Better support for multiclass

Former-commit-id: 76bebf5f241f579fda7048f5e4a87ee9d49aa423

eval.py

@@ -1,4 +1,5 @@
 import torch
+import torch.nn.functional as F
 from tqdm import tqdm
 
 from dice_loss import dice_coeff
@@ -22,5 +23,9 @@ def eval_net(net, dataset, device, n_val):
         mask_pred = net(img).squeeze(dim=0)
 
         mask_pred = (mask_pred > 0.5).float()
-        tot += dice_coeff(mask_pred, true_mask.squeeze(dim=1)).item()
+        if net.n_classes > 1:
+            tot += F.cross_entropy(mask_pred.unsqueeze(dim=0), true_mask.unsqueeze(dim=0)).item()
+        else:
+            tot += dice_coeff(mask_pred, true_mask.squeeze(dim=1)).item()
+
     return tot / n_val

train.py

@@ -44,7 +44,10 @@ def train_net(net,
     n_train = len(iddataset['train'])
     n_val = len(iddataset['val'])
     optimizer = optim.Adam(net.parameters(), lr=lr)
-    criterion = nn.BCELoss()
+    if net.n_classes > 1:
+        criterion = nn.CrossEntropyLoss()
+    else:
+        criterion = nn.BCEWithLogitsLoss()
 
     for epoch in range(epochs):
         net.train()
@@ -87,8 +90,12 @@ def train_net(net,
                        dir_checkpoint + f'CP_epoch{epoch + 1}.pth')
             logging.info(f'Checkpoint {epoch + 1} saved !')
 
-        val_dice = eval_net(net, val, device, n_val)
-        logging.info('Validation Dice Coeff: {}'.format(val_dice))
+        val_score = eval_net(net, val, device, n_val)
+        if net.n_classes > 1:
+            logging.info('Validation cross entropy: {}'.format(val_score))
+
+        else:
+            logging.info('Validation Dice Coeff: {}'.format(val_score))
 
 
 def get_args():

unet/unet_model.py

@@ -33,7 +33,9 @@ class UNet(nn.Module):
         x = self.up2(x, x3)
         x = self.up3(x, x2)
         x = self.up4(x, x1)
-        x = self.outc(x)
+        logits = self.outc(x)
+        return logits
+
         if self.n_classes > 1:
             return F.softmax(x, dim=1)
         else: