autocorrelation.cpp

主要实现卷积功能

#include <stdio.h>
#include <math.h>

 

void kkfft(double pr[],double pi[],int n,int k,double fr[],double fi[],int l, int il)//快速傅立叶变换
 
  { int it,m,is,i,j,nv,l0;
    double p,q,s,vr,vi,poddr,poddi;
    for (it=0; it<=n-1; it++)
      { m=it; is=0;
        for (i=0; i<=k-1; i++)
          { j=m/2; is=2*is+(m-2*j); m=j;}
        fr[it]=pr[is]; fi[it]=pi[is];
      }
    pr[0]=1.0; pi[0]=0.0;
    p=6.283185306/(1.0*n);
    pr[1]=cos(p); pi[1]=-sin(p);
    if (l!=0) pi[1]=-pi[1];
    for (i=2; i<=n-1; i++)
      { p=pr[i-1]*pr[1]; q=pi[i-1]*pi[1];
        s=(pr[i-1]+pi[i-1])*(pr[1]+pi[1]);
        pr[i]=p-q; pi[i]=s-p-q;
      }
    for (it=0; it<=n-2; it=it+2)
      { vr=fr[it]; vi=fi[it];
        fr[it]=vr+fr[it+1]; fi[it]=vi+fi[it+1];
        fr[it+1]=vr-fr[it+1]; fi[it+1]=vi-fi[it+1];
      }
    m=n/2; nv=2;
    for (l0=k-2; l0>=0; l0--)
      { m=m/2; nv=2*nv;
        for (it=0; it<=(m-1)*nv; it=it+nv)
          for (j=0; j<=(nv/2)-1; j++)
            { p=pr[m*j]*fr[it+j+nv/2];
              q=pi[m*j]*fi[it+j+nv/2];
              s=pr[m*j]+pi[m*j];
              s=s*(fr[it+j+nv/2]+fi[it+j+nv/2]);
              poddr=p-q; poddi=s-p-q;
              fr[it+j+nv/2]=fr[it+j]-poddr;
              fi[it+j+nv/2]=fi[it+j]-poddi;
              fr[it+j]=fr[it+j]+poddr;
              fi[it+j]=fi[it+j]+poddi;
            }
      }
    if (l!=0)
      for (i=0; i<=n-1; i++)
        { fr[i]=fr[i]/(1.0*n);
          fi[i]=fi[i]/(1.0*n);
        }
    if (il!=0)
      for (i=0; i<=n-1; i++)
        { pr[i]=sqrt(fr[i]*fr[i]+fi[i]*fi[i]);
          if (fabs(fr[i])<0.000001*fabs(fi[i]))
            { if ((fi[i]*fr[i])>0) pi[i]=90.0;
              else pi[i]=-90.0;
            }
          else
            pi[i]=atan(fi[i]/fr[i])*360.0/6.283185306;
        }
    return;
  }


void bcmul(double ar[],double ai[],double br[],double bi[],int m, double cr[],double ci[]) //矩阵相乘
 

  { int i;
    double p,q,s;
    for (i=0; i<=m-1; i++)
    {
        cr[i]=0.0; ci[i]=0.0;
        
        p=ar[i]*br[i];
        q=ai[i]*bi[i];
        s=(ar[i]+ai[i])*(br[i]+bi[i]);
        cr[i]=cr[i]+p-q;
        ci[i]=ci[i]+s-p-q;
     }
      
    return;
  }

void taxis(double a[],double b[],int m)//对数组a进行排序，后把值放在数组b中
{
	int i;
	for (i=0;i<m/2;i++)
	{
		b[i] = a[m/2+i];
		b[m/2+i] = a[i];
	}
}

int maxmam(double a[], int m)//找最大值并返回所对应的横坐标的值
{
    double max;
	int i;
	int k=0;
	max = a[0];
	for(i=1;i<m;i++)
	{
		if(a[i]>=max)
		{
			max =a[i];
			k=i;
		}
	}
	k = k+1-m/2;
	return k;
        
}



void main(){             //求a与b的相关系数c
FILE *fpc;
fpc=fopen("F:\\c.txt", "w");

FILE *fpa,*fpb;
fpa=fopen("F:\\a.txt", "r");
fpb=fopen("F:\\b.txt", "r");

int n;

double pr[128],pi[128],fr[128],fi[128];
double ar[128],ai[128],br[128],bi[128],cr[128],ci[128];

   for (int k=0; !feof(fpa); k++) //赋值
	{

	   fscanf(fpa,"%lf",&pr[k]);
	   pi[k] = 0.0;
   }
    fclose(fpa);

	kkfft(pr,pi,128,7,ar,ai,0,0); //a的傅立叶变换

    for ( k=0; !feof(fpb); k++) //赋值
	{

	   fscanf(fpb,"%lf",&pr[k]);
	   pi[k] = 0.0;
    }
    fclose(fpb);
    kkfft(pr,pi,128,7,br,bi,0,0); //b的傅立叶变换

	for(k=0;k<128;k++)
	{
		bi[k]=-bi[k];
	}
	bcmul(ar,ai,br,bi,128,cr,ci);//矩阵相乘

    kkfft(cr,ci,128,7,fr,fi,1,1); //逆傅立叶变换

    taxis(cr,ci,128);//重新排序

    n= maxmam(ci,128);
    
    fprintf(fpc,"%d \n", n);
	
	fclose(fpc);
/*	for(int i=0; i<512; i++)
	{
         fprintf(fpc,"%e \n", cr[i]);
	}
	fclose(fpc);*/
 
}