CUDA与Java速度比较---生成Julia数据集并画图

在《GPU编程CUDA实战》第45页有个Julia数据集，本文把这个CUDA的程序改成了java的，然后每个程序运行20次，统计时间，比较这两个程序那个快些。

java(ms)	c++(ms)
202	1904
269	1850
228	1737
242	1712
181	1770
222	1774
272	1733
295	1681
238	1320
282	1725
248	1833
294	1478
264	1692
176	1431
229	1479
230	1457
256	1645
193	1802
239	1208
230	1537
239.5	1638.4

结果是惊人的，java完成同样的计算任务用的时间只有CUDA的15%，就这道题来说Java的速度是CUDA的5.8倍.

CUDA程序

#include "book.h"
#include "cuda_runtime.h"
#include "cpu_bitmap.h"

#include<iostream>
#include <time.h>

using namespace std;


#define DIM 1000

/****************************************/

struct cuComplex {

float r;
float i;

__device__ cuComplex(float a,float b) : r(a),i(b) {}

__device__ float magnitude2(void){
return r*r+i*i;
}

__device__ cuComplex operator*(const cuComplex& a) {
return cuComplex(r*a.r-i*a.i, i*a.r+r*a.i);
}

__device__ cuComplex operator+(const cuComplex& a){


return cuComplex(r+a.r,i+a.i);
}

};


/***************************************/


__device__ int julia(int x ,int y){

const float scale =2;

 
float jx=scale*(float)(DIM/2-x)/(DIM/2);
float jy=scale*(float)(DIM/2-y)/(DIM/2);

cuComplex c(-0.8,0.156);
cuComplex a(jx,jy);

 int i=0;
 for(i=0 ;i<200; i++){
 
 a=a*a+c;
 
 if(a.magnitude2()>1000)
 return 0;
 }
 
 return 1;
 
 }
 
 
 
 
 __global__ void kernel(unsigned char *ptr){
 
 int x=blockIdx.x;
 int y=blockIdx.y;
 int offset=x+y*gridDim.x;
 
 int juliaValue=julia(x,y);
 
 ptr[offset*4+0]=255*juliaValue;
 ptr[offset*4+1]=0; 
 ptr[offset*4+2]=0;  
 ptr[offset*4+3]=255;
 
 }
 
 
 
 
 
 int main(void){
 
clock_t start,ends; 
start=clock();


 
 CPUBitmap bitmap(DIM,DIM);
 
 unsigned char *dev_bitmap;
 
 HANDLE_ERROR (cudaMalloc( (void**)&dev_bitmap,bitmap.image_size()));
 
 dim3 grid(DIM,DIM);
 

 
 
 kernel<<< grid,1>>>(dev_bitmap);
 
 HANDLE_ERROR (cudaMemcpy (bitmap.get_ptr(),dev_bitmap,bitmap.image_size(),cudaMemcpyDeviceToHost ));
                           
 ends=clock();
 cout<<(ends-start)*1000/CLOCKS_PER_SEC <<endl;                       
                           
 bitmap.display_and_exit();
 
 
 
 HANDLE_ERROR (cudaFree(dev_bitmap));
 

 
 }

Java程序

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.io.FileWriter;
import java.io.IOException;
import java.text.DecimalFormat;

import javax.swing.JFrame;
import javax.swing.JPanel;

public class julia1 extends JFrame {
	
	
	 MyPanedrawjulia1 mp = null ;   //1
 
	    public static void main(String[] args)   
	    {  
	    	long sysDate1 = System.currentTimeMillis();
	    	
	    	julia1 qwe = new julia1();  //2
	    	

			  long sysDate2 = System.currentTimeMillis();

			  System.out.println(sysDate2-sysDate1 );
	    }  
	      
	    public julia1()  //3
	    {  
	        mp = new MyPanedrawjulia1();  //4
	          
	        this.add(mp);  
	        
	        this.setSize(3000,2000);  
	        this.setVisible(true);  
	        
	        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);  
	    }  
	}  
	  
	class MyPanedrawjulia1 extends JPanel    //用于绘图和实现绘图区域   //5
	{  
		 
		
	    public void paint(Graphics g)  
	    {  
	          
	        super.paint(g);     
	        
	        
	        try {
	        	
	        	
				julia(   g );
				

				  
			} catch (IOException e1) {
		 
				e1.printStackTrace();
			}
	        
	        

			 
	       
	    }
	    
 

	private void julia(Graphics g) throws IOException

	{
		
		
		
		g.setFont(new Font("宋体",Font.BOLD,20));
		
		int dim=1000;
		
		double c=-0.8;
		double d=0.156;
		
		double rate=1.6;
		
 
		
		DecimalFormat df = new DecimalFormat( "0.0000000000");
		
		for(double a=1 ;a<1000;a++)
		{
	
			for(double b=1 ;b<1000;b++)
			{

				 
				double p1=rate*(dim/2-a)/(dim/2);
				double p2=rate*(dim/2-b)/(dim/2);
				
 		 
				
				double sum=0;
				
		for(  int n=0 ;n<200;n++   )
		{
			 double r1=0.0;
			 double r2=0.0;
			 
			r1=Math.pow(p1, 2)-Math.pow(p2, 2)+c;
			r2=2*p1*p2+d;
			
			p1=r1;
			p2=r2;
			
		 
			sum=sum+(Math.pow(p1, 2)+Math.pow(p2, 2));
			
			if (sum>1000)
			{
				break;
			}
			

			
		}
		
		if(sum<1000)
		{
			 
			
			//System.out.println(a+"  *****  "+b +"   "+sum+"  "  );
			
			  g.setColor(Color.red); 
			
			g.drawOval((int)(a), (int)(b),2, 2);

		}
		
		/*************************************************/
	 
		
	
		}
			
			
			
			 
		}
		
		 
		 
		

 
		 
	}	


	
	}  

CUDA生成图片

Java生成图片