binary search vs linear scan

BinarySearch.java

package com.databricks.unsafe.util.benchmark;

import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.Param;
import org.openjdk.jmh.annotations.Scope;
import org.openjdk.jmh.annotations.State;
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;

@State(Scope.Benchmark)
public class BinarySearch {

  @Param({"1", "10", "50", "100", "200", "250", "273", "365"})
  public int dayInYear;

  private static final int[] arr = {0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365};

  @Benchmark
  public long linearSearch() {
    if (dayInYear <= 31) {
      return 1;
    } else if (dayInYear <= 59) {
      return 2;
    } else if (dayInYear <= 90) {
      return 3;
    } else if (dayInYear <= 120) {
      return 4;
    } else if (dayInYear <= 151) {
      return 5;
    } else if (dayInYear <= 181) {
      return 6;
    } else if (dayInYear <= 212) {
      return 7;
    } else if (dayInYear <= 243) {
      return 8;
    } else if (dayInYear <= 273) {
      return 9;
    } else if (dayInYear <= 304) {
      return 10;
    } else if (dayInYear <= 334) {
      return 11;
    } else {
      return 12;
    }
  }

  @Benchmark
  public long binarySearch() {
    int index = java.util.Arrays.binarySearch(arr, dayInYear);
    return index > 0 ? index - 1 : - index - 2;  // zero based
  }

  public static void main(String[] args) throws RunnerException {
    Options opt = new OptionsBuilder()
      .include(BinarySearch.class.getSimpleName())
      .warmupIterations(5)
      .measurementIterations(5)
      .forks(2)
      .jvmArgs("-ea")
      .build();

    new Runner(opt).run();
  }
}

result

Benchmark                  (dayInYear)   Mode  Cnt          Score           Error  Units
BinarySearch.binarySearch            1  thrpt    4  115347880.155 ±   8520914.477  ops/s
BinarySearch.binarySearch           10  thrpt    4  113654466.772 ±   8625273.222  ops/s
BinarySearch.binarySearch           50  thrpt    4  133030684.937 ±  10710487.122  ops/s
BinarySearch.binarySearch          100  thrpt    4  133953770.632 ±  12634401.850  ops/s
BinarySearch.binarySearch          200  thrpt    4  130781158.940 ±   8043762.686  ops/s
BinarySearch.binarySearch          250  thrpt    4  132553717.324 ±  21414919.596  ops/s
BinarySearch.binarySearch          273  thrpt    4  244471672.528 ±   9463128.602  ops/s
BinarySearch.binarySearch          365  thrpt    4  166535896.580 ±  28047392.033  ops/s
BinarySearch.linearSearch            1  thrpt    4  463719441.329 ± 106581527.249  ops/s
BinarySearch.linearSearch           10  thrpt    4  448299356.497 ± 166163742.716  ops/s
BinarySearch.linearSearch           50  thrpt    4  449009750.056 ± 113741145.284  ops/s
BinarySearch.linearSearch          100  thrpt    4  443775770.080 ±  31449395.157  ops/s
BinarySearch.linearSearch          200  thrpt    4  395199721.525 ±  28370833.771  ops/s
BinarySearch.linearSearch          250  thrpt    4  322339256.287 ± 153877281.219  ops/s
BinarySearch.linearSearch          273  thrpt    4  351028964.278 ±  34651113.649  ops/s
BinarySearch.linearSearch          365  thrpt    4  324125219.514 ±  33060425.949  ops/s