The result of Math.log(3.0) is different on x86_64 and aarch64?
huangtianhua223 at gmail.com
Thu Jul 25 09:54:15 UTC 2019
In fact, we found the differences when we took tests of apache/spark, there
are some related tests failed.
And till now we also found the results for 'power' function is different
between x86_64 and aarch64 for some cases, for an example:
scala> import java.lang.Math._ import java.lang.Math._ scala>
abs(-83028485) res3: Int = 83028485 scala> var a = -83028485 a: Int =
-83028485 scala> abs(a) res4: Int = 83028485 scala> math.log(abs(a)) res5:
Double = 18.234694299654787 scala> pow(10, math.log(abs(a))) res6: Double =
scala> var a = -83028485 a: Int = -83028485 scala> abs(a) res38: Int =
83028485 scala> math.log(abs(a)) res39: Double = 18.234694299654787 scala>
pow(10, math.log(abs(a))) res40: Double = *1.71669957511859558E18*
So the algorithm of these math functions(power, log, maybe there are
others) is different on platforms? How or where I can find these
information? Could anyone help us? Thank you very much.
I don't know the behavior is correct or not, or maybe the tests of spark is
On Thu, Jul 25, 2019 at 4:11 PM Tianhua huang <huangtianhua223 at gmail.com>
> Sorry to disturb you again, I took some tests of java.lang.Math.log
> function on aarch64 server, I met a strange case, the result of
> Math.log(3.0) is different with x86_64:
> on x86_64:
> scala> Math.log(3.0) res50: Double = 1.0986122886681098
> but on aarch64:
> scala> Math.log(3.0) res19: Double = 1.0986122886681096
> Then I tried Math.log(4.0), Math.log(5.0) and some other numbers, the
> results on x86_64 and aarch64 are same, why Math.log(3.0) is so special?
> this confused me much, I think the result of
> Math.log(Double) should be same across platforms, right?
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