diff --git a/multithreading1/src/main/java/cn/bunny/jmh/JMHExample10.java b/multithreading1/src/main/java/cn/bunny/jmh/JMHExample10.java new file mode 100644 index 0000000..a1e1729 --- /dev/null +++ b/multithreading1/src/main/java/cn/bunny/jmh/JMHExample10.java @@ -0,0 +1,56 @@ +package cn.bunny.jmh; + +import org.openjdk.jmh.annotations.*; +import org.openjdk.jmh.infra.Blackhole; +import org.openjdk.jmh.runner.Runner; +import org.openjdk.jmh.runner.RunnerException; +import org.openjdk.jmh.runner.options.Options; +import org.openjdk.jmh.runner.options.OptionsBuilder; + +import java.util.concurrent.TimeUnit; + +@BenchmarkMode(Mode.AverageTime) +@Fork(1) +@Warmup(iterations = 5) +@Measurement(iterations = 10) +@OutputTimeUnit(TimeUnit.MICROSECONDS) +@State(Scope.Thread) +public class JMHExample10 { + + double x1 = Math.PI; + double x2 = Math.PI * 2; + + public static void main(String[] args) throws RunnerException { + Options options = new OptionsBuilder() + .include(JMHExample10.class.getSimpleName()) + .build(); + new Runner(options).run(); + } + + @Benchmark + public double baseline() { + // 不是 Dead Code + return Math.pow(x1, x2); + } + + @Benchmark + public double powButReturnOne() { + // Dead Code 会被擦除 + Math.pow(x1, x2); + + // Dead Code 不会擦除,因为返回了 + return Math.pow(x1, x2); + } + + @Benchmark + public double powThenAdd() { + // 对两个结果都进行了计算,所以都会生效 + return Math.pow(x1, x2) + Math.pow(x1, x2); + } + + @Benchmark + public void useBlackWhole(Blackhole blackhole) { + blackhole.consume(Math.pow(x1, 2)); + blackhole.consume(Math.pow(x2, 2)); + } +}