Merge branch 'rc-debug-underflow' into 'main'

Rc debug underflow

See merge request ADLR/megatron-lm!246

megatron/arguments.py

@@ -308,6 +308,8 @@ def _add_logging_args(parser):
 
     group.add_argument('--log-params-norm', action='store_true',
                        help='If set, calculate and log parameters norm.')
+    group.add_argument('--log-num-zeros-in-grad', action='store_true',
+                       help='If set, calculate and log the number of zeros in gradient.')
     group.add_argument('--tensorboard-log-interval', type=int, default=1,
                        help='Report to tensorboard interval.')
     group.add_argument('--tensorboard-queue-size', type=int, default=1000,

megatron/optimizer/__init__.py

@@ -84,7 +84,7 @@ def get_megatron_optimizer(model):
                 hysteresis=args.hysteresis)
         # Megatron optimizer.
         return FP16OptimizerWithFP16Params(optimizer, grad_scaler,
-                                           args.clip_grad)
+                                           args.clip_grad, args.log_num_zeros_in_grad)
 
     # FP32.
-    return FP32Optimizer(optimizer, args.clip_grad)
+    return FP32Optimizer(optimizer, args.clip_grad, args.log_num_zeros_in_grad)

megatron/optimizer/clip_grads.py

@@ -118,3 +118,31 @@ def clip_grad_norm_fp32(parameters, max_norm, norm_type=2):
                              clip_coeff)
 
     return total_norm
+
+
+def count_zeros_fp32(parameters):
+
+    if isinstance(parameters, torch.Tensor):
+        parameters = [parameters]
+
+    # Filter parameters based on:
+    #   - grad should not be none
+    #   - parameter should not be shared
+    #   - should not be a replica due to tensor model parallelism
+    total_num_zeros = 0.0
+    for param in parameters:
+        grad_not_none = param.grad is not None
+        is_not_shared = param_is_not_shared(param)
+        is_not_tp_duplicate = param_is_not_tensor_parallel_duplicate(param)
+        if grad_not_none and is_not_shared and is_not_tp_duplicate:
+            grad = param.grad.detach()
+            num_zeros = grad.numel() - torch.count_nonzero(grad)
+            total_num_zeros = num_zeros + total_num_zeros
+
+    # Sum across all model-parallel GPUs.
+    torch.distributed.all_reduce(total_num_zeros,
+                                 op=torch.distributed.ReduceOp.SUM,
+                                 group=mpu.get_model_parallel_group())
+    total_num_zeros = total_num_zeros.item()
+
+    return total_num_zeros

megatron/optimizer/optimizer.py

@@ -27,7 +27,7 @@ from megatron import get_timers
 from megatron import mpu
 from megatron import print_rank_0
 
-from .clip_grads import clip_grad_norm_fp32
+from .clip_grads import clip_grad_norm_fp32, count_zeros_fp32
 
 
 def _zero_grad_group_helper(group, set_to_none):
@@ -65,13 +65,21 @@ class MegatronOptimizer(ABC):
         self.optimizer = optimizer
         assert self.optimizer, 'no optimizer is provided.'
 
-    def clip_grad_norm(self, clip_grad):
+    def get_parameters(self):
         params = []
         for param_group in self.optimizer.param_groups:
             for param in param_group['params']:
                 params.append(param)
+        return params
+
+    def clip_grad_norm(self, clip_grad):
+        params = self.get_parameters()
         return clip_grad_norm_fp32(params, clip_grad)
 
+    def count_zeros(self):
+        params = self.get_parameters()
+        return count_zeros_fp32(params)
+
     @abstractmethod
     def zero_grad(self, set_to_none=True):
         pass
@@ -131,11 +139,12 @@ class MegatronOptimizer(ABC):
 
 class FP16OptimizerWithFP16Params(MegatronOptimizer):
 
-    def __init__(self, optimizer, grad_scaler, clip_grad):
+    def __init__(self, optimizer, grad_scaler, clip_grad, log_num_zeros_in_grad):
         super(FP16OptimizerWithFP16Params, self).__init__(optimizer)
 
         self.grad_scaler = grad_scaler
         self.clip_grad = clip_grad
+        self.log_num_zeros_in_grad = log_num_zeros_in_grad
 
         # Tensor used to determine if a nan/if has happend.
         # Any non-zero value indicates inf/nan.
@@ -289,7 +298,6 @@ class FP16OptimizerWithFP16Params(MegatronOptimizer):
     def reload_model_params(self):
         self._copy_model_params_to_main_params()
 
-
     @torch.no_grad()
     def step(self):
 
@@ -311,7 +319,7 @@ class FP16OptimizerWithFP16Params(MegatronOptimizer):
 
         # If we found inf/nan, skip the update.
         if found_inf_flag:
-            return False, None
+            return False, None, None
 
         # Clip the main gradients.
         timers('optimizer-clip-main-grad').start()
@@ -320,6 +328,9 @@ class FP16OptimizerWithFP16Params(MegatronOptimizer):
             grad_norm = self.clip_grad_norm(self.clip_grad)
         timers('optimizer-clip-main-grad').stop()
 
+        # count the zeros in the grads
+        num_zeros_in_grad = self.count_zeros() if self.log_num_zeros_in_grad else None
+
         # Step the optimizer.
         self.optimizer.step()
 
@@ -329,7 +340,7 @@ class FP16OptimizerWithFP16Params(MegatronOptimizer):
         timers('optimizer-copy-main-to-model-params').stop()
 
         # Successful update.
-        return True, grad_norm
+        return True, grad_norm, num_zeros_in_grad
 
 
     def state_dict(self):
@@ -370,10 +381,11 @@ class FP16OptimizerWithFP16Params(MegatronOptimizer):
 
 class FP32Optimizer(MegatronOptimizer):
 
-    def __init__(self, optimizer, clip_grad):
+    def __init__(self, optimizer, clip_grad, log_num_zeros_in_grad):
 
         super(FP32Optimizer, self).__init__(optimizer)
         self.clip_grad = clip_grad
+        self.log_num_zeros_in_grad = log_num_zeros_in_grad
         self._scale = torch.cuda.FloatTensor([1.0])
 
 
@@ -398,11 +410,14 @@ class FP32Optimizer(MegatronOptimizer):
         if self.clip_grad > 0.0:
             grad_norm = self.clip_grad_norm(self.clip_grad)
 
+        # count the zeros in the grads
+        num_zeros_in_grad = self.count_zeros() if self.log_num_zeros_in_grad else None
+
         # Update parameters.
         self.optimizer.step()
 
         # No overflow for FP32 optimizer.
-        return True, grad_norm
+        return True, grad_norm, num_zeros_in_grad
 
 
     def reload_model_params(self):

megatron/training.py

@@ -378,7 +378,7 @@ def train_step(forward_step_func, data_iterator,
 
     # Update parameters.
     timers('optimizer').start()
-    update_successful, grad_norm = optimizer.step()
+    update_successful, grad_norm, num_zeros_in_grad = optimizer.step()
     timers('optimizer').stop()
 
     # Update learning rate.
@@ -397,13 +397,13 @@ def train_step(forward_step_func, data_iterator,
         for key in losses_reduced[0]:
             losses_reduced_for_key = [x[key] for x in losses_reduced]
             loss_reduced[key] = sum(losses_reduced_for_key) / len(losses_reduced_for_key)
-        return loss_reduced, skipped_iter, grad_norm
-    return {}, skipped_iter, grad_norm
+        return loss_reduced, skipped_iter, grad_norm, num_zeros_in_grad
+    return {}, skipped_iter, grad_norm, num_zeros_in_grad
 
 
 def training_log(loss_dict, total_loss_dict, learning_rate, iteration,
                  loss_scale, report_memory_flag, skipped_iter,
-                 grad_norm, params_norm):
+                 grad_norm, params_norm, num_zeros_in_grad):
     """Log training information such as losses, timing, ...."""
     args = get_args()
     timers = get_timers()
@@ -492,6 +492,10 @@ def training_log(loss_dict, total_loss_dict, learning_rate, iteration,
             writer.add_scalar('grad-norm', grad_norm, iteration)
             writer.add_scalar('grad-norm vs samples', grad_norm,
                               args.consumed_train_samples)
+        if num_zeros_in_grad is not None:
+            writer.add_scalar('num-zeros', num_zeros_in_grad, iteration)
+            writer.add_scalar('num-zeros vs samples', num_zeros_in_grad,
+                              args.consumed_train_samples)
         if params_norm is not None:
             writer.add_scalar('params-norm', params_norm, iteration)
             writer.add_scalar('params-norm vs samples', params_norm,
@@ -526,6 +530,8 @@ def training_log(loss_dict, total_loss_dict, learning_rate, iteration,
         log_string += ' loss scale: {:.1f} |'.format(loss_scale)
         if grad_norm is not None:
             log_string += ' grad norm: {:.3f} |'.format(grad_norm)
+        if num_zeros_in_grad is not None:
+            log_string += ' num zeros: {:.1f} |'.format(num_zeros_in_grad)
         if params_norm is not None:
             log_string += ' params norm: {:.3f} |'.format(params_norm)
         log_string += ' number of skipped iterations: {:3d} |'.format(
@@ -581,7 +587,8 @@ def train(forward_step_func, model, optimizer, lr_scheduler,
     report_memory_flag = True
     while iteration < args.train_iters:
         update_num_microbatches(args.consumed_train_samples)
-        loss_dict, skipped_iter, grad_norm = train_step(forward_step_func,
+        loss_dict, skipped_iter, grad_norm, num_zeros_in_grad = \
+            train_step(forward_step_func,
                        train_data_iterator,
                        model,
                        optimizer,
@@ -600,7 +607,7 @@ def train(forward_step_func, model, optimizer, lr_scheduler,
                                           optimizer.param_groups[0]['lr'],
                                           iteration, loss_scale,
                                           report_memory_flag, skipped_iter,
-                                          grad_norm, params_norm)
+                                          grad_norm, params_norm, num_zeros_in_grad)
 
         # Autoresume
         if args.adlr_autoresume and \