First commit

vllm/model_executor/layers/fused_moe/moe_pallas.py

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+import torch
+import torch.nn.functional as F
+from torch_xla.experimental.custom_kernel import _histogram
+
+
+def fused_moe(
+    hidden_states: torch.Tensor,
+    w1: torch.Tensor,
+    w2: torch.Tensor,
+    gating_output: torch.Tensor,
+    topk: int,
+    renormalize: bool,
+) -> torch.Tensor:
+    """
+    Args:
+        hidden_states: [*, hidden_size]
+        w1: [num_experts, intermediate_size * 2, hidden_size]
+        w2: [num_experts, hidden_size, intermediate_size]
+        gating_output: [*, num_experts]
+    """
+    orig_shape = hidden_states.shape
+    hidden_size = hidden_states.shape[-1]
+    num_tokens = hidden_states.shape[:-1].numel()
+    num_experts = w1.shape[0]
+    intermediate_size = w2.shape[-1]
+    device = hidden_states.device
+    dtype = hidden_states.dtype
+    assert (num_tokens * topk) % 16 == 0, (
+        "The Pallas GMM kernel requires num_tokens * topk to be a multiple of "
+        f"16 but got {num_tokens * topk}")
+
+    hidden_states = hidden_states.view(num_tokens, hidden_size)
+    gating_output = gating_output.view(num_tokens, num_experts)
+    topk_weights = gating_output.softmax(dim=-1, dtype=torch.float)
+    topk_weights, topk_indices = topk_weights.topk(topk, dim=-1)
+    if renormalize:
+        topk_weights = topk_weights / topk_weights.sum(dim=-1, keepdim=True)
+    topk_weights = topk_weights.to(dtype)
+
+    topk_indices = topk_indices.flatten()
+    topk_argsort_indices = topk_indices.argsort()
+    topk_argsort_revert_indices = topk_argsort_indices.argsort()
+    token_indices = torch.arange(num_tokens,
+                                 device=device).repeat_interleave(topk)
+    token_indices = token_indices[topk_argsort_indices]
+    group_sizes = _histogram(topk_indices.to(torch.int32), 0, num_experts - 1)
+
+    # NOTE(woosuk): The GMM Pallas kernel requires a different weight layout
+    # from HF Transformers.
+    w1 = w1.transpose(1, 2)
+    w2 = w2.transpose(1, 2)
+
+    x = hidden_states[token_indices]
+    x = torch.ops.xla.gmm(x, w1, group_sizes)
+    x = F.silu(x[..., :intermediate_size]) * x[..., intermediate_size:]
+    x = torch.ops.xla.gmm(x, w2, group_sizes)
+    x = x[topk_argsort_revert_indices].reshape(-1, topk, hidden_size)
+
+    x = x * topk_weights.unsqueeze_(dim=-1)
+    x = x.sum(dim=-2)
+    x = x.reshape(orig_shape)
+    return x