computer vision - SURF comparison code giving issues -

i doing surf comparison identify objects in images calculating euclidean distances between desriptors. following code isnt working. ipoint surf feature point, apreciated.

 list<ipoint> ipts = new list<ipoint>(); dictionary<string, list<ipoint>> objs = new dictionary<string, list<ipoint>>(); double distance(ipoint a, ipoint b) {     double dis = 0;     (int = 0; < 64; i++)     {          dis += math.sqrt(math.pow((a.descriptor[i] - b.descriptor[i]), 2));     }     return (dis); } bool matchpoint(ipoint a, list<ipoint> l, out string e) {     e = "";     double smallest = double.maxvalue;     string s = string.empty;     (int = 0; < l.count; i++)     {         var d = distance(a, l[i]);         if (d < smallest)         {             smallest = d;             s = i.tostring();         }     }     if (smallest < 0.5)     {         e = s;         return true;     }     else     {         return false;// null;     }     return false; } string match(out double per) {     string h;     dictionary<string, double> torn = new dictionary<string, double>();     foreach (string s in objs.keys.tolist())     {         int count = 0;         (int = 0; < objs[s].count; i++)         {             if (matchpoint(objs[s][i], ipts,out h))             {                 count++;             }         }         torn[s] = count / objs[s].count;         count = 0;     }     string smalln = "";     double smallest = double.maxvalue;     foreach (string s in torn.keys.tolist())     {         if (torn[s] < smallest)         {             smallest = torn[s];             smalln = s;         }     }     per = smallest;     return smalln; } private void button1_click(object sender, eventargs e) {     double d;     match(out d);     messagebox.show(match(out d) + " " + d.tostring()); } 

should be:

double distance(ipoint a, ipoint b) {     double dis = 0;     (int = 0; < 64; i++)     {          dis += math.pow((a.descriptor[i] - b.descriptor[i]), 2);     }     return math.sqrt(dis); } 

you squaring , taking root of each difference, doing absolute value. try remember simple example of pythagoras: c=sqrt(a*a+b*b) , not c=sqrt(a*a)+sqrt(b*b)