Why is long slower than int in x64 Java?

Question

I\'m running Windows 8.1 x64 with Java 7 update 45 x64 (no 32 bit Java installed) on a Surface Pro 2 tablet.

The code below takes 1688ms when the type of i is a long

Answer 1

Basic unit of data in a Java Virtual Machine is word. Choosing the right word size is left upon the implementation of the JVM. A JVM implementation should choose a minimum word size of 32 bits. It can choose a higher word size to gain efficiency. Neither there is any restriction that a 64 bit JVM should choose 64 bit word only.

The underlying architecture doesn't rules that the word size should also be the same. JVM reads/writes data word by word. This is the reason why it might be taking longer for a long than an int.

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