of AtanPi:
return Math.Atan(x) / Pi;We have a test verifying that
Math.Atan(-0)returns -0. A simple example also shows that -0 divided by Pi should return -0. Given this, I believe that there is a bug in Mono forMath.AtanPi.I'm unsure which mono area this should fall under so I'm putting it under "meta".
dotnet#71252 added comment
dotnet#71252 disable AtanPiTest on Android x86
dotnet#71252 disable only for android x86
dotnet#71252 refactor
#71252 disable Atan2PiTest on Android x86 (#71382)