reversebits.cpp

快速fft反转位程序

#include<stdio.h>
#include<iostream.h>
#include<math.h>
#define NumSample 4096
#define M 12
#define Pi 3.14159265358979
unsigned int ReverseBits(unsigned int index,unsigned int P)
{
    unsigned int i,Rev=0;
		for(i=0; i<P; i++)
	{
		if(index%2==1)
		Rev+=(int)pow(2,P-1-i);
		else
			Rev=Rev;
		index=index>> 1;
	}
	return Rev;
}
/*void FFT(float Realin[NumSample],float Imagein[NumSample])
{
	float AngleNumerato=-2*Pi;
	float *pReal,*pImage;
	unsigned int i,j,k,n,BlockSize,BlockEnd;
	float Temp,DeltaAngle,DeltaAr,Alpha,Beta,TR,Ti,AR,AI;
	pReal=new float(NumSample);
	pImage=new float(NumSample);
	for(i=0;i<NumSample;i++)
	{
		j=(ReverseBits(i,M);//排序
	    pReal[j]=Realin[i];
		pImage[j]=Imagein[i];
	}
	for(i=0;i<Numsample;i++)
	{
		Realin[i]=pReal[i];
		Imagein[i]=pImage[i];
	}
    delete [NumSample]pReal;
	delete [NumSample]pImage;
	BlockEnd=1;
	BlockSize=2;
	while(BlockSize<=NumSample)
	{
		DeltaAngle=AngleNumerator/BlockSize;
		Alpha=sin(0.5*DeltaAngle);
		Alpha=2*Alpha*Alpha;
		Beta=Sin(DeltaAngle);
		i=0;
    while(i<NumSample)
	{
		AR=1;
		AI=0;
		j=i;
		for(n=0;n<BlockEnd;n++)
		{
			k=j+BlockEnd;
			TR=AR*Realin[k]-AI*Imagein[k];
			TI=AI*realin[k]+AR*Imagein[k];
			Realin[k]=Realin[j]-TR;
			Imagein[k]=Imagein[j]-TI;
			Realin[j]=Realin[j]+TR;
			Imagein[j]=Imagein[j]+TI;
			DeltaAr=Alpha*AR+Beta*AI;
			AI=AI-(Alpha*AI-Beta*AR);
			AR=AR-DeltaAr;
			j++;
		}
		i+=BlockSize;
	}
	BlockEnd=BlockSize;
	BlockSize=BlockSize*2;
	}

*/



void main()
{
	unsigned int n,m;
	n=152;
	m=ReverseBits(n,M);
	cout<<"m="<<m<<endl;
}