Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>Using Java's system time is not a good way to get a real benchmark. I refactored your code to use <a href="http://code.google.com/p/caliper/" rel="nofollow">Google Caliper</a> (which warms up the JVM, among other things)... and discovered similar results to you. Commenters correctly pointed out my original version was not good and that most of the time was going to <code>System.out.println</code> calls.</p> <p>Like I said, writing a benchmark is hard. Updated below is the new, correct version.</p> <h2>Results:</h2> <pre><code> 0% Scenario{vm=java, trial=0, benchmark=HashMap} 51.04 ns; σ=0.22 ns @ 3 trials 50% Scenario{vm=java, trial=0, benchmark=Array} 4.05 ns; σ=0.01 ns @ 3 trials benchmark ns linear runtime HashMap 51.04 ============================== Array 4.05 == </code></pre> <h2>Code:</h2> <pre><code>import com.google.caliper.Runner; import com.google.caliper.SimpleBenchmark; public class PerfTest { public static double hashNum = 0; public static double arrayNum = 0; public static class PerfBenchmark extends SimpleBenchmark { static java.util.HashMap&lt;String, Double&gt; map; static Double[] array = {1.0,2.0,3.0,4.0,5.0,6.0,7.0,8.0,9.0,10.0}; static{ map = new java.util.HashMap&lt;String, Double&gt;(); map.put("1", new Double(1)); map.put("2", new Double(2)); map.put("3", new Double(3)); map.put("4", new Double(4)); map.put("5", new Double(5)); map.put("6", new Double(6)); map.put("7", new Double(7)); map.put("8", new Double(8)); map.put("9", new Double(9)); map.put("10", new Double(10)); } public void timeHashMap(int nTimes){ int sz = map.size(); String key = "1"; for (int i=0; i &lt;nTimes; i++){ double sum = 0; for (int j =1; j&lt;=sz; j++){ sum += map.get(key); } hashNum += sum; } } public void timeArray(int nTimes){ for (int i=0; i &lt;nTimes; i++){ double sum = 0; for (int j=0; j&lt; array.length; j++) { sum += array[j]; } arrayNum += sum; } } } public static void main(String[] args){ Runner.main(PerfBenchmark.class, new String[0]); System.out.println(hashNum); System.out.println(arrayNum); } } </code></pre>
    singulars
    1. This table or related slice is empty.
    1. POJava: why Array (w index) *order of magnitude* faster than Map (key) access?
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USdurron597
    1. USdurron597
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. POJava: why Array (w index) *order of magnitude* faster than Map (key) access?
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. COAren't you benchmarking printing to System.out with that code?
      singulars
      1. PO
      1. USmeriton
    2. CO@meriton: Both versions do the same math and do the same print. You have to do *something* with the sum or the JVM realizes (it's pretty smart) the summing doesn't actually do anything and then doesn't perform it at all
      singulars
      1. PO
      1. USdurron597
    3. COWouldn't a println per benchmark (rather than a println per iteration) be sufficient for that?
      singulars
      1. PO
      1. USmeriton
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload