sqrt1.cpp

单片机的一个开平方算法,是个工程包,很实用.

// sqrt1.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include "sqrt1.h"
#include <math.h>

#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif

/////////////////////////////////////////////////////////////////////////////
// The one and only application object

CWinApp theApp;

float G_SqrtTable[262144];
long G_SqrtTable1[262144];

using namespace std;

unsigned long SquareRoot(unsigned long nSquare)
{
    unsigned long nRoot, nTest=1;
    do
    {
        nRoot = nTest;
        nTest = (nSquare/nRoot+nRoot) >> 1;
    } while ((nTest - nRoot > 1) || (nRoot - nTest > 1));
         //while ((nTest >> 1) != (nRoot >> 1));
    return nRoot;
}

long sqrt1(long xk)//开平方函数
{
	long y1,y0;
	y1=0;
	y0=0;
	if(xk<0)
		return 0;
	else if(xk==0 || xk==1) 
		return xk;
	y0=xk;
	while(1)
	{
		y1=y0/2+xk/(2*y0);
		if(y1>(y0-2) && y1<(y0+1))
			break;
		else 
			y0=y1;
	}
	return y1;
}//end

float kf(float shu)
{
	float a,b,i;
	a=shu/2;
	for(i=1;i<100;i++)
	{ 
		b=a-(a*a-shu)/(2*a);
		a=b;
	}
	return a;
}



float sqrt2(DWORD tk)//开平方函数
{
//	if(xk<256)
		return G_SqrtTable[tk];
//	int m = 12;
//	DWORD tk = xk;
//	while (/*0 == */!(tk & 0xC0000000))
//	{
//		tk = tk<<2;
//		m--;
//	}
	//DWORD sk = tk >> 24;

//	float y1=0,y0=0;
//	return G_SqrtTable1[tk >> 24]<<m;
//	y0=G_SqrtTable1[sk]<<m/*(12-m)*/;
//	return y0;

/*	y1=y0/2+(xk>>1)/y0;
	y0=y1/2+(xk>>1)/y1;
	y1=y0/2+(xk>>1)/y0;
	return y1;

	while(1)
	{
		y1=y0/2+(xk>>1)/y0;
		if(fabs(y1-y0)<0.1)
			break;
		else 
			y0=y1;
	}
	return y1;*/
}//end

int _tmain(int argc, TCHAR* argv[], TCHAR* envp[])
{
	int i,j,k=100;;
	float sq;
	for (i=0;i<262144;i++)
	{
		G_SqrtTable[i] = sqrt(i);
		G_SqrtTable1[i] = int(G_SqrtTable[i]);
	}
	printf("%d\n",sizeof(float));
	goto l1;
	unsigned long shu;
	printf("请输入一个正数:");
	scanf("%ld",&shu);
	if(shu<=0)
		 printf("输入错误！");
	else
		 printf("%d\t%f\n",SquareRoot(shu),sqrt(shu));

	return 0;
	

l1:	DWORD t1,t2;
	t1=GetTickCount();
for( j=1;j<100000;j++ )
	for (i=69;i<79;i++)
	{
		sq = sqrt(i);
	}
	t2=GetTickCount();
	printf("lib sqrt:\t%d\n",t2-t1);
	
	t1=GetTickCount();
//for( j=1;j<10;j++ )
	unsigned long ui;
	unsigned long usq;
for(j=0;j<100000;j++)
	for (ui=69;ui<79;ui++)
	{
		//k=100/10;
		//sq = G_SqrtTable[i];//sqrt2(i);
		usq = SquareRoot(ui);
		
	}
	t2=GetTickCount();
	printf("my sqrt:\t%d\n",t2-t1);

	return 0;
}