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float16 trunc doesn't work for certain input #15993

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yuyichao opened this issue Apr 21, 2016 · 2 comments
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float16 trunc doesn't work for certain input #15993

yuyichao opened this issue Apr 21, 2016 · 2 comments
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test This change adds or pertains to unit tests

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@yuyichao
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Happened on AppVeyor win64 for #15984 (https://ci.appveyor.com/project/JuliaLang/julia/build/1.0.726/job/qux4bbryj4uuf9ts)

Basically the test doesn't work for any input with fractional larger than 0.99975586.

julia> x = 0.99975586f0
0.99975586f0

julia> trunc(Int,Float16(x)) == trunc(Int,x)
false

julia> Float16(x)
Float16(1.0)

julia> trunc(Int,x)
0

I'm not sure if the impl is wrong or the test is wrong. @kshyatt
@yuyichao yuyichao added the test This change adds or pertains to unit tests label Apr 21, 2016
@yuyichao yuyichao mentioned this issue Apr 21, 2016
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@yuyichao
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Assuming the Float16 constructor use the default RoundNearest in this case I guess the test is wrong here...

yuyichao added a commit that referenced this issue Apr 21, 2016
@yuyichao
Fix float16 test
6612826 
Do not use `rand()` and test both round up and down in different functions.

Closes #15993
@yuyichao yuyichao mentioned this issue Apr 21, 2016
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@tkelman
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tkelman commented Apr 22, 2016

Yeah, the test is wrong. I think this has come up before.

tkelman pushed a commit that referenced this issue Jun 17, 2016
@yuyichao @tkelman
Fix float16 test
3846eb4 
Do not use `rand()` and test both round up and down in different functions.

Closes #15993

(cherry picked from commit 6612826)
ref #15994
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@yuyichao @tkelman