address PR code review

src/axolotl/integrations/aux_free_router/__init__.py

@@ -4,6 +4,6 @@ from .args import AuxFreeRouterArgs
 from .plugin import AuxFreeMoEPlugin
 
 __all__ = [
-    "AuxFreeRouterArgs",
     "AuxFreeMoEPlugin",
+    "AuxFreeRouterArgs",
 ]

src/axolotl/integrations/aux_free_router/adapters.py

@@ -88,12 +88,22 @@ class BaseMoEAdapter:
             try:
                 model_or_layer.router_aux_loss_coef = 0.0
             except Exception:  # pragma: no cover - non-critical
-                pass
+                LOG.debug(
+                    "disable_aux_loss: failed to set router_aux_loss_coef on %s",
+                    type(model_or_layer).__name__,
+                    exc_info=True,
+                )
 
     def _register_aux_buffers(
         self, moe_layer: nn.Module, handle: LayerHandle, shim: AuxFreeShim
     ) -> None:
-        device = next(moe_layer.parameters(), torch.tensor(0)).device
+        p = next(moe_layer.parameters(), None)
+        b = next(moe_layer.buffers(), None)
+        device = (
+            p.device
+            if p is not None
+            else (b.device if b is not None else torch.device("cpu"))
+        )
         if not hasattr(moe_layer, "_afb_bias"):
             moe_layer.register_buffer(
                 "_afb_bias", torch.zeros(handle.num_experts, device=device)
@@ -275,7 +285,7 @@ class BailingAdapter(BaseMoEAdapter):
             scores_unbiased = torch.sigmoid(logits.float()).to(logits.dtype)
             bias = moe_layer._afb_bias
             biased_scores = scores_unbiased + bias
-            topk_vals, topk_idx = self.group_limited_topk(biased_scores)
+            _, topk_idx = self.group_limited_topk(biased_scores)
             weights = torch.gather(scores_unbiased, 1, topk_idx)
             if self.top_k > 1:
                 denom = weights.sum(dim=-1, keepdim=True).clamp_min_(1e-20)
@@ -376,6 +386,8 @@ def discover_and_prepare_layers(
         idx += 1
 
     LOG.info(
-        f"AuxFreeMoE: prepared {len(handles)} {adapter.family} layers for aux-free routing"
+        "AuxFreeMoE: prepared %d %s layers for aux-free routing",
+        len(handles),
+        adapter.family,
     )
     return handles

src/axolotl/integrations/aux_free_router/args.py

@@ -37,14 +37,14 @@ class AuxFreeRouterArgs(BaseModel):
     moe_update_rate: float | None = Field(
         default=None,
         json_schema_extra={
-            "description": "Per-step bias update rate (gamma). Recommended: 0.005–0.05. "
+            "description": "Per-step bias update rate (gamma). Recommended: 0.005-0.05. "
             "If unset, plugin default is 0.01."
         },
     )
     moe_update_momentum: float | None = Field(
         default=None,
         json_schema_extra={
-            "description": "EMA momentum for expert load smoothing (0–1). "
+            "description": "EMA momentum for expert load smoothing (0-1). "
             "If unset, plugin default is 0.9."
         },
     )

src/axolotl/integrations/aux_free_router/core.py

@@ -67,7 +67,7 @@ class AuxFreeShim:
         else:
             b = self.state.bias[layer_idx]
         biased = logits + b  # bias is a buffer
-        topk_scores, topk_idx = torch.topk(biased, k=top_k, dim=-1)
+        _topk_scores, topk_idx = torch.topk(biased, k=top_k, dim=-1)
         chosen_logits = torch.gather(logits, -1, topk_idx)
         weights = torch.softmax(chosen_logits.float(), dim=-1).to(logits.dtype)
         return topk_idx, weights

src/axolotl/integrations/aux_free_router/plugin.py

@@ -239,11 +239,17 @@ class AuxFreeMoEPlugin(BasePlugin):
             return dist.group.WORLD
 
         rank = dist.get_rank()
-        group_start = (rank // ep_size) * ep_size
+        # All ranks must collectively create all EP subgroups in the same order
+        # to avoid deadlocks (dist.new_group is a collective operation).
+        world_size = world
+        my_group = None
+        for group_start in range(0, world_size, ep_size):
             ranks = tuple(range(group_start, group_start + ep_size))
             if ranks not in self._ep_group_cache:
                 self._ep_group_cache[ranks] = dist.new_group(ranks)
-        return self._ep_group_cache[ranks]
+            if rank in ranks:
+                my_group = self._ep_group_cache[ranks]
+        return my_group
 
     def add_callbacks_post_trainer(self, cfg, trainer):
         if getattr(cfg, "moe_balance_type", None) != "noaux_tc":

src/axolotl/integrations/kernels/sonicmoe/routing.py

@@ -177,7 +177,9 @@ def softmax_group_topk_routing(
         score_mask = (
             group_mask.unsqueeze(-1).expand(-1, n_group, E // n_group).reshape(-1, E)
         )
-        scores_for_choice = scores_for_choice.masked_fill(~score_mask.bool(), 0.0)
+        scores_for_choice = scores_for_choice.masked_fill(
+            ~score_mask.bool(), -float("inf")
+        )
 
     topk_indices = torch.topk(scores_for_choice, k=K, dim=-1, sorted=False)[1]
     topk_weights = router_probs.gather(1, topk_indices)
@@ -275,7 +277,9 @@ def sigmoid_topk_routing(
         score_mask = (
             group_mask.unsqueeze(-1).expand(-1, n_group, E // n_group).reshape(-1, E)
         )
-        scores_for_choice = scores_for_choice.masked_fill(~score_mask.bool(), 0.0)
+        scores_for_choice = scores_for_choice.masked_fill(
+            ~score_mask.bool(), -float("inf")
+        )
 
     # Final topk from (possibly masked) scores
     topk_indices = torch.topk(scores_for_choice, k=K, dim=-1, sorted=False)[1]
@@ -316,6 +320,8 @@ def _accumulate_afb_counts(moe_block, topk_indices: torch.Tensor) -> None:
     ``aux_free_router`` plugin).  The counts are later consumed by the
     ``MoeAuxFreeBiasUpdateCallback`` at each training step.
     """
+    if hasattr(moe_block, "training") and not moe_block.training:
+        return
     afb_counts = getattr(moe_block, "_afb_counts", None)
     if afb_counts is None:
         return

tests/e2e/test_llama4_moe_aux_free.py

@@ -21,7 +21,7 @@ class TestLlama4MoeAuxFree(unittest.TestCase):
             {
                 "base_model": "yujiepan/llama-4-tiny-random",
                 "tokenizer_config": "yujiepan/llama-4-tiny-random",
-                "trust_remote_code": True,
+                "trust_remote_code": False,
                 "flash_attention": False,
                 "sequence_len": 512,
                 "bf16": False,

tests/e2e/test_moe_aux_parity.py

@@ -3,8 +3,11 @@ Parity test comparing aux-loss (gshard) vs aux-loss-free (noaux_tc) on Mixtral-t
 Checks that aux-free training loss does not degrade beyond a small tolerance.
 """
 
+import gc
 import unittest
 
+import torch
+
 from axolotl.common.datasets import load_datasets
 from axolotl.train import train
 from axolotl.utils.config import normalize_config, prepare_plugins, validate_config
@@ -61,6 +64,11 @@ class TestMoeAuxParity(unittest.TestCase):
         loss0 = _last_logged_loss(trainer0)
         assert loss0 is not None
 
+        # Release baseline resources before starting aux-free run
+        del model0, trainer0, dataset_meta0
+        gc.collect()
+        torch.cuda.empty_cache()
+
         # Aux-free: plugin + noaux_tc
         cfg1 = DictDefault(dict(base_cfg))
         cfg1.output_dir = f"{temp_dir}/auxfree"

tests/unit/test_aux_free_adapters.py

@@ -390,7 +390,9 @@ class TestAuxFreeAdapters(unittest.TestCase):
 
     def test_ep_group_resolution_deferred_until_dist_ready(self):
         if dist.is_available() and dist.is_initialized():
-            dist.destroy_process_group()
+            self.skipTest(
+                "Cannot safely test deferred EP group resolution when a process group is already initialized"
+            )
 
         model, block = _build_bailing_model()
         cfg = _cfg(moe_bias_sync_group="ep", expert_parallel_size=1)