Low GC in Java: Using primitives

Overview

In a recent article I examined how using primitives and collections which support primitives natively instead of Wrappers and standard collections can reduce memory usage and improve performance.

Different way to have a Map of int/Integer

There are a number of ways you can use int/Integer and a number of collections you store them in. Depending on which approach you use can have a big difference on the performance and the amount of garbage produced.
TestPerformance RangeMemory used
Use Integer wrappers and HashMap71 - 134 (ns) 53 MB/sec
Use int primitives and HashMap45 - 76 (ns)36 MB/sec
Use int primitives and FastMap58 - 93 (ns)28 MB/sec
Use int primitives and TIntIntHashMap18 - 28 (ns) nonimal
Use int primitives and simple hash map6 - 9 (ns) nonimal
The performance range was the typical (50%tile) and one of the higher (98%tile) timings. The garbage was the result of 900,000 loops per second.


These tests were run on my new system.


The Code

Loop tested
int runs = 300 * 300;
for (int i = 0; i < runs; i++) {
    int x = i % 300;
    int y = i / 300;
    int times = x * y;
    Integer count = counters.get(times);
    if (count == null)
        counters.put(times, 1);
    else
        counters.put(times, count + 1);
}

Link to all the code is here

Directory of performance examples

Comments

  1. akoskm12 July 2011 at 05:02

    Hi!
    I found your article very interesting.
    What do you mean by "Use int primitives and simple hash map", did you implemented your own Hash Map functions?

    ReplyDelete
  2. Peter Lawrey12 July 2011 at 08:26

    @akoskm, Yes, the simple HashMap implements just what is required for the test. Its code in in the "Directory of performance examples" link, or you can click SimpleHashMap

    ReplyDelete

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