[simplefsdp] fix & enable DSV3 manual bucketing

torchtitan/experiments/simple_fsdp/backend.py

@@ -8,6 +8,7 @@
 
 import torch
 import torch._functorch.config as functorch_config
+from functorch.compile import min_cut_rematerialization_partition
 from torchtitan.tools.logging import logger
 
 from .job_config import Compile as CompileConfig
@@ -60,6 +61,7 @@ def aot_eager_autobucketing_reordering_pass(
             backend = aot_autograd_backend(
                 fw_compiler=aot_eager_autobucketing_reordering_pass,
                 bw_compiler=aot_eager_autobucketing_reordering_pass,
+                partition_fn=min_cut_rematerialization_partition,
                 keep_inference_input_mutations=True,
             )
         elif compile_config.backend == "inductor":
@@ -108,6 +110,7 @@ def aot_eager_transformer_block_bucketing_reordering_pass(
             backend = aot_autograd_backend(
                 fw_compiler=aot_eager_transformer_block_bucketing_reordering_pass,
                 bw_compiler=aot_eager_transformer_block_bucketing_reordering_pass,
+                partition_fn=min_cut_rematerialization_partition,
                 keep_inference_input_mutations=True,
             )
         elif compile_config.backend == "inductor":

torchtitan/experiments/simple_fsdp/deepseek_v3/parallelize.py

@@ -30,17 +30,20 @@ def get_transformer_block_buckets(model) -> list[list[str] | str]:
         [model.norm, model.output],
     ]
     for layer_id, transformer_block in model.layers.items():
-        # [TODO](ruisizhang123) add EP support for transformer block bucketing
         module_list.append(transformer_block)
 
     def convert_modules_to_fqns(modules, module_to_fqn_mapping):
         """Convert a (possibly nested) list of modules to FQN strings."""
         result = []
         for m in modules:
             if isinstance(m, list):
-                result.append(convert_modules_to_fqns(m, module_to_fqn_mapping))
+                # check if fqn_list is valid. In PP, bucketed module may
+                # not be in the current rank, and fqn_list is None.
+                if fqn_list := convert_modules_to_fqns(m, module_to_fqn_mapping):
+                    result.append(fqn_list)
             else:
-                result.append(module_to_fqn_mapping.get(m, None))
+                if fqn := module_to_fqn_mapping.get(m):
+                    result.append(fqn)
         return result
 
     module_to_name = {m: n for n, m in model.named_modules()}

torchtitan/experiments/simple_fsdp/llama3/parallelize.py

@@ -51,6 +51,8 @@ def convert_modules_to_fqns(modules, module_to_fqn_mapping):
         result = []
         for m in modules:
             if isinstance(m, list):
+                # check if fqn_list is valid. In PP, bucketed module may
+                # not be in the current rank, and fqn_list is None.
                 if fqn_list := convert_modules_to_fqns(m, module_to_fqn_mapping):
                     result.append(fqn_list)
             else:

torchtitan/experiments/simple_fsdp/reshard_after_forward.py

@@ -65,20 +65,40 @@ def force_recompute_node(node):
         # nearby ac_graph_id values
         node.meta["ac_graph_id"] = 100000
 
+    def tag_view_recompute_nodes(start_node, seen=None):
+        """
+        Recursively walk only *single‑user* paths from start_node,
+        tagging view nodes for recompute.
+        """
+        if seen is None:
+            seen = set()
+        if start_node in seen:
+            return
+        seen.add(start_node)
+
+        # If current node has multiple users, stop descending
+        if len(start_node.users) != 1:
+            return
+
+        user = next(iter(start_node.users))
+
+        # Only continue if this user is a view op
+        if user.op == "call_function" and user.target.is_view:
+            force_recompute_node(user)
+            # Recurse deeper only on this one user
+            tag_view_recompute_nodes(user, seen)
+
     # Make all-gather nodes (and related nodes) recomputable, to circumvent
     # https://github.com/pytorch/pytorch/issues/136433
     for node in graph.nodes:
         if is_wait_tensor_from_fsdp(node):
             ag_node = node.args[0]
             force_recompute_node(ag_node)  # all_gather
             force_recompute_node(node)  # wait_tensor
-            # Force-recompute slice that comes after wait
-            for user in node.users:
-                if (
-                    user.op == "call_function"
-                    and user.target == torch.ops.aten.slice.Tensor
-                ):
-                    force_recompute_node(user)
+
+            # Recursively tag view ops from all_gather_wait
+            tag_view_recompute_nodes(node)
+
             # Force-recompute potential dtype casts from all_gather
             if (
                 ag_node.all_input_nodes[0].op == "call_function"

torchtitan/models/deepseek_v3/__init__.py

@@ -97,8 +97,6 @@
         qk_rope_head_dim=64,
         v_head_dim=128,
         mscale=0.70,
-        attn_type="flex",
-        attn_mask_type="block_causal",
     ),
     "236B": DeepSeekV3ModelArgs(
         vocab_size=102400,