"""Fused MoE kernel.""" import torch import triton import triton.language as tl from vllm._C import ops @triton.jit def fused_moe_kernel( # Pointers to matrices a_ptr, b_ptr, c_ptr, topk_weights_ptr, sorted_token_ids_ptr, expert_ids_ptr, num_tokens_post_padded_ptr, # Matrix dimensions N, K, EM, num_valid_tokens, # The stride variables represent how much to increase the ptr by when moving by 1 # element in a particular dimension. E.g. `stride_am` is how much to increase `a_ptr` # by to get the element one row down (A has M rows). stride_am, stride_ak, stride_be, stride_bk, stride_bn, stride_cm, stride_cn, # Meta-parameters BLOCK_SIZE_M: tl.constexpr, BLOCK_SIZE_N: tl.constexpr, BLOCK_SIZE_K: tl.constexpr, GROUP_SIZE_M: tl.constexpr, MUL_ROUTED_WEIGHT: tl.constexpr, top_k: tl.constexpr, compute_type: tl.constexpr, ): """ Implements the fused computation for a Mixture of Experts (MOE) using token and expert matrices. Key Parameters: - A: The input tensor representing tokens with shape (*, K), where '*' can be any shape representing batches and K is the feature dimension of each token. - B: The stacked MOE weight tensor with shape (E, N, K), where E is the number of experts, K is the input feature dimension, and N is the output feature dimension. - C: The output cache tensor with shape (M, topk, N), where M is the total number of tokens post padding, topk is the number of times each token is repeated, and N is the output feature dimension. - sorted_token_ids: A tensor containing the sorted indices of tokens, repeated topk times and arranged by the expert index they are assigned to. - expert_ids: A tensor containing the indices of the expert for each block. It determines which expert matrix from B should be used for each block in A. This kernel performs the multiplication of a token by its corresponding expert matrix as determined by `expert_ids`. The sorting of `sorted_token_ids` by expert index and padding ensures divisibility by BLOCK_SIZE_M, which is necessary to maintain consistency in block matrix multiplication across different blocks processed by the same expert. """ # ----------------------------------------------------------- # Map program ids `pid` to the block of C it should compute. # This is done in a grouped ordering to promote L2 data reuse. pid = tl.program_id(axis=0) num_pid_m = tl.cdiv(EM, BLOCK_SIZE_M) num_pid_n = tl.cdiv(N, BLOCK_SIZE_N) num_pid_in_group = GROUP_SIZE_M * num_pid_n group_id = pid // num_pid_in_group first_pid_m = group_id * GROUP_SIZE_M group_size_m = min(num_pid_m - first_pid_m, GROUP_SIZE_M) pid_m = first_pid_m + ((pid % num_pid_in_group) % group_size_m) pid_n = (pid % num_pid_in_group) // group_size_m # ---------------------------------------------------------- # Create pointers for the first blocks of A and B. # We will advance this pointer as we move in the K direction # and accumulate # `a_ptrs` is a block of [BLOCK_SIZE_M, BLOCK_SIZE_K] pointers # `b_ptrs` is a block of [BLOCK_SIZE_K, BLOCK_SIZE_N] pointers num_tokens_post_padded = tl.load(num_tokens_post_padded_ptr) if pid_m * BLOCK_SIZE_M >= num_tokens_post_padded: return offs_token_id = pid_m * BLOCK_SIZE_M + tl.arange(0, BLOCK_SIZE_M) offs_token = tl.load(sorted_token_ids_ptr + offs_token_id) token_mask = offs_token < num_valid_tokens offs_bn = (pid_n * BLOCK_SIZE_N + tl.arange(0, BLOCK_SIZE_N)) % N offs_k = tl.arange(0, BLOCK_SIZE_K) a_ptrs = a_ptr + (offs_token[:, None] // top_k * stride_am + offs_k[None, :] * stride_ak) off_experts = tl.load(expert_ids_ptr + pid_m) b_ptrs = b_ptr + off_experts * stride_be + (offs_k[:, None] * stride_bk + offs_bn[None, :] * stride_bn) # ----------------------------------------------------------- # Iterate to compute a block of the C matrix. # We accumulate into a `[BLOCK_SIZE_M, BLOCK_SIZE_N]` block # of fp32 values for higher accuracy. # `accumulator` will be converted back to fp16 after the loop. accumulator = tl.zeros((BLOCK_SIZE_M, BLOCK_SIZE_N), dtype=tl.float32) for k in range(0, tl.cdiv(K, BLOCK_SIZE_K)): # Load the next block of A and B, generate a mask by checking the K dimension. a = tl.load(a_ptrs, mask=token_mask[:, None] & (offs_k[None, :] < K - k * BLOCK_SIZE_K), other=0.0) b = tl.load(b_ptrs, mask=offs_k[:, None] < K - k * BLOCK_SIZE_K, other=0.0) # We accumulate along the K dimension. accumulator += tl.dot(a, b) # Advance the ptrs to the next K block. a_ptrs += BLOCK_SIZE_K * stride_ak b_ptrs += BLOCK_SIZE_K * stride_bk if MUL_ROUTED_WEIGHT: moe_weight = tl.load(topk_weights_ptr + offs_token, mask=token_mask, other=0) accumulator = accumulator * moe_weight[:, None] accumulator = accumulator.to(compute_type) # ----------------------------------------------------------- # Write back the block of the output offs_cn = pid_n * BLOCK_SIZE_N + tl.arange(0, BLOCK_SIZE_N) c_ptrs = c_ptr + stride_cm * offs_token[:, None] + stride_cn * offs_cn[ None, :] c_mask = token_mask[:, None] & (offs_cn[None, :] < N) tl.store(c_ptrs, accumulator, mask=c_mask) def moe_align_block_size( topk_ids: torch.Tensor, block_size: int, num_experts: int) -> (torch.Tensor, torch.Tensor, torch.Tensor): """ Aligns the token distribution across experts to be compatible with block size for matrix multiplication. Parameters: - topk_ids: A tensor of shape [total_tokens, top_k] representing the top-k expert indices for each token. - block_size: The block size used in block matrix multiplication. - num_experts: The total number of experts. Returns: - sorted_token_ids: A tensor containing the sorted token indices according to their allocated expert. - expert_ids: A tensor indicating the assigned expert index for each block. - num_tokens_post_padded: The total number of tokens after padding, ensuring divisibility by block_size. This function pads the number of tokens that each expert needs to process so that it is divisible by block_size. Padding ensures that during block matrix multiplication, the dimensions align correctly. Example: Given topk_ids = [[2, 3, 4], [1, 2, 4], [1, 3, 4], [1, 2, 3]], block_size = 4, and num_experts = 4: - We initially have 12 tokens (after repeating 'top_k' times) and 4 experts, with each expert needing to process 3 tokens. - As block_size is 4, we pad 1 token for each expert. - First, flatten topk_ids to [2, 3, 4, 1, 2, 4, 1, 3, 4, 1, 2, 3]. - Then append padding tokens [12, 12, 12, 12] for each block. - After sorting by expert index, we obtain token_ids [3, 6, 9, 12, 0, 4, 10, 12, 1, 7, 11, 12, 2, 5, 8, 12]. Tokens 12 are non-existent (padding) and are ignored in the subsequent matrix multiplication. - The padding ensures that the total number of tokens is now divisible by block_size for proper block matrix operations. """ sorted_ids = torch.empty( (topk_ids.numel() + num_experts * (block_size - 1), ), dtype=torch.int32, device=topk_ids.device) expert_ids = torch.empty((topk_ids.numel() + num_experts, ), dtype=torch.int32, device=topk_ids.device) sorted_ids.fill_(topk_ids.numel()) num_tokens_post_pad = torch.empty((1), dtype=torch.int32, device=topk_ids.device) ops.moe_align_block_size(topk_ids, num_experts, block_size, sorted_ids, expert_ids, num_tokens_post_pad) return sorted_ids, expert_ids, num_tokens_post_pad def invoke_fused_moe_kernel(A: torch.Tensor, B: torch.Tensor, C: torch.Tensor, topk_weights: torch.Tensor, topk_ids: torch.Tensor, sorted_token_ids: torch.Tensor, expert_ids: torch.Tensor, num_tokens_post_padded: torch.Tensor, mul_routed_weight: bool, top_k: int, config: dict): assert topk_weights.stride(1) == 1 assert sorted_token_ids.stride(0) == 1 grid = lambda META: (triton.cdiv(sorted_token_ids.shape[0], META[ 'BLOCK_SIZE_M']) * triton.cdiv(B.shape[1], META['BLOCK_SIZE_N']), ) fused_moe_kernel[grid]( A, B, C, topk_weights, sorted_token_ids, expert_ids, num_tokens_post_padded, B.shape[1], B.shape[2], sorted_token_ids.shape[0], topk_ids.numel(), A.stride(0), A.stride(1), B.stride(0), B.stride(2), B.stride(1), C.stride(1), C.stride(2), MUL_ROUTED_WEIGHT=mul_routed_weight, top_k=top_k, compute_type=tl.bfloat16 if A.dtype == torch.bfloat16 else tl.float16, **config, ) def fused_moe(hidden_states: torch.Tensor, w1: torch.Tensor, w2: torch.Tensor, topk_weights: torch.Tensor, topk_ids: torch.Tensor, inplace=False): """ This function computes a Mixture of Experts (MoE) layer using two sets of weights, w1 and w2, and top-k gating mechanism. Parameters: - hidden_states (torch.Tensor): The input tensor to the MoE layer. - w1 (torch.Tensor): The first set of expert weights. - w2 (torch.Tensor): The second set of expert weights. - topk_weights (torch.Tensor): The weights for the top-k selected experts. - topk_ids (torch.Tensor): The indices of the top-k selected experts. - inplace (bool): If True, perform the operation in-place. Defaults to False. Returns: - torch.Tensor: The output tensor after applying the MoE layer. """ # Check constraints. assert hidden_states.shape[1] == w1.shape[2], "Incompatible dimensions" assert hidden_states.is_contiguous(), "Hidden_states must be contiguous" assert w1.is_contiguous(), "Expert weights1 must be contiguous" assert w2.is_contiguous(), "Expert weights2 must be contiguous" assert hidden_states.dtype in [ torch.float32, torch.float16, torch.bfloat16 ] M, _ = hidden_states.shape E, N, _ = w1.shape config = { 'BLOCK_SIZE_M': 64, 'BLOCK_SIZE_N': 64, 'BLOCK_SIZE_K': 32, 'GROUP_SIZE_M': 8 } if topk_ids.numel() <= w1.shape[0]: config = { 'BLOCK_SIZE_M': 16, 'BLOCK_SIZE_N': 32, 'BLOCK_SIZE_K': 64, 'GROUP_SIZE_M': 1 } intermediate_cache1 = torch.empty((M, topk_ids.shape[1], N), device=hidden_states.device, dtype=hidden_states.dtype) intermediate_cache2 = torch.empty((M * topk_ids.shape[1], N // 2), device=hidden_states.device, dtype=hidden_states.dtype) intermediate_cache3 = torch.empty((M, topk_ids.shape[1], w2.shape[1]), device=hidden_states.device, dtype=hidden_states.dtype) sorted_token_ids, expert_ids, num_tokens_post_padded = moe_align_block_size( topk_ids, config['BLOCK_SIZE_M'], E) invoke_fused_moe_kernel(hidden_states, w1, intermediate_cache1, topk_weights, topk_ids, sorted_token_ids, expert_ids, num_tokens_post_padded, False, topk_ids.shape[1], config) ops.silu_and_mul(intermediate_cache2, intermediate_cache1.view(-1, N)) invoke_fused_moe_kernel(intermediate_cache2, w2, intermediate_cache3, topk_weights, topk_ids, sorted_token_ids, expert_ids, num_tokens_post_padded, True, 1, config) if inplace: return torch.sum(intermediate_cache3.view(*intermediate_cache3.shape), dim=1, out=hidden_states) return torch.sum(intermediate_cache3.view(*intermediate_cache3.shape), dim=1)