Github user kiszk commented on the issue:
https://github.com/apache/spark/pull/19916
Thank you for checking Java bytecode. I am talking about native code, not
about bytecode. Hotspot compiler may eliminate statements.
I think that this elapsed time includes interpreter execution, JIT
compilation, and native code execution. It would be good to add warm-up.
I think that it is not the best to write a long-running loop in `main()`
method since it leads to on-stack-replacement. It would be good to put the
long-running target loop into a callee.
I think that it would be good to store a result into a global variable
unlikely to eliminate unused variables and related operations.
WDYT?
```
Integer globalVar g;
void targetMethod() {
Integer b;
for(long i = 0; i < 1000000000; ++ i){
b += ((Integer)a) + 1;
}
g = b;
}
// warm up
for (int i = 0; i < 10000000; i++) { targetMethod();}
long start = System.currentTimeMillis();
targetMethod();
long end = System.currentTimeMillis();}
```
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