73 lines
2.3 KiB
C++
73 lines
2.3 KiB
C++
#pragma once
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// Tensor layout for Q/K/V tensors passed to attention kernels.
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// Internally, kernels always operate on BHLD [batch, n_heads, seq_len, head_dim].
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// When the caller passes BLHD, dims 1 and 2 are transposed at entry.
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enum TensorLayout : int {
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BHLD = 0, // [batch, n_heads, seq_len, head_dim]
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BLHD = 1, // [batch, seq_len, n_heads, head_dim]
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};
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// Unified attention params covering BOTH addressing modes:
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// - Contiguous K/V: dense [batch, kv_head, kv_len, head_dim] tensors (k/v).
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// - Paged (SGLang-style): flat pool [size, kv_head, head_dim] + req_to_token.
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// Each kernel selects the addressing via a KVSource policy (see
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// attn_layout_policies.cuh); a given call only touches the fields of one mode, so
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// this is a POD shared by both paths rather than two parallel structs that
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// drift out of sync.
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template<typename T, typename AT = float>
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struct AttentionParams {
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// Shape
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int batch;
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int q_head;
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int kv_head;
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int head_dim;
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int q_len; // Per-request in contiguous mode; total_q in paged mode.
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int kv_len; // Contiguous mode; paged mode uses kv_indptr.
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// Attention behavior
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float scale;
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// -1 = non-causal; >=0 = absolute position of first Q token
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int causal_offset;
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int use_mask;
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// pointers
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const T* __restrict__ q_ptr;
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const T* __restrict__ k_ptr;
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const T* __restrict__ v_ptr;
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T* __restrict__ o_ptr;
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const bool* __restrict__ mask;
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// strides
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int q_b_stride;
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int q_h_stride;
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int q_l_stride;
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int q_d_stride;
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int kv_b_stride;
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int kv_h_stride;
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int kv_l_stride;
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int kv_d_stride;
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int mask_b_stride;
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int mask_h_stride;
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int mask_l_stride;
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// Paged K/V addressing
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const int* __restrict__ req_to_token; // [num_reqs, max_context_len]
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const int* __restrict__ req_pool_indices; // [batch]
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const int* __restrict__ kv_indptr; // [batch + 1]
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const int* __restrict__ qo_indptr; // [batch + 1] or nullptr for decode
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const int* __restrict__ q_tile_to_batch; // [num_q_tiles], prefill only
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const int* __restrict__ q_tile_to_index; // [num_q_tiles], prefill only
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int num_q_tiles;
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int max_context_len; // req_to_token stride (dim 1)
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// Decode split-KV workspace
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int num_splits;
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AT* __restrict__ o_part;
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AT* __restrict__ ml_part;
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};
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