Mastering High Performance with Kotlin

The pitfalls of loops

There are a lot of optimizations related to loops. Let's investigate one more JMH example (http://hg.openjdk.java.net/code-tools/jmh/file/ef50cc696984/jmh-samples/src/main/java/org/openjdk/jmh/samples/JMHSample_11_Loops.java), which measures how much time it takes to sum two integers:

@State(Scope.Thread)@BenchmarkMode(Mode.AverageTime)@OutputTimeUnit(TimeUnit.NANOSECONDS)public class MyBenchmark {    int x = 1;    int y = 2;        @Benchmark    public int measureRight() {        return (x + y);    }        private int reps(int reps) {        int s = 0;        for (int i = 0; i < reps; i++) {            s += (x + y);        }        return s;    }        @Benchmark    @OperationsPerInvocation(1)    public int measureWrong_1() {        return reps(1);    }    @Benchmark    @OperationsPerInvocation(10)    public int measureWrong_10() ...