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Task: cv-classification-loss

CV Classification Loss Function Design

Research Question

Design a novel classification loss function for deep convolutional neural networks that improves test accuracy across different architectures and datasets.

Background

The cross-entropy loss is the standard training objective for classification networks, but it has known limitations: it treats all misclassifications equally, assigns high confidence to correct predictions without margin, and does not adapt to training dynamics. Researchers have proposed alternatives:

  • Label Smoothing (Szegedy et al., 2016): Softens hard targets to prevent overconfidence, CE with targets = (1-eps)*one_hot + eps/C
  • Focal Loss (Lin et al., ICCV 2017): Down-weights easy examples via (1-pt)^gamma modulation
  • PolyLoss (Leng et al., ICLR 2022): Extends CE with polynomial correction terms, CE + eps*(1-pt)

However, these methods are either static or address only specific failure modes. There is room to design loss functions that combine multiple insights: confidence calibration, curriculum-style epoch adaptation, class-count awareness, or learned temperature scaling.

What You Can Modify

The compute_loss(logits, targets, config) function (lines 165-185) in custom_loss.py. This function receives raw logits, integer targets, and a config dict, and must return a differentiable scalar loss.

You can modify:

  • The loss formulation (cross-entropy variants, margin losses, etc.)
  • Confidence-based reweighting schemes
  • Epoch-dependent curriculum strategies using config['epoch'] and config['total_epochs']
  • Class-count-dependent behavior using config['num_classes']
  • Temperature or logit scaling
  • Auxiliary regularization terms (entropy, logit penalties, etc.)

The config dict provides: num_classes (int), epoch (int, 0-indexed), total_epochs (int).

Important: The evaluation loss (for test_loss reporting) always uses standard cross-entropy. Your loss function only affects training.

Evaluation

  • Metric: Best test accuracy (%, higher is better)
  • Architectures & datasets:
    • ResNet-56 on CIFAR-100 (deep residual, 100 classes)
    • VGG-16-BN on CIFAR-100 (deep non-residual with BatchNorm, 100 classes)
    • MobileNetV2 on FashionMNIST (lightweight inverted-residual, 10 classes) — hidden, evaluated on final submission only
  • Training: SGD (lr=0.1, momentum=0.9, wd=5e-4), cosine annealing, 200 epochs
  • Data augmentation: RandomCrop(32, pad=4) + RandomHorizontalFlip

pytorch-vision/custom_loss.py [EDITABLE — lines 246–266 only]

     1: """CV Classification Loss Benchmark.
     2: 
     3: Train vision models (ResNet, VGG, MobileNetV2) on CIFAR-10/100/FashionMNIST to evaluate
     4: classification loss function designs.
     5: 
     6: FIXED: Model architectures, weight initialization, data pipeline, training loop.
     7: EDITABLE: compute_loss() function.
     8: 
     9: Usage:
    10:     python custom_loss.py
AssistantStep 1edit
Tool Input
1{
2  "op": "replace",
3  "filename": "pytorch-vision/custom_loss.py",
4  "start_line": 246,
5  "end_line": 266,
6  "content": "def compute_loss(logits, targets, config):\n    \"\"\"Adaptive Curriculum Margin Loss (ACML).\n\n    Combines:\n    1. Curriculum margin that increases with epoch progression.\n    2. Focal weighting for hard examples.\n    3. Label smoothing for calibration.\n    4. Adaptive temperature scaling.\n\n    Hyperparameters:\n        base_margin: maximum margin at final epoch\n        gamma: controls margin progression rate\n        beta: focal weighting strength\n        tau: temperature scaling magnitude\n        smoothing_eps: label smoothing factor\n    \"\"\"\n    # Hyperparameters (hardcoded)\n    base_margin = 0.5\n    gamma = 2.0\n    beta = 2.0\n    tau = 1.0\n    smoothing_eps = 0.1\n\n    num_classes = config['num_classes']\n    epoch = config['epoch']\n    total_epochs = config['total_epochs']\n\n    B = logits.size(0)\n\n    # Curriculum progression factor (0 to 1)\n    progress = epoch / max(total_epochs - 1, 1)  # avoid division by zero\n\n    # Dynamic margin that increases with progress\n    margin = base_margin * (progress ** gamma)\n\n    # Adaptive temperature: starts warm (higher temp), ends cool (lower temp)\n    temperature = 1.0 + tau * (1.0 - progress)  # temperature decreases as progress increases\n\n    # Apply margin to logits: subtract margin from true class logit\n    logits_adjusted = logits.clone()\n    logits_adjusted[range(B), targets] -= margin\n\n    # Apply temperature scaling\n    logits_adjusted = logits_adjusted / temperature\n\n    # Compute softmax probabilities\n    probs = F.softmax(logits_adjusted, dim=-1)\n    pt = probs[range(B), targets]  # probability of true class\n\n    # Focal weighting: down-weight easy examples\n    focal_weight = (1.0 - pt) ** beta\n\n    # Label smoothing target distribution\n    one_hot = F.one_hot(targets, num_classes).float()\n    smoothed_targets = (1.0 - smoothing_eps) * one_hot + smoothing_eps / num_classes\n\n    # Compute cross-entropy between smoothed targets and adjusted logits\n    log_probs = F.log_softmax(logits_adjusted, dim=-1)\n    ce = -(smoothed_targets * log_probs).sum(dim=-1)  # [B]\n\n    # Weighted loss\n    loss = (focal_weight * ce).mean()\n\n    return loss"
7}
Tool ResultStep 1
OK: Replaced lines 246..266 with 64 line(s) in pytorch-vision/custom_loss.py. Editable range: 246–309.

[Current file: pytorch-vision/custom_loss.py | editable: 246–309 | total: 479 lines]
   243| # ============================================================================
   244| 
   245| # -- EDITABLE REGION START (lines 246-266) ------------------------------------
   246  def compute_loss(logits, targets, config):
   247      """Adaptive Curriculum Margin Loss (ACML).
   248  
   249      Combines:
   250      1. Curriculum margin that increases with epoch progression.
   251      2. Focal weighting for hard examples.
   252      3. Label smoothing for calibration.
   253      4. Adaptive temperature scaling.
   254  
   255      Hyperparameters:
   256          base_margin: maximum margin at final epoch
   257          gamma: controls margin progression rate
   258          beta: focal weighting strength
   259          tau: temperature scaling magnitude
   260          smoothin
AssistantStep 2test
Tool ResultStep 2
[Test #1] (2 tests remaining; call submit(n=N) to choose which test result to submit as final)

### resnet56-cifar100 (scripts/resnet56_cifar100.sh)
Training progress (last epochs):
TRAIN_METRICS: epoch=160 train_loss=0.3967 train_acc=87.46 test_loss=1.3638 test_acc=67.49 lr=0.009549
TRAIN_METRICS: epoch=170 train_loss=0.2423 train_acc=92.55 test_loss=1.2600 test_acc=69.82 lr=0.005450
TRAIN_METRICS: epoch=180 train_loss=0.1203 train_acc=96.70 test_loss=1.1875 test_acc=72.03 lr=0.002447
TRAIN_METRICS: epoch=190 train_loss=0.0667 train_acc=98.40 test_loss=1.1575 test_acc=72.46 lr=0.000616
TRAIN_METRICS: epoch=200 train_loss=0.0538 train_acc=98.86 test_loss=1.1574 test_acc=72.65 lr=0.000000
Final metrics (resnet56-cifar100): test_acc_resnet56-cifar100=72.66

### vgg16bn-cifar100 (scripts/vgg16bn_cifar100.sh)
Training progress (last epochs):
TRAIN_METRICS: epoch=160 train_loss=0.1947 train_acc=93.73 test_loss=1.4635 test_acc=68.79 lr=0.009549
TRAIN_METRICS: epoch=170 train_loss=0.0744 trai
AssistantStep 3edit
Tool Input
1{
2  "op": "replace",
3  "filename": "pytorch-vision/custom_loss.py",
4  "start_line": 246,
5  "end_line": 309,
6  "content": "def compute_loss(logits, targets, config):\n    \"\"\"Adaptive Margin Focal Loss (AMFL).\n\n    Combines:\n    1. Sample-dependent margin: harder examples get larger margin.\n    2. Curriculum progression: margin magnitude increases over epochs.\n    3. Focal weighting for hard examples.\n    4. Label smoothing for calibration.\n    5. Adaptive temperature scaling.\n\n    Hyperparameters:\n        base_margin: maximum margin at final epoch for easy samples\n        gamma: controls margin progression rate over epochs\n        alpha: controls margin scaling with sample hardness\n        beta: focal weighting strength\n        tau: temperature scaling magnitude\n        smoothing_eps: label smoothing factor\n    \"\"\"\n    # Hyperparameters (hardcoded)\n    base_margin = 0.3\n    gamma = 1.0\n    alpha = 1.0\n    beta = 2.0\n    tau = 0.5\n    smoothing_eps = 0.1\n\n    num_classes = config['num_classes']\n    epoch = config['epoch']\n    total_epochs = config['total_epochs']\n\n    B = logits.size(0)\n\n    # Curriculum progression factor (0 to 1)\n    progress = epoch / max(total_epochs - 1, 1)  # avoid division by zero\n\n    # Adaptive temperature: starts warm (higher temp), ends cool (lower temp)\n    temperature = 1.0 + tau * (1.0 - progress)  # temperature decreases as progress increases\n\n    # Apply temperature scaling to raw logits\n    logits_scaled = logits / temperature\n\n    # Compute raw probabilities (before margin)\n    probs_raw = F.softmax(logits_scaled, dim=-1)\n    pt_raw = probs_raw[range(B), targets]  # probability of true class before margin\n\n    # Sample-dependent margin: larger margin for harder examples\n    hardness = 1.0 - pt_raw  # hardness ∈ [0,1]\n    margin = base_margin * (progress ** gamma) * (hardness ** alpha)  # [B]\n\n    # Apply margin to logits: subtract margin from true class logit\n    logits_adjusted = logits_scaled.clone()\n    logits_adjusted[range(B), targets] -= margin\n\n    # Compute probabilities after margin\n    probs = F.softmax(logits_adjusted, dim=-1)\n    pt = probs[range(B), targets]  # probability of true class after margin\n\n    # Focal weighting: down-weight easy examples\n    focal_weight = (1.0 - pt) ** beta\n\n    # Label smoothing target distribution\n    one_hot = F.one_hot(targets, num_classes).float()\n    smoothed_targets = (1.0 - smoothing_eps) * one_hot + smoothing_eps / num_classes\n\n    # Compute cross-entropy between smoothed targets and adjusted logits\n    log_probs = F.log_softmax(logits_adjusted, dim=-1)\n    ce = -(smoothed_targets * log_probs).sum(dim=-1)  # [B]\n\n    # Weighted loss\n    loss = (focal_weight * ce).mean()\n\n    return loss"
7}
Tool ResultStep 3
OK: Replaced lines 246..309 with 72 line(s) in pytorch-vision/custom_loss.py. Editable range: 246–317.

[Current file: pytorch-vision/custom_loss.py | editable: 246–317 | total: 487 lines]
   243| # ============================================================================
   244| 
   245| # -- EDITABLE REGION START (lines 246-266) ------------------------------------
   246  def compute_loss(logits, targets, config):
   247      """Adaptive Margin Focal Loss (AMFL).
   248  
   249      Combines:
   250      1. Sample-dependent margin: harder examples get larger margin.
   251      2. Curriculum progression: margin magnitude increases over epochs.
   252      3. Focal weighting for hard examples.
   253      4. Label smoothing for calibration.
   254      5. Adaptive temperature scaling.
   255  
   256      Hyperparameters:
   257          base_margin: maximum margin at final epoch for easy samples
   258          gamma: controls margin progression rate over epochs
   259          
AssistantStep 4test
Tool ResultStep 4
[Test #2] (1 test remaining; call submit(n=N) to choose which test result to submit as final)

### resnet56-cifar100 (scripts/resnet56_cifar100.sh)
Training progress (last epochs):
TRAIN_METRICS: epoch=160 train_loss=0.3599 train_acc=87.82 test_loss=1.2561 test_acc=67.41 lr=0.009549
TRAIN_METRICS: epoch=170 train_loss=0.2090 train_acc=92.86 test_loss=1.1764 test_acc=69.78 lr=0.005450
TRAIN_METRICS: epoch=180 train_loss=0.1022 train_acc=96.72 test_loss=1.1170 test_acc=72.03 lr=0.002447
TRAIN_METRICS: epoch=190 train_loss=0.0554 train_acc=98.44 test_loss=1.0999 test_acc=72.36 lr=0.000616
TRAIN_METRICS: epoch=200 train_loss=0.0443 train_acc=98.85 test_loss=1.0977 test_acc=72.51 lr=0.000000
Final metrics (resnet56-cifar100): test_acc_resnet56-cifar100=72.62

### vgg16bn-cifar100 (scripts/vgg16bn_cifar100.sh)
Training progress (last epochs):
TRAIN_METRICS: epoch=160 train_loss=0.1845 train_acc=93.67 test_loss=1.4075 test_acc=67.99 lr=0.009549
TRAIN_METRICS: epoch=170 train_loss=0.0667 train
AssistantStep 5edit
Tool Input
1{
2  "op": "replace",
3  "filename": "pytorch-vision/custom_loss.py",
4  "start_line": 246,
5  "end_line": 317,
6  "content": "def compute_loss(logits, targets, config):\n    \"\"\"Curriculum PolyLoss with Adaptive Smoothing.\n\n    Combines:\n    1. Label smoothing (fixed epsilon).\n    2. Poly loss term with curriculum: epsilon decreases over epochs.\n    3. Adaptive temperature scaling.\n\n    Loss = CE_smoothed + epsilon * (1 - pt)\n    where epsilon = base_epsilon * (1 - progress)^gamma\n    and temperature = 1 + tau * (1 - progress)\n\n    Hyperparameters:\n        smoothing_eps: label smoothing factor\n        base_epsilon: maximum poly weight at start\n        gamma: controls decay rate of poly weight\n        tau: temperature scaling magnitude\n    \"\"\"\n    # Hyperparameters (hardcoded)\n    smoothing_eps = 0.1\n    base_epsilon = 2.0\n    gamma = 0.5\n    tau = 0.5\n\n    num_classes = config['num_classes']\n    epoch = config['epoch']\n    total_epochs = config['total_epochs']\n\n    # Curriculum progression factor (0 to 1)\n    progress = epoch / max(total_epochs - 1, 1)  # avoid division by zero\n\n    # Adaptive temperature: starts warm (higher temp), ends cool (lower temp)\n    temperature = 1.0 + tau * (1.0 - progress)  # temperature decreases as progress increases\n\n    # Apply temperature scaling\n    logits_scaled = logits / temperature\n\n    # Compute probabilities\n    probs = F.softmax(logits_scaled, dim=-1)\n    pt = probs[range(len(targets)), targets]  # probability of true class\n\n    # Label smoothing target distribution\n    one_hot = F.one_hot(targets, num_classes).float()\n    smoothed_targets = (1.0 - smoothing_eps) * one_hot + smoothing_eps / num_classes\n\n    # Cross-entropy with smoothed targets\n    log_probs = F.log_softmax(logits_scaled, dim=-1)\n    ce = -(smoothed_targets * log_probs).sum(dim=-1)  # [B]\n\n    # Curriculum poly weight\n    epsilon = base_epsilon * ((1.0 - progress) ** gamma)\n    poly_term = epsilon * (1.0 - pt)\n\n    # Total loss\n    loss = (ce + poly_term).mean()\n\n    return loss"
7}
Tool ResultStep 5
OK: Replaced lines 246..317 with 57 line(s) in pytorch-vision/custom_loss.py. Editable range: 246–302.

[Current file: pytorch-vision/custom_loss.py | editable: 246–302 | total: 472 lines]
   243| # ============================================================================
   244| 
   245| # -- EDITABLE REGION START (lines 246-266) ------------------------------------
   246  def compute_loss(logits, targets, config):
   247      """Curriculum PolyLoss with Adaptive Smoothing.
   248  
   249      Combines:
   250      1. Label smoothing (fixed epsilon).
   251      2. Poly loss term with curriculum: epsilon decreases over epochs.
   252      3. Adaptive temperature scaling.
   253  
   254      Loss = CE_smoothed + epsilon * (1 - pt)
   255      where epsilon = base_epsilon * (1 - progress)^gamma
   256      and temperature = 1 + tau * (1 - progress)
   257  
   258      Hyperparameters:
   259          smoothing_eps: label smoothing factor
   260          base_epsilon: maximum poly
AssistantStep 6test
Tool ResultStep 6
[Test #3] (0 tests remaining; call submit(n=N) to choose which test result to submit as final)

[NOTE] This was your last test. You MUST now call submit(n=X) to choose which test result to submit as your final answer.

### resnet56-cifar100 (scripts/resnet56_cifar100.sh)
Training progress (last epochs):
TRAIN_METRICS: epoch=160 train_loss=1.4335 train_acc=88.03 test_loss=1.3021 test_acc=68.31 lr=0.009549
TRAIN_METRICS: epoch=170 train_loss=1.2331 train_acc=92.62 test_loss=1.2605 test_acc=69.79 lr=0.005450
TRAIN_METRICS: epoch=180 train_loss=1.0710 train_acc=96.41 test_loss=1.1836 test_acc=72.39 lr=0.002447
TRAIN_METRICS: epoch=190 train_loss=0.9820 train_acc=98.11 test_loss=1.1619 test_acc=73.26 lr=0.000616
TRAIN_METRICS: epoch=200 train_loss=0.9132 train_acc=98.43 test_loss=1.1748 test_acc=73.07 lr=0.000000
Final metrics (resnet56-cifar100): test_acc_resnet56-cifar100=73.33

### vgg16bn-cifar100 (scripts/vgg16bn_cifar100.sh)
Training progress (last epochs):
TRAIN_METRICS: epoch=160 tr
AssistantStep 7submit
Tool Input
1{
2  "n": 1
3}
Tool ResultStep 7
[submit] Submitting result from test #1 as final.

### resnet56-cifar100 (scripts/resnet56_cifar100.sh)
Training progress (last epochs):
TRAIN_METRICS: epoch=160 train_loss=0.3967 train_acc=87.46 test_loss=1.3638 test_acc=67.49 lr=0.009549
TRAIN_METRICS: epoch=170 train_loss=0.2423 train_acc=92.55 test_loss=1.2600 test_acc=69.82 lr=0.005450
TRAIN_METRICS: epoch=180 train_loss=0.1203 train_acc=96.70 test_loss=1.1875 test_acc=72.03 lr=0.002447
TRAIN_METRICS: epoch=190 train_loss=0.0667 train_acc=98.40 test_loss=1.1575 test_acc=72.46 lr=0.000616
TRAIN_METRICS: epoch=200 train_loss=0.0538 train_acc=98.86 test_loss=1.1574 test_acc=72.65 lr=0.000000
Final metrics (resnet56-cifar100): test_acc_resnet56-cifar100=72.66

### vgg16bn-cifar100 (scripts/vgg16bn_cifar100.sh)
Training progress (last epochs):
TRAIN_METRICS: epoch=160 train_loss=0.1947 train_acc=93.73 test_loss=1.4635 test_acc=68.79 lr=0.009549
TRAIN_METRICS: epoch=170 train_loss=0.0744 train_acc=97.57 test_loss=1.3883 test_acc=72.03 l