存储一个图的内存开销

100万点，10万边。

邻接表存法：

HashMap<Integer, HashSet<Integer>>的做法就不说了，这个最吃内存，开销肯定最大。

其余的：

3倍整型数组
Total Memory = 127991808 Used Memory = 669,888
Total Memory = 127991808 Used Memory = 13,339,680


public class Vertex{
public int id ; //顶点值
public int start ; //edges数组中边的起始位置
public int edgeNo; //该顶点的边数目

public Vertex(){

}

public Vertex( int iD, int x, int y){
id = iD;
start = x ;
edgeNo = y ;
}

Vertices数组:
Vertex[] vertices = new Vertex[1000000] ;
int[] edges = new int[100000] ;
for(int i =0; i<vertices.length ;i++ ){
vertices[i] = new Vertex(0,i,0);
}
for(int i =0; i<edges.length ;i++ ){
edges[i] = i ;
}

Total Memory = 127991808 Used Memory = 669,888
Total Memory = 127991808 Used Memory = 29,368,024


public String toString(){
return new String(id+":"+start+","+edgeNo) ;
}
}
Vertices数组链表ArrayList:
Total Memory = 127991808 Used Memory = 669888
Total Memory = 127991808 Used Memory = 34929568

package memoryTestForIncBSP;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.util.ArrayList;

import mergeTest.Vertex;

public class MemoryTest {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		Runtime rt = Runtime.getRuntime();  
	        System.out.println("Total Memory = " + rt.totalMemory() + " Used Memory = " + (rt.totalMemory() - rt.freeMemory()));  
	        
//	        Vertex[] vertices = new Vertex[1000000] ;
//	        int[] edges = new int[100000] ;
//	        for(int i =0; i<vertices.length ;i++ ){
//	        	vertices[i] = new Vertex(0,i,0);
//	        }
//	        for(int i =0; i<edges.length ;i++ ){
//	        	edges[i] = i ;
//	        }
	        
	        ArrayList<Vertex> vertices = new ArrayList<Vertex>() ;
	        int[] edges = new int[100000] ;
	        for(int i =0; i<1000000 ;i++ ){
	        	vertices.add(new Vertex(0,i,0));
	        }
	        for(int i =0; i<edges.length ;i++ ){
	        	edges[i] = i ;
	        }
	        
//	        int[] vertices = new int[3000000] ; 
//	        int[] edges = new int[100000] ;
//	        for(int i =0; i<vertices.length ;i++ ){
//	        	vertices[i] = i;
//            }
//	        for(int i =0; i<edges.length ;i++ ){
//	        	edges[i] = i;
//            }
	        
    	      System.out.println("Total Memory = " + rt.totalMemory() + " Used Memory = " + (rt.totalMemory() - rt.freeMemory()));  
	}
}