Question

-(IBAction) balancer: (id) sender{
 double M[4][4];
 M[0][0] = 6.0;
 M[0][1] = 0.0;
 M[0][2] = -1.0;
 M[0][3] = 0.0;
 M[1][0] = 12.0;
 M[1][1] = 0.0;
 M[1][2] = 0.0;
 M[1][3] = 2.0;
 M[2][0] = 6.0;
 M[2][1] = 2.0;
 M[2][2] = -2.0;
 M[2][3] = 1.0;
 M[3][0] = 0.0;
 M[3][1] = 0.0;
 M[3][2] = 0.0;
 M[3][3] = 0.0;
 int rowCount = 4;


 int columnCount = 4;

 int lead = 0;
 for (int r = 0; r < rowCount; r++) {
  if (lead >= columnCount)
   break;

  int i = r;
  while (M[i][lead] == 0) {
   i++;
   if (i == rowCount) {
    i = r;
    lead++;
    if (lead == columnCount){


     break;
    }
   }
  }
  double temp[4] ;
  temp[0] = M[r][0];
  temp[1] = M[r][1];
  temp[2] = M[r][2];
  temp[3] = M[r][3];
  M[r][0] = M[i][0];
  M[r][1] = M[i][1];
  M[r][2] = M[i][2];
  M[r][3] = M[i][3];
  M[i][0] = temp[0];
  M[i][1] = temp[1];
  M[i][2] = temp[2];
  M[i][3] = temp[3];

  double lv = M[r][lead];
  for (int j = 0; j < columnCount; j++)
   M[r][j] = M[r][j] / lv;


  for (int f = 0; f < rowCount; f++) {
   if (f != r) {
    double l = M[f][lead];
    for (int j = 0; j < columnCount; j++)
     M[f][j] =  M[f][j] - l * M[r][j];
   }
  }
  lead++;

    }
 NSString* myNewString = [NSString stringWithFormat:@"%g",M[0][3]]; 

 label1.text = myNewString;

}

这是返回NaN，而它应该为M [0] [3]返回.16666667。对于如何解决这个问题，有任何的建议吗？

Answer 1

您正在进行除法以获取M[r][j]的值，您应该在执行除法之前检查lv ! = 0.0。

double TOLERANCE = 1.0E-10;
if (fabs(lv) < TOLERANCE){
      NSLog(@"Division over ZERO");
      exit(1);
}

[edit]假设你的逻辑是正确的。

Objective-C（iPhone SDK） - 化学方程平衡器代码帮助

1 个答案: