feat: JMHExample10

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));
+    }
+}