Merge pull request #54 from codelion/fix-multi-class-learning

fix multi class learning

Author: codelion

setup.py

@@ -15,7 +15,7 @@
 
 setup(
     name="adaptive-classifier",
-    version="0.0.16",
+    version="0.0.17",
     author="codelion",
     author_email="codelion@okyasoft.com",
     description="A flexible, adaptive classification system for dynamic text classification",

src/adaptive_classifier/__init__.py

@@ -3,22 +3,7 @@
 from .memory import PrototypeMemory
 from huggingface_hub import ModelHubMixin
 
-import os
-import re
-
-def get_version_from_setup():
-    try:
-        setup_path = os.path.join(os.path.dirname(os.path.dirname(__file__)), 'setup.py')
-        with open(setup_path, 'r') as f:
-            content = f.read()
-            version_match = re.search(r'version=["\']([^"\']+)["\']', content)
-            if version_match:
-                return version_match.group(1)
-    except Exception:
-        pass
-    return "unknown"
-
-__version__ = get_version_from_setup()
+__version__ = "0.0.17"
 
 __all__ = [
     "AdaptiveClassifier",

src/adaptive_classifier/classifier.py

@@ -83,48 +83,67 @@ def add_examples(self, texts: List[str], labels: List[str]):
             raise ValueError("Empty input lists")
         if len(texts) != len(labels):
             raise ValueError("Mismatched text and label lists")
-        
+
+        # Check if classifier has any existing classes (before updating mappings)
+        has_existing_classes = len(self.label_to_id) > 0
+
         # Check for new classes
         new_classes = set(labels) - set(self.label_to_id.keys())
         is_adding_new_classes = len(new_classes) > 0
-        
+
         # Update label mappings - sort new classes alphabetically for consistent IDs
         for label in sorted(new_classes):
             idx = len(self.label_to_id)
             self.label_to_id[label] = idx
             self.id_to_label[idx] = label
-        
+
         # Get embeddings for all texts
         embeddings = self._get_embeddings(texts)
-        
+
         # Add examples to memory and update training history
         for text, embedding, label in zip(texts, embeddings, labels):
             example = Example(text, label, embedding)
             self.memory.add_example(example, label)
-            
+
             # Update training history
             if label not in self.training_history:
                 self.training_history[label] = 0
             self.training_history[label] += 1
-        
-        # Special handling for new classes
-        if is_adding_new_classes:
-            # Store old head for EWC
+
+        # Determine training strategy: only use special new class handling for incremental learning
+        is_incremental_learning = is_adding_new_classes and has_existing_classes
+
+        if is_incremental_learning:
+            # Adding new classes to existing classifier - use special handling
+            # Store old head for EWC before modifying structure
             old_head = copy.deepcopy(self.adaptive_head) if self.adaptive_head is not None else None
-            
-            # Initialize new head with more output classes
-            self._initialize_adaptive_head()
-            
+
+            # Expand existing head to accommodate new classes (preserves weights)
+            num_classes = len(self.label_to_id)
+            self.adaptive_head.update_num_classes(num_classes)
+            # Move to correct device after update
+            self.adaptive_head = self.adaptive_head.to(self.device)
+
             # Train with focus on new classes
             self._train_new_classes(old_head, new_classes)
         else:
-            # Regular training for existing classes
+            # Initial training or regular updates - use normal training
+            # Initialize head if needed
+            if self.adaptive_head is None:
+                self._initialize_adaptive_head()
+            elif is_adding_new_classes:
+                # Edge case: expanding head for new classes but treating as regular training
+                num_classes = len(self.label_to_id)
+                self.adaptive_head.update_num_classes(num_classes)
+                self.adaptive_head = self.adaptive_head.to(self.device)
+
+            # Regular training
             self._train_adaptive_head()
-            
+
             # Strategic training step if enabled
             if self.strategic_mode and self.train_steps % self.config.strategic_training_frequency == 0:
                 self._perform_strategic_training()
-        
+
         # Ensure FAISS index is up to date after adding examples
         self.memory._rebuild_index()
 
@@ -142,48 +161,94 @@ def _train_new_classes(self, old_head: Optional[nn.Module], new_classes: Set[str
         for label in self.memory.examples:
             examples_per_class[label] = len(self.memory.examples[label])
 
-        # Calculate sampling weights to balance old and new classes
+        # Improved sampling strategy for many-class scenarios
         min_examples = min(examples_per_class.values())
-        sampling_weights = {}
-        
-        for label, count in examples_per_class.items():
-            if label in new_classes:
-                # Oversample new classes
-                sampling_weights[label] = 2.0
-            else:
-                # Sample old classes proportionally
-                sampling_weights[label] = min_examples / count
-        
-        # Sample examples with weights
-        for label, examples in self.memory.examples.items():
-            weight = sampling_weights[label]
-            num_samples = max(min_examples, int(len(examples) * weight))
-            
-            # Randomly sample with replacement if needed
-            indices = np.random.choice(
-                len(examples),
-                size=num_samples,
-                replace=num_samples > len(examples)
-            )
-            
-            for idx in indices:
-                example = examples[idx]
-                all_embeddings.append(example.embedding)
-                all_labels.append(self.label_to_id[label])
+        max_examples = max(examples_per_class.values())
+
+        # For many-class scenarios, use a more balanced approach
+        num_classes = len(examples_per_class)
+        target_samples_per_class = max(5, min(10, min_examples * 2))  # Adaptive target
+
+        if num_classes > 20:  # Many-class scenario
+            # Use stratified sampling to ensure all classes get representation
+            for label, examples in self.memory.examples.items():
+                if label in new_classes:
+                    # Give new classes more representation, but not excessive
+                    num_samples = min(len(examples), target_samples_per_class * 2)
+                else:
+                    # Ensure old classes maintain representation
+                    num_samples = min(len(examples), target_samples_per_class)
+
+                # Sample without replacement first, then with if needed
+                if num_samples <= len(examples):
+                    indices = np.random.choice(len(examples), size=num_samples, replace=False)
+                else:
+                    indices = np.random.choice(len(examples), size=num_samples, replace=True)
+
+                for idx in indices:
+                    example = examples[idx]
+                    all_embeddings.append(example.embedding)
+                    all_labels.append(self.label_to_id[label])
+        else:
+            # Original strategy for fewer classes
+            sampling_weights = {}
+
+            for label, count in examples_per_class.items():
+                if label in new_classes:
+                    # Oversample new classes
+                    sampling_weights[label] = 2.0
+                else:
+                    # Sample old classes proportionally
+                    sampling_weights[label] = min_examples / count
+
+            # Sample examples with weights
+            for label, examples in self.memory.examples.items():
+                weight = sampling_weights[label]
+                num_samples = max(min_examples, int(len(examples) * weight))
+
+                # Randomly sample with replacement if needed
+                indices = np.random.choice(
+                    len(examples),
+                    size=num_samples,
+                    replace=num_samples > len(examples)
+                )
+
+                for idx in indices:
+                    example = examples[idx]
+                    all_embeddings.append(example.embedding)
+                    all_labels.append(self.label_to_id[label])
 
         all_embeddings = torch.stack(all_embeddings)
         all_labels = torch.tensor(all_labels)
 
         # Create dataset and initialize EWC with lower penalty for new classes
         dataset = torch.utils.data.TensorDataset(all_embeddings, all_labels)
-        
+
+        ewc = None
         if old_head is not None:
-            ewc = EWC(
-                old_head,
-                dataset,
-                device=self.device,
-                ewc_lambda=10.0  # Lower EWC penalty to allow better learning of new classes
-            )
+            # Create a dataset for EWC that only includes examples from old classes
+            old_embeddings = []
+            old_labels = []
+            old_label_to_id = {label: idx for idx, label in enumerate(self.id_to_label.values())
+                               if label not in new_classes}
+
+            for label, examples in self.memory.examples.items():
+                if label not in new_classes:  # Only old classes
+                    for example in examples[:5]:  # Limit to representative examples
+                        old_embeddings.append(example.embedding)
+                        old_labels.append(old_label_to_id[label])
+
+            if old_embeddings:  # Only create EWC if we have old examples
+                old_embeddings = torch.stack(old_embeddings)
+                old_labels = torch.tensor(old_labels, dtype=torch.long)
+                old_dataset = torch.utils.data.TensorDataset(old_embeddings, old_labels)
+
+                ewc = EWC(
+                    old_head,
+                    old_dataset,
+                    device=self.device,
+                    ewc_lambda=5.0  # Balanced EWC penalty
+                )
 
         # Training setup
         self.adaptive_head.train()
@@ -220,7 +285,7 @@ def _train_new_classes(self, old_head: Optional[nn.Module], new_classes: Set[str
                 task_loss = criterion(outputs, batch_labels)
 
                 # Add EWC loss if applicable
-                if old_head is not None:
+                if ewc is not None:
                     ewc_loss = ewc.ewc_loss(batch_size=len(batch_embeddings))
                     loss = task_loss + ewc_loss
                 else:
@@ -302,10 +367,12 @@ def _predict_regular(self, text: str, k: int = 5) -> List[Tuple[str, float]]:
             # Get embedding
             embedding = self._get_embeddings([text])[0]
 
-            # Get prototype predictions
-            proto_preds = self.memory.get_nearest_prototypes(embedding, k=k)
-            
-            # Get neural predictions if available
+            # Get prototype predictions for ALL classes (not limited by k)
+            # This ensures complete scoring information for proper combination
+            max_classes = len(self.id_to_label) if self.id_to_label else k
+            proto_preds = self.memory.get_nearest_prototypes(embedding, k=max_classes)
+
+            # Get neural predictions if available for ALL classes (not limited by k)
             if self.adaptive_head is not None:
                 self.adaptive_head.eval()  # Ensure eval mode
                 # Add batch dimension and move to device
@@ -314,8 +381,9 @@ def _predict_regular(self, text: str, k: int = 5) -> List[Tuple[str, float]]:
                 # Squeeze batch dimension
                 logits = logits.squeeze(0)
                 probs = F.softmax(logits, dim=0)
-                
-                values, indices = torch.topk(probs, min(k, len(self.id_to_label)))
+
+                # Get predictions for ALL classes for proper scoring combination
+                values, indices = torch.topk(probs, len(self.id_to_label))
                 head_preds = [
                     (self.id_to_label[idx.item()], val.item())
                     for val, idx in zip(values, indices)