Add Tensor Parallel to torch_native_llama (#1876)

python/sglang/srt/model_parallel.py

@@ -0,0 +1,98 @@
+"""
+Common utilities for torch model parallelism.
+"""
+
+from typing import Optional, Sequence
+
+import torch
+from torch.distributed.device_mesh import DeviceMesh
+
+try:
+    from torch.distributed.tensor import DTensor, Shard
+except ImportError:
+    # torch 2.4 or older
+    from torch.distributed._tensor import DTensor, Shard
+
+from torch.distributed._functional_collectives import AsyncCollectiveTensor
+from torch.distributed.tensor.parallel import (
+    ColwiseParallel,
+    RowwiseParallel,
+    parallelize_module,
+)
+
+
+class ColwiseParallelSharded(ColwiseParallel):
+    """
+    A version of ColwiseParallel where the local weight has been already
+    sharded.  This is used for the fused wqkv case, where during loading, we
+    already sharded wq, wk, wv before fusing them.
+    """
+
+    # Override the _partition_linear_fn in ColwiseParallel
+    def _partition_linear_fn(self, name, module, device_mesh):
+        # colwise shard weight/bias to Shard(0), weight be Shard(0)
+        # means Colwise as Linear is input * weight^T + bias, where
+        # weight would become Shard(1)
+        for name, param in module.named_parameters():
+            dtensor = DTensor.from_local(param, device_mesh, [Shard(0)])
+            dist_param = torch.nn.Parameter(dtensor, requires_grad=False)
+            module.register_parameter(name, dist_param)
+
+
+class RowwiseParallelMaybeWait(RowwiseParallel):
+    """
+    A version of RowwiseParallel that waits for the output (establish dependency
+    between comm stream and compute stream in CUDA sense) before going into the
+    next op. This is needed to workaround the current interaction between
+    AsyncCollectiveTensor and custom ops, such as `class RMSNorm(CustomOp)`.
+    """
+
+    @staticmethod
+    def _prepare_output_fn(output_layouts, use_local_output, mod, outputs, device_mesh):
+        outputs = super(
+            RowwiseParallelMaybeWait, RowwiseParallelMaybeWait
+        )._prepare_output_fn(
+            output_layouts, use_local_output, mod, outputs, device_mesh
+        )
+        # wait for the output to be ready
+        if isinstance(outputs, AsyncCollectiveTensor):
+            return outputs.wait()
+        else:
+            return outputs
+
+
+def tensor_parallel(
+    module: torch.nn.Module,
+    device_mesh: Optional[DeviceMesh] = None,
+):
+    """
+    Tensor parallelize the model across the given device mesh.
+    Args:
+        module (`torch.nn.Module`):
+            The module to tensor parallelize.
+        device_mesh (`torch.distributed.DeviceMesh`):
+            The device mesh to use for tensor parallelism.
+    """
+
+    # Tensor parallelize a nn.Module based on the `_tp_plan` attribute of the module.
+    # No op if `_tp_plan` attribute does not exist under the module.
+    # This is a helper function to be used with `model.apply` to recursively
+    # parallelize a model.
+    def tplize(mod: torch.nn.Module) -> None:
+        tp_plan = getattr(mod, "_tp_plan", None)
+        if tp_plan is None:
+            return
+        for child_name, tp_style in tp_plan.items():
+            submod = mod.get_submodule(child_name)
+            if tp_style == "Colwise":
+                parallelize_module(submod, device_mesh, ColwiseParallel())
+            elif tp_style == "Rowwise":
+                parallelize_module(submod, device_mesh, RowwiseParallelMaybeWait())
+            elif tp_style == "Colwise_Sharded":
+                parallelize_module(submod, device_mesh, ColwiseParallelSharded())
+            else:
+                raise ValueError(f"Unknown TP style {tp_style}")
+
+    # `apply` is a native method of `nn.Module` that recursively applies a
+    # function to every submodule.
+    module.apply(tplize)