CODEWITHSUNDEEP
javaperformance
Tomáš Mocek
Tomáš Mocek

Reputation: 398

x*x vs Math.pow(x,2) java performance

I have done some testing about whether x*x or Math.pow(x, 2) is faster in Java. I was expecting simple x*x to be somewhat faster, however, it turned out that its about equally fast. Can someone enlighten me, how is that possible, please?

Upvotes: 12

Views: 10316

Answers (3)

apangin
apangin

Reputation: 98640

how is that possible, please

Because Math.pow is JVM intrinsic, that is, JIT-compiler inlines the call. Furthermore, when it sees that exponent is a constant 2, it replaces the call with exactly x*x.

Proof from HotSpot sources

Upvotes: 55

Davide Lorenzo MARINO
Davide Lorenzo MARINO

Reputation: 26956

The internal implementation of Math.pow() is delegated to a native function so it could be reasonable for a good performance. In any case to have valid test results you have to test the time in a loop to have an execution time realistic.

Upvotes: 2

Kayaman
Kayaman

Reputation: 73578

For all you know it's JITted (or even already in compile-time) down to the same exact thing. These kinds of micro-benchmarks rarely give very usable results, since there is no real context.

It's definitely not a reason to prefer one over another, since real world code rarely has a simple x^2 operation as a performance hotspot.

Upvotes: -2

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