如何测试使用考虑垃圾收集器的内存？

Question

我在测试排序算法，我想通过测试1000个随机向量来测试平均使用的内存。问题是当我在循环内部运行20个随机向量时，垃圾收集器运行并且我失去了计算。我该怎么做？我不想一个一个的测试手动= X。

for(int j = 0; j < 1000; j++) 
{ 
    int vetOriginal[] = Generate(); 
    for(int i = 0; i < 10; i++) 
    { 
     int vetParaTeste[] = vetOriginal.clone(); 
     long memoriaInicial = Runtime.getRuntime().freeMemory()/1024; 
     mergeSort(vetParaTeste); 
     somaMemoriaKB += memoriaInicial - Runtime.getRuntime().freeMemory()/1024; 
    } 
} 
System.out.println("Average memory used: " + somaMemoriaKB/(1000* 10)); 

Answer 1

OK，所以我有点晚了这里，你有可能已经解决了这个，但以防万一有人想知道，最简单的方法来阻止GC清理的目的是在另一个对象中保留对它的引用。对于您创建的每个对象，都将它添加到某种容器，如数组/散列/向量/列表或您的语言支持的任何对象。例如：

var items as Array[0..numberOfItems] 

for (var i = 0; i < numberOfItems; i++) { 
    var vector = createVector() 
    items[i] = vector; 
} 

容器会增加一些开销，所以您需要先测量它然后从最终输出中减去该数量。例如：

var baseMemory = measureMemory() 
var numberOfItems = 1000 

// create an array of a known size (eg 1000 bytes) 
var arrayOfKnownSize as Array[0..numberOfItems] 

for (var i = 0; i < numberOfItems; i++) 
    arrayOfKnownSize[i] = Int32(0xFF) 

// calculate the size occupied by just the data ... 
var expectedMemory = sizeOf(Int32) * numberOfItems 

// ... subtract this from the total memory usage and you will get the overhead 
var arrayOverhead = measureMemory() - baseMemory - expectedMemory 

// now measure the memory used by an array of vectors 
baseMemory = measureMemory() 
var vectors as Array[0..numberOfItems] 

for (var i = 0; i < numberOfItems; i++) { 
    var vector = createVector() 
    vectors[i] = vector; 
} 

// subtract the array overhead from the memory usage 
var usedMemory = measureMemory() - baseMemory - arrayOverhead 
var averageMemory = usedMemory/numberOfItems 

你会然后做相同的测量像你一样，每一个载体插入到一个数组中，并从内存使用量减去arrayOverhead，让您的最终结果。