softmax 函数

总结为:   将一组数变换为  总和为1,各个数为0~1之间的软性归一化结果。 

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关于logistic regression中的softmax 函数

是用来柔化输出值,减小值之间的差。

用来归一化一组值到0~1之间,  总和为1. 

步骤为: 

  1. 求出最大值max
  2. 由exp表达式将各个值转化为0~1之间的数  x[i] =  exp(x[i] - max)
  3. 求sum,归一化。 
  1. void LogisticRegression::softmax(double *x) {                                     
  2.                                                            
  3.   double max = 0.0;                                                                
  4.   double sum = 0.0;                                                                
  5.                                                                                    
  6.   for(int i=0; i<n_out; i++) if(max < x[i]) max = x[i];                            
  7.   for(int i=0; i<n_out; i++) {                                                     
  8.     x[i] = exp(x[i] - max);                                                        
  9.     sum += x[i];                                                                   
  10.   }                                                                                
  11.                                                                                    
  12.   for(int i=0; i<n_out; i++) x[i] /= sum;    
  13. }                       

 

原文地址:https://www.cnblogs.com/anyview/p/5019187.html