fix twice gradient cut

model_training_nnn_tpu/ISSUES.md

@@ -0,0 +1,36 @@
+# ISSUES
+
+## 双重梯度裁剪  
+优化器级别：global_clipnorm=self.args.get('grad_norm_clip_value', 0.0)（第283行）
+手动级别：tf.clip_by_global_norm（第447-449行）
+这导致梯度被裁剪两次，并且在TPU的分布式训练中可能引发内部状态冲突。
+
+修复总结
+问题根源：双重梯度裁剪导致AdamW内部状态冲突 修复内容：
+移除了优化器级别的梯度裁剪：删除了 global_clipnorm 参数
+保留手动梯度裁剪：在 _train_step 中继续使用 tf.clip_by_global_norm
+为什么会出错：
+```python
+# 之前：双重裁剪
+optimizer = tf.keras.optimizers.AdamW(
+    global_clipnorm=clip_value  # 第一次裁剪
+)
+```
+```python
+# 在 _train_step 中：
+tf.clip_by_global_norm(gradients, clip_value)  # 第二次裁剪
+optimizer.apply_gradients(...)  # 内部再次处理，导致冲突
+现在的修复：
+```
+```python
+# 现在：只有一次裁剪
+optimizer = tf.keras.optimizers.AdamW(
+    # 没有 global_clipnorm
+)
+
+```
+```python
+# 在 _train_step 中：
+tf.clip_by_global_norm(gradients, clip_value)  # 唯一的裁剪
+optimizer.apply_gradients(...)  # 正常工作
+```

model_training_nnn_tpu/trainer_tf.py

@@ -88,9 +88,7 @@ class BrainToTextDecoderTrainerTF:
 
         # Build model within strategy scope
         with self.strategy.scope():
-            print("🔨 Building model within TPU strategy scope...")
             self.model = self._build_model()
-            print("⚙️ Creating optimizer...")
             self.optimizer = self._create_optimizer()
             print("🔧 Pre-building optimizer state for TPU...")
             # For TPU, we must ensure optimizer is completely ready before training
@@ -125,13 +123,8 @@ class BrainToTextDecoderTrainerTF:
                 print(f"Full traceback: {traceback.format_exc()}")
                 raise RuntimeError(f"Optimizer pre-build failed: {e}") from e
 
-            print("📅 Setting up learning rate scheduler...")
             self.lr_scheduler = self._create_lr_scheduler()
-            print("✅ LR scheduler ready")
-
-            print("🎯 Initializing CTC loss...")
             self.ctc_loss = CTCLoss(blank_index=0, reduction='none')
-            print("✅ CTC loss initialized")
 
         # Log model information
         self._log_model_info()
@@ -452,12 +445,9 @@ class BrainToTextDecoderTrainerTF:
                 beta_1=self.args['beta0'],
                 beta_2=self.args['beta1'],
                 epsilon=self.args['epsilon'],
-                weight_decay=0.0,  # Disabled for TPU compatibility
-                # TPU-specific settings
-                global_clipnorm=self.args.get('grad_norm_clip_value', 0.0) if self.args.get('grad_norm_clip_value', 0.0) > 0 else None
+                weight_decay=0.0  # Disabled for TPU compatibility
+                # REMOVE global_clipnorm to avoid double clipping with manual tf.clip_by_global_norm
             )
-            print(f"⚠️  Weight decay disabled for TPU compatibility (was {self.args['weight_decay']})")
-            print("💡 Consider implementing manual L2 regularization if needed")
         else:
             print("Using standard optimizer configuration")
             optimizer = tf.keras.optimizers.AdamW(