c语言使用分解法求解对称联立线性方程式.txt

利用C语言通过分解法求解对称联立线性方程式

#include <math.h>
  #include <stdio.h>
/*
使用分解法求解对称联立线性方程式
*/
  int ldle(double *a,int n,int m,double *c)
  //int n,m;
  //double a[],c[];
  { int i,j,l,k,u,v,w,k1,k2,k3;
    double p;
    if (fabs(a[0])+1.0==1.0)
      { printf("fail\n"); return(-2);}
    for (i=1; i<=n-1; i++)
      { u=i*n; a=a/a[0];}
    for (i=1; i<=n-2; i++)
      { u=i*n+i;
        for (j=1; j<=i; j++)
          { v=i*n+j-1; l=(j-1)*n+j-1;
            a=a-a[v]*a[v]*a[l];
          }
        p=a;
        if (fabs(p)+1.0==1.0)
          { printf("fail\n"); return(-2);}
        for (k=i+1; k<=n-1; k++)
          { u=k*n+i;
            for (j=1; j<=i; j++)
              { v=k*n+j-1; l=i*n+j-1; w=(j-1)*n+j-1;
  a=a-a[v]*a[l]*a[w];
              }
            a=a/p;
          }
      }
    u=n*n-1;
    for (j=1; j<=n-1; j++)
      { v=(n-1)*n+j-1; w=(j-1)*n+j-1;
        a=a-a[v]*a[v]*a[w];
      }
    p=a;
    if (fabs(p)+1.0==1.0)
      { printf("fail\n"); return(-2);}
    for (j=0; j<=m-1; j++)
    for (i=1; i<=n-1; i++)
      { u=i*m+j;
        for (k=1; k<=i; k++)
          { v=i*n+k-1; w=(k-1)*m+j;
            c=c-a[v]*c[w];
          }
      }
    for (i=1; i<=n-1; i++)
      { u=(i-1)*n+i-1;
        for (j=i; j<=n-1; j++)
          { v=(i-1)*n+j; w=j*n+i-1;
            a[v]=a*a[w];
          }
      }
    for (j=0; j<=m-1; j++)
      { u=(n-1)*m+j;
        c=c/p;
        for (k=1; k<=n-1; k++)
          { k1=n-k; k3=k1-1; u=k3*m+j;
            for (k2=k1; k2<=n-1; k2++)
              { v=k3*n+k2; w=k2*m+j;
                c=c-a[v]*c[w];
              }
            c=c/a[k3*n+k3];
          }
      }
    return(2);
  }
  main()
  { int i;
    static double a[5][5]={ {5.0,7.0,6.0,5.0,1.0},
           {7.0,10.0,8.0,7.0,2.0},{6.0,8.0,10.0,9.0,3.0},
           {5.0,7.0,9.0,10.0,4.0},{1.0,2.0,3.0,4.0,5.0}};
    static double c[5][2]={ {24.0,96.0},{34.0,136.0},
           {36.0,144.0},{35.0,140.0},{15.0,60.0}};
double *pa,*pc;
pa=(double *)a;
pc=(double *)c;
    if (ldle(pa,5,2,pc)>0)
      for (i=0; i<=4; i++)
        printf("x(%d)=%13.7e,   %13.7e\n",i,c[0],c[1]);
  }