jerolba

MemoryHistogram diff = Histogramer.getDiff(() -> {
    HashMap<Integer, String> map = new HashMap<>();
    for (int i = 0; i < 10000; i++) {
        map.put(i, "" + i);
    }
    return map;
});

HistogramEntry nodes = diff.get("java.util.HashMap$Node");

jerolba

Histogramer histogramer = new Histogramer();
MemoryHistogram histogram = histogramer.createHistogram();

HistogramEntry arrayList = histogram.get("java.util.ArrayList");
System.out.println(arrayList.getInstances());
System.out.println(arrayList.getSize());

for (HistogramEntry entry : histogram) {
    System.out.println(entry);
}

jerolba

public void memoryHistogram() {
    String name = ManagementFactory.getRuntimeMXBean().getName();
    String PID = name.substring(0, name.indexOf("@"));
    Process p = Runtime.getRuntime().exec("jcmd " + PID + " GC.class_histogram");
    try (BufferedReader input = new BufferedReader(new InputStreamReader(p.getInputStream()))) {
        input.lines().forEach(System.out::println);
    }
}

jerolba

+-------------+-----------+------------+--------------+---------------+---------------+
| Nº Products | Nº Stores |   Total    | TupleMap(ms) | Tuple new(ms) | DoubleMap(ms) |
+-------------+-----------+------------+--------------+---------------+---------------+
|       1,000 |       100 |    100,000 |        12.08 |         12.55 |          3.81 |
|       2,500 |       100 |    250,000 |        37.11 |         38.21 |         14.35 |
|       5,000 |       100 |    500,000 |        77.40 |         77.39 |         46.84 |
|       7,500 |       100 |    750,000 |       125.96 |        126.35 |         68.53 |
|      10,000 |       100 |  1,000,000 |       148.55 |        141.47 |        163.37 |
|       1,000 |       250 |    250,000 |        48.96 |         50.41 |         18.30 |
|       2,500 |       250 |    625,000 |       140.25 |        144.70 |         70.04 |

jerolba

+-------------+-----------+------------+--------------+---------------+
| Nº Products | Nº Stores |   Total    | TupleMap(ms) | DoubleMap(ms) |
+-------------+-----------+------------+--------------+---------------+
|       1,000 |       100 |    100,000 |         33.1 |          5.61 |
|       2,500 |       100 |    250,000 |       103.38 |         24.78 |
|       5,000 |       100 |    500,000 |       177.71 |        116.43 |
|       7,500 |       100 |    750,000 |       272.02 |        160.95 |
|      10,000 |       100 |  1,000,000 |       314.94 |        241.86 |
|       1,000 |       250 |    250,000 |       129.18 |         19.82 |
|       2,500 |       250 |    625,000 |       292.97 |        114.85 |

jerolba

+-----------------------------+-----------+-------------+
|            Class            | instances |    size     |
+-----------------------------+-----------+-------------+
| java.util.HashMap$Node      | 5.010.000 | 160.320.000 |
| java.util.HashMap$Node[]    |    10.001 |  41.185.552 |
| java.util.HashMap           |    10.001 |     480.048 |
| com.jerolba.bikey.DoubleMap |         1 |          16 |
+-----------------------------+-----------+-------------+

jerolba

+----------------------------+-----------+-------------+
|           Class            | instances |    size     |
+----------------------------+-----------+-------------+
| java.util.HashMap$Node     | 5.000.000 | 160.000.000 |
| com.jerolba.bikey.Tuple    | 5.000.000 | 120.000.000 |
| java.util.HashMap$Node[]   |         1 |  33.554.448 |
| java.util.HashMap          |         1 |          48 |
| com.jerolba.bikey.TupleMap |         1 |          16 |
+----------------------------+-----------+-------------+

jerolba

public class MyObjectKey {
    public int hashCode() {
        return (firstKey << 16) + secondKey;
    }
}

jerolba

for (int i = 0; i < n_products; i++) {
    for (int j = 0; j < n_stores; j++) {
        int hashValue = HashMap.hash(Objects.hash(i, j));
        histogram.add(hashValue);
    }
}

jerolba

static final int hash(Object key) {
    int h;
    return (key == null) ? 0 : (h = key.hashCode()) ^ (h >>> 16);
}