在《GPU編程CUDA實(shí)戰(zhàn)》第45頁(yè)有個(gè)Julia數(shù)據(jù)集，本文把這個(gè)CUDA的程序改成了java的，然后每個(gè)程序運(yùn)行20次，統(tǒng)計(jì)時(shí)間，比較這兩個(gè)程序那個(gè)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

結(jié)果是驚人的，java完成同樣的計(jì)算任務(wù)用的時(shí)間只有CUDA的15%，就這道題來(lái)說(shuō)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 ; //1public static void main(String[] args) { long sysDate1 = System.currentTimeMillis();julia1 qwe = new julia1(); //2long sysDate2 = System.currentTimeMillis();System.out.println(sysDate2-sysDate1 );} public julia1() //3{ mp = new MyPanedrawjulia1(); //4this.add(mp); this.setSize(3000,2000); this.setVisible(true); this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); } } class MyPanedrawjulia1 extends JPanel //用于繪圖和實(shí)現(xiàn)繪圖區(qū)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("宋體",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生成圖片

Java生成圖片

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