数值计算-残差

public class aa {

public static void main(String[] args) {
double [][] a={{21.0,67.0,88.0,73.0},
{76.0,63.0,7.0,20.0},
{0.0,85.0,56.0,54.0},
{19.3,43.0,30.2,29.4}};
double [] b={141.0,109.0,218.0,93.7};
double[][] tem={{1,0,0,0},{0,1,0,0},{0,0,1,0},{0,0,0,1}};
double[][] m=new double[4][4];
double[] x=new double[4];
double[][] aa = new double[4][4];
double[] bb = new double[4];
//double[][] aa = a ;
for(int i=0;i<4;i++)
for(int j=0;j<4;j++)
aa[i][j] = a[i][j];
//double[] bb = b;
for(int i=0;i<4;i++)
bb[i] = b[i];
for(int k=0;k<3;k++){
if(a[k][k]==0)
break;
for(int i=k+1;i<4;i++)
{
m[i][k]=a[i][k]/a[k][k];
tem[i][k]=-m[i][k];
}

b=cheng(tem,b);