added comments in snli/train.py, no code changes (pytorch#177)

snli/train.py

@@ -38,6 +38,8 @@
 config.n_embed = len(inputs.vocab)
 config.d_out = len(answers.vocab)
 config.n_cells = config.n_layers
+
+# double the number of cells for bidirectional networks
 if config.birnn:
     config.n_cells *= 2
 
@@ -66,41 +68,71 @@
     train_iter.init_epoch()
     n_correct, n_total = 0, 0
     for batch_idx, batch in enumerate(train_iter):
+
+        # switch model to training mode, clear gradient accumulators
         model.train(); opt.zero_grad()
+
         iterations += 1
+
+        # forward pass
         answer = model(batch)
+
+        # calculate accuracy of predictions in the current batch
         n_correct += (torch.max(answer, 1)[1].view(batch.label.size()).data == batch.label.data).sum()
         n_total += batch.batch_size
         train_acc = 100. * n_correct/n_total
+
+        # calculate loss of the network output with respect to training labels
         loss = criterion(answer, batch.label)
+
+        # backpropagate and update optimizer learning rate
         loss.backward(); opt.step()
+
+        # checkpoint model periodically
         if iterations % args.save_every == 0:
             snapshot_prefix = os.path.join(args.save_path, 'snapshot')
             snapshot_path = snapshot_prefix + '_acc_{:.4f}_loss_{:.6f}_iter_{}_model.pt'.format(train_acc, loss.data[0], iterations)
             torch.save(model, snapshot_path)
             for f in glob.glob(snapshot_prefix + '*'):
                 if f != snapshot_path:
                     os.remove(f)
+
+        # evaluate performance on validation set periodically
         if iterations % args.dev_every == 0:
+
+            # switch model to evaluation mode
             model.eval(); dev_iter.init_epoch()
+
+            # calculate accuracy on validation set
             n_dev_correct, dev_loss = 0, 0
             for dev_batch_idx, dev_batch in enumerate(dev_iter):
                  answer = model(dev_batch)
                  n_dev_correct += (torch.max(answer, 1)[1].view(dev_batch.label.size()).data == dev_batch.label.data).sum()
                  dev_loss = criterion(answer, dev_batch.label)
             dev_acc = 100. * n_dev_correct / len(dev)
+
             print(dev_log_template.format(time.time()-start,
                 epoch, iterations, 1+batch_idx, len(train_iter),
                 100. * (1+batch_idx) / len(train_iter), loss.data[0], dev_loss.data[0], train_acc, dev_acc))
+
+            # update best valiation set accuracy
             if dev_acc > best_dev_acc:
+
+                # found a model with better validation set accuracy
+
                 best_dev_acc = dev_acc
                 snapshot_prefix = os.path.join(args.save_path, 'best_snapshot')
                 snapshot_path = snapshot_prefix + '_devacc_{}_devloss_{}__iter_{}_model.pt'.format(dev_acc, dev_loss.data[0], iterations)
+
+                # save model, delete previous 'best_snapshot' files
                 torch.save(model, snapshot_path)
                 for f in glob.glob(snapshot_prefix + '*'):
                     if f != snapshot_path:
                         os.remove(f)
+
         elif iterations % args.log_every == 0:
+
+            # print progress message
             print(log_template.format(time.time()-start,
                 epoch, iterations, 1+batch_idx, len(train_iter),
                 100. * (1+batch_idx) / len(train_iter), loss.data[0], ' '*8, n_correct/n_total*100, ' '*12))