,-----.            
                                |start|            
                                |-----|            
                                `-----'            
                                   |               
                                   |               
                         ,-------------------.     
                         |Evaluate loss index|     
                         |-------------------|     
                         `-------------------'     
                                                   
,-------------------------------------------.      
|Improve neural network parameters          |      
|-------------------------------------------|  ,-. 
|* Calculate quasi-Newton training direction|  | | 
|* Calculate training rate                  |--|-| 
|                                           |  `-' 
`-------------------------------------------'    | 
                                                 | 
                                                   
                                              ,---.
                                              |end|
                                              |---|
                                              `---'