Add pos_weight and support for summing over classes to BCE impl in train scripts

timm/loss/binary_cross_entropy.py

@@ -2,7 +2,7 @@
 
 Hacked together by / Copyright 2021 Ross Wightman
 """
-from typing import Optional
+from typing import Optional, Union
 
 import torch
 import torch.nn as nn
@@ -14,18 +14,30 @@ class BinaryCrossEntropy(nn.Module):
     NOTE for experiments comparing CE to BCE /w label smoothing, may remove
     """
     def __init__(
-            self, smoothing=0.1, target_threshold: Optional[float] = None, weight: Optional[torch.Tensor] = None,
-            reduction: str = 'mean', pos_weight: Optional[torch.Tensor] = None):
+            self,
+            smoothing=0.1,
+            target_threshold: Optional[float] = None,
+            weight: Optional[torch.Tensor] = None,
+            reduction: str = 'mean',
+            sum_classes: bool = False,
+            pos_weight: Optional[Union[torch.Tensor, float]] = None,
+    ):
         super(BinaryCrossEntropy, self).__init__()
         assert 0. <= smoothing < 1.0
+        if pos_weight is not None:
+            if not isinstance(pos_weight, torch.Tensor):
+                pos_weight = torch.tensor(pos_weight)
         self.smoothing = smoothing
         self.target_threshold = target_threshold
-        self.reduction = reduction
+        self.reduction = 'none' if sum_classes else reduction
+        self.sum_classes = sum_classes
         self.register_buffer('weight', weight)
         self.register_buffer('pos_weight', pos_weight)
 
     def forward(self, x: torch.Tensor, target: torch.Tensor) -> torch.Tensor:
-        assert x.shape[0] == target.shape[0]
+        batch_size = x.shape[0]
+        assert batch_size == target.shape[0]
+
         if target.shape != x.shape:
             # NOTE currently assume smoothing or other label softening is applied upstream if targets are already sparse
             num_classes = x.shape[-1]
@@ -34,14 +46,20 @@ class BinaryCrossEntropy(nn.Module):
             on_value = 1. - self.smoothing + off_value
             target = target.long().view(-1, 1)
             target = torch.full(
-                (target.size()[0], num_classes),
+                (batch_size, num_classes),
                 off_value,
                 device=x.device, dtype=x.dtype).scatter_(1, target, on_value)
+
         if self.target_threshold is not None:
             # Make target 0, or 1 if threshold set
             target = target.gt(self.target_threshold).to(dtype=target.dtype)
-        return F.binary_cross_entropy_with_logits(
+
+        loss = F.binary_cross_entropy_with_logits(
             x, target,
             self.weight,
             pos_weight=self.pos_weight,
-            reduction=self.reduction)
+            reduction=self.reduction,
+        )
+        if self.sum_classes:
+            loss = loss.sum(-1).mean()
+        return loss

train.py

@@ -255,8 +255,12 @@ group.add_argument('--jsd-loss', action='store_true', default=False,
                    help='Enable Jensen-Shannon Divergence + CE loss. Use with `--aug-splits`.')
 group.add_argument('--bce-loss', action='store_true', default=False,
                    help='Enable BCE loss w/ Mixup/CutMix use.')
+group.add_argument('--bce-sum', action='store_true', default=False,
+                   help='Sum over classes when using BCE loss.')
 group.add_argument('--bce-target-thresh', type=float, default=None,
-                   help='Threshold for binarizing softened BCE targets (default: None, disabled)')
+                   help='Threshold for binarizing softened BCE targets (default: None, disabled).')
+group.add_argument('--bce-pos-weight', type=float, default=None,
+                   help='Positive weighting for BCE loss.')
 group.add_argument('--reprob', type=float, default=0., metavar='PCT',
                    help='Random erase prob (default: 0.)')
 group.add_argument('--remode', type=str, default='pixel',
@@ -699,12 +703,21 @@ def main():
     elif mixup_active:
         # smoothing is handled with mixup target transform which outputs sparse, soft targets
         if args.bce_loss:
-            train_loss_fn = BinaryCrossEntropy(target_threshold=args.bce_target_thresh)
+            train_loss_fn = BinaryCrossEntropy(
+                target_threshold=args.bce_target_thresh,
+                sum_classes=args.bce_sum,
+                pos_weight=args.bce_pos_weight,
+            )
         else:
             train_loss_fn = SoftTargetCrossEntropy()
     elif args.smoothing:
         if args.bce_loss:
-            train_loss_fn = BinaryCrossEntropy(smoothing=args.smoothing, target_threshold=args.bce_target_thresh)
+            train_loss_fn = BinaryCrossEntropy(
+                smoothing=args.smoothing,
+                target_threshold=args.bce_target_thresh,
+                sum_classes=args.bce_sum,
+                pos_weight=args.bce_pos_weight,
+            )
         else:
             train_loss_fn = LabelSmoothingCrossEntropy(smoothing=args.smoothing)
     else: