use dim() to simplify gc

thanks @nestordemeure for pointing out code simplification

Author: lessw2020

ranger/ranger.py

@@ -130,17 +130,12 @@ def step(self, closure=None):
                 #begin computations 
                 exp_avg, exp_avg_sq = state['exp_avg'], state['exp_avg_sq']
                 beta1, beta2 = group['betas']
-
-                
-
-                #gc work  #3 = conv only, 1 = conv +fc
-                if len(list(grad.size()))>self.gc_gradient_threshold:                    
-                   grad.add_(-grad.mean(dim = tuple(range(1,len(list(grad.size())))), keepdim = True))
+              
 
-                #GC operation for Conv layers and FC layers   
-                if len(list(grad.size()))>self.gc_gradient_threshold:
-                   grad.add_(-grad.mean(dim = tuple(range(1,len(list(grad.size())))), keepdim = True))
-
+                #GC operation for Conv layers and FC layers       
+                if grad.dim() > self.gc_gradient_threshold:                    
+                   grad.add_(-grad.mean(dim = tuple(range(1,grad.dim())), keepdim = True))
+                           
 
 
                 state['step'] += 1