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https://github.com/tinygrad/tinygrad.git
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353 lines
16 KiB
Python
353 lines
16 KiB
Python
import math
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from tinygrad import Tensor, dtypes
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from tinygrad.uop.ops import UOp
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from extra.thunder.tiny.tk import WARP_THREADS
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from extra.thunder.tiny.tk.kernel import Kernel
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from extra.thunder.tiny.tk.tiles import GL, TileLayout
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NUM_WORKERS = 1
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Q_BLOCK_SIZE = 16
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KV_BLOCK_SIZE = 16
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def flash_attention(xq, xk, xv, attn_mask:Tensor|None=None, is_causal:bool=False):
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if len(xq.shape) == 3: xq, xk, xv = xq.unsqueeze(0), xk.unsqueeze(0), xv.unsqueeze(0)
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odtype = xq.dtype
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xq, xk, xv = xq.transpose(1, 2).cast(dtypes.bfloat16), xk.transpose(1, 2).cast(dtypes.bfloat16), xv.transpose(1, 2).cast(dtypes.bfloat16)
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_, N_, _, D_ = xq.shape
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block_size = max(Q_BLOCK_SIZE, KV_BLOCK_SIZE)
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assert D_ % block_size == 0, f"embedding dimension must be multiple of block size, got {D_=} {block_size=}"
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# pad to multiple of block size
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xq = xq.pad(((0, 0), (0, (block_size - (xq.shape[1] % block_size)) % block_size), (0, 0), (0, 0)))
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xk = xk.pad(((0, 0), (0, (block_size - (xk.shape[1] % block_size)) % block_size), (0, 0), (0, 0)))
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xv = xv.pad(((0, 0), (0, (block_size - (xv.shape[1] % block_size)) % block_size), (0, 0), (0, 0)))
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B, N, H, D = xq.shape
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H_KV = xk.shape[2]
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GROUP_SIZE = H // H_KV
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print(f"Flash Attention {B=} {N=} {H=} {D=} {H_KV=} {GROUP_SIZE=}")
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def custom_forward(ou:UOp, l_vecu:UOp, qu:UOp, ku:UOp, vu:UOp, masku:UOp) -> UOp:
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with Kernel("fa_custom_forward", (H, N // (Q_BLOCK_SIZE*NUM_WORKERS), B), NUM_WORKERS * WARP_THREADS) as ker:
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warp = ker.warp
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o, q, k, v, mask, l_vec = GL(ou, ker), GL(qu, ker), GL(ku, ker), GL(vu, ker), GL(masku, ker), GL(l_vecu, ker)
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head = ker.blockIdx_x
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head_kv = head // GROUP_SIZE
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batch = ker.blockIdx_z
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q_seq = ker.blockIdx_y * NUM_WORKERS + ker.warpid
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k_smem = ker.st((KV_BLOCK_SIZE, D), dtypes.bfloat16)
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v_smem = ker.st((KV_BLOCK_SIZE, D), dtypes.bfloat16)
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q_reg_fl = ker.rt((Q_BLOCK_SIZE, D), dtypes.float32)
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q_reg = ker.rt((Q_BLOCK_SIZE, D), dtypes.bfloat16)
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q_reg_transposed = ker.rt((D, Q_BLOCK_SIZE), dtypes.bfloat16, TileLayout.COL)
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k_reg = ker.rt((KV_BLOCK_SIZE, D), dtypes.bfloat16)
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k_reg_transposed = ker.rt((D, KV_BLOCK_SIZE), dtypes.bfloat16, TileLayout.COL)
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v_reg = ker.rt((KV_BLOCK_SIZE, D), dtypes.bfloat16, TileLayout.COL)
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o_reg = ker.rt((D, Q_BLOCK_SIZE), dtypes.float32, TileLayout.COL)
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o_reg_transposed = ker.rt((Q_BLOCK_SIZE, D), dtypes.float32)
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att_block = ker.rt((KV_BLOCK_SIZE, Q_BLOCK_SIZE), dtypes.float32, TileLayout.COL)
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att_block_mma = ker.rt((KV_BLOCK_SIZE, Q_BLOCK_SIZE), dtypes.bfloat16, TileLayout.COL)
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mask_reg = ker.rt((Q_BLOCK_SIZE, KV_BLOCK_SIZE), dtypes.float32)
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mask_reg_transposed = ker.rt((KV_BLOCK_SIZE, Q_BLOCK_SIZE), dtypes.float32, TileLayout.COL)
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max_vec_last = ker.rv(KV_BLOCK_SIZE, dtypes.float32)
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max_vec = ker.rv(KV_BLOCK_SIZE, dtypes.float32)
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norm_vec = ker.rv(KV_BLOCK_SIZE, dtypes.float32)
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scale_vec = ker.rv(KV_BLOCK_SIZE, dtypes.float32)
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max_vec = warp.neg_inf(max_vec)
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norm_vec = warp.zero(norm_vec)
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o_reg = warp.zero(o_reg)
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scale_vec = warp.ones(scale_vec)
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# load q tile
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q_reg_fl = warp.load(q_reg_fl, q, (), (batch, q_seq, head, 0), axis=1)
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q_reg_fl *= (1.0 / math.sqrt(D)) * (1.0 / math.log(2))
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q_reg = warp.copy(q_reg, q_reg_fl)
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q_reg_transposed = warp.transpose(q_reg_transposed, q_reg)
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for kv_idx in ker.range(N // KV_BLOCK_SIZE):
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k_smem = warp.load(k_smem, k, (), (batch, kv_idx, head_kv, 0), axis=1)
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v_smem = warp.load(v_smem, v, (), (batch, kv_idx, head_kv, 0), axis=1)
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k_reg = warp.load(k_reg, k_smem)
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v_reg = warp.load(v_reg, v_smem)
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# mma qk^t
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att_block = warp.zero(att_block.after(kv_idx))
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k_reg_transposed = warp.transpose(k_reg_transposed, k_reg)
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att_block = warp.mma_AtB(att_block, k_reg_transposed, q_reg_transposed)
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# apply attention mask
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mask_reg = warp.load(mask_reg, mask, (), (batch, 0, q_seq, kv_idx), axis=2)
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mask_reg_transposed = warp.transpose(mask_reg_transposed, mask_reg)
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att_block += mask_reg_transposed
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# softmax
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max_vec_last = warp.copy(max_vec_last.after(kv_idx), max_vec)
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max_vec = warp.row_reduce(max_vec.after(max_vec_last), att_block, lambda a, b: a.maximum(b), init_value=-math.inf)
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scale_vec = warp.map(scale_vec.after(max_vec_last, max_vec), lambda _, idx: max_vec_last[*idx] - max_vec[*idx])
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scale_vec = scale_vec.exp2()
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o_reg *= scale_vec
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norm_vec *= scale_vec
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att_block -= max_vec
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att_block = att_block.exp2()
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norm_vec = warp.row_reduce(norm_vec.after(scale_vec), att_block, lambda a, b: a + b)
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# mma av
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att_block_mma = warp.copy(att_block_mma.after(kv_idx, norm_vec), att_block)
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o_reg = warp.mma_AtB(o_reg, v_reg, att_block_mma)
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o_reg = ker.endrange()
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norm_vec = norm_vec.after(o_reg)
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max_vec = max_vec.after(o_reg)
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o_reg /= norm_vec
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o_reg_transposed = warp.transpose(o_reg_transposed, o_reg)
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o = warp.store(o, o_reg_transposed, (batch, q_seq, head, 0), (), axis=1)
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norm_vec = norm_vec.after(o)
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max_vec = max_vec.after(o)
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max_vec *= math.log(2)
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norm_vec = norm_vec.log2() * math.log(2)
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norm_vec += max_vec
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l_vec = warp.store(l_vec, norm_vec, (batch, head, 0, q_seq), (), axis=2)
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o = o.after(l_vec)
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return ker.finish()
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def custom_backward_q(dqu:UOp, dou:UOp, qu:UOp, ku:UOp, vu:UOp, masku:UOp, l_vecu:UOp, delta_vecu:UOp) -> UOp:
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with Kernel("fa_custom_backward_q", (H, N // (Q_BLOCK_SIZE*NUM_WORKERS), B), NUM_WORKERS * WARP_THREADS) as ker:
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warp = ker.warp
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dq, do, q, k, v, mask = GL(dqu, ker), GL(dou, ker), GL(qu, ker), GL(ku, ker), GL(vu, ker), GL(masku, ker)
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l_vec, delta_vec = GL(l_vecu, ker), GL(delta_vecu, ker)
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head = ker.blockIdx_x
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head_kv = head // GROUP_SIZE
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batch = ker.blockIdx_z
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q_seq = ker.blockIdx_y * NUM_WORKERS + ker.warpid
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k_smem = ker.st((KV_BLOCK_SIZE, D), dtypes.bfloat16)
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v_smem = ker.st((KV_BLOCK_SIZE, D), dtypes.bfloat16)
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q_reg = ker.rt((Q_BLOCK_SIZE, D), dtypes.bfloat16)
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q_reg_t = ker.rt((D, Q_BLOCK_SIZE), dtypes.bfloat16, TileLayout.COL)
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k_reg = ker.rt((KV_BLOCK_SIZE, D), dtypes.bfloat16)
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k_reg_t = ker.rt((D, KV_BLOCK_SIZE), dtypes.bfloat16, TileLayout.COL)
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k_reg_col = ker.rt((KV_BLOCK_SIZE, D), dtypes.bfloat16, TileLayout.COL)
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k_reg_col_t = ker.rt((D, KV_BLOCK_SIZE), dtypes.bfloat16)
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v_reg = ker.rt((KV_BLOCK_SIZE, D), dtypes.bfloat16)
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mask_reg = ker.rt((Q_BLOCK_SIZE, KV_BLOCK_SIZE), dtypes.float32)
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mask_reg_transposed = ker.rt((KV_BLOCK_SIZE, Q_BLOCK_SIZE), dtypes.float32, TileLayout.COL)
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dq_reg = ker.rt((D, Q_BLOCK_SIZE), dtypes.float32, TileLayout.COL)
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dq_reg_transposed = ker.rt((Q_BLOCK_SIZE, D), dtypes.float32)
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do_reg = ker.rt((Q_BLOCK_SIZE, D), dtypes.bfloat16)
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dp_block = ker.rt((KV_BLOCK_SIZE, Q_BLOCK_SIZE), dtypes.float32, TileLayout.COL)
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att_block = ker.rt((KV_BLOCK_SIZE, Q_BLOCK_SIZE), dtypes.float32, TileLayout.COL)
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att_block_mma = ker.rt((KV_BLOCK_SIZE, Q_BLOCK_SIZE), dtypes.bfloat16, TileLayout.COL)
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l_vec_reg = ker.rv(Q_BLOCK_SIZE, dtypes.float32)
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delta_vec_reg = ker.rv(Q_BLOCK_SIZE, dtypes.float32)
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dq_reg = warp.zero(dq_reg)
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# load q tile
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q_reg = warp.load(q_reg, q, (), (batch, q_seq, head, 0), axis=1)
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q_reg_t = warp.transpose(q_reg_t, q_reg)
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# load do tile
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do_reg = warp.load(do_reg, do, (), (batch, q_seq, head, 0), axis=1)
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# load l_vec
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l_vec_reg = warp.load(l_vec_reg, l_vec, (), (batch, head, 0, q_seq), axis=2)
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l_vec_reg *= 1.0 / math.log(2)
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delta_vec_reg = warp.load(delta_vec_reg, delta_vec, (), (batch, head, 0, q_seq), axis=2)
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for kv_idx in ker.range(N // KV_BLOCK_SIZE):
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k_smem = warp.load(k_smem, k, (), (batch, kv_idx, head_kv, 0), axis=1)
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v_smem = warp.load(v_smem, v, (), (batch, kv_idx, head_kv, 0), axis=1)
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k_reg = warp.load(k_reg, k_smem)
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k_reg_t = warp.transpose(k_reg_t, k_reg)
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k_reg_col = warp.load(k_reg_col, k_smem)
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k_reg_col_t = warp.transpose(k_reg_col_t, k_reg_col)
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v_reg = warp.load(v_reg, v_smem)
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# mma qk^t
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att_block = warp.zero(att_block.after(kv_idx))
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att_block = warp.mma_AtB(att_block, k_reg_t, q_reg_t)
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# apply attention mask
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mask_reg = warp.load(mask_reg, mask, (), (batch, 0, q_seq, kv_idx), axis=2)
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mask_reg_transposed = warp.transpose(mask_reg_transposed, mask_reg)
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att_block += mask_reg_transposed
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att_block *= (1.0 / math.sqrt(D)) * (1.0 / math.log(2))
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att_block -= l_vec_reg
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att_block = att_block.exp2()
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dp_block = warp.zero(dp_block.after(kv_idx, att_block))
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dp_block = warp.mma_ABt(dp_block, v_reg, do_reg)
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dp_block -= delta_vec_reg
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att_block *= dp_block
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att_block_mma = warp.copy(att_block_mma.after(att_block), att_block)
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dq_reg = warp.mma_AB(dq_reg, k_reg_col_t, att_block_mma)
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dq_reg = ker.endrange()
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dq_reg *= 1.0 / math.sqrt(D)
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dq_reg_transposed = warp.transpose(dq_reg_transposed, dq_reg)
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dq = warp.store(dq, dq_reg_transposed, (batch, q_seq, head, 0), axis=1)
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return ker.finish()
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def custom_backward_kv(dku:UOp, dvu:UOp, dou:UOp, qu:UOp, ku:UOp, vu:UOp, masku:UOp, l_vecu:UOp, delta_vecu:UOp) -> UOp:
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with Kernel("fa_custom_backward_kv", (H_KV, N // (KV_BLOCK_SIZE*NUM_WORKERS), B), NUM_WORKERS * WARP_THREADS) as ker:
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warp = ker.warp
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dk, dv, do, q, k, v, mask = GL(dku, ker), GL(dvu, ker), GL(dou, ker), GL(qu, ker), GL(ku, ker), GL(vu, ker), GL(masku, ker)
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l_vec, delta_vec = GL(l_vecu, ker), GL(delta_vecu, ker)
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head_kv = ker.blockIdx_x
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batch = ker.blockIdx_z
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kv_seq = ker.blockIdx_y * NUM_WORKERS + ker.warpid
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q_smem = ker.st((Q_BLOCK_SIZE, D), dtypes.bfloat16)
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do_smem = ker.st((Q_BLOCK_SIZE, D), dtypes.bfloat16)
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att_smem = ker.st((Q_BLOCK_SIZE, KV_BLOCK_SIZE), dtypes.bfloat16)
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q_reg = ker.rt((Q_BLOCK_SIZE, D), dtypes.bfloat16)
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q_reg_t = ker.rt((D, Q_BLOCK_SIZE), dtypes.bfloat16, TileLayout.COL)
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q_reg_col = ker.rt((Q_BLOCK_SIZE, D), dtypes.bfloat16, TileLayout.COL)
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k_reg = ker.rt((KV_BLOCK_SIZE, D), dtypes.bfloat16)
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k_reg_t = ker.rt((D, KV_BLOCK_SIZE), dtypes.bfloat16, TileLayout.COL)
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v_reg = ker.rt((KV_BLOCK_SIZE, D), dtypes.bfloat16)
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mask_reg = ker.rt((Q_BLOCK_SIZE, KV_BLOCK_SIZE), dtypes.float32)
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mask_reg_transposed = ker.rt((KV_BLOCK_SIZE, Q_BLOCK_SIZE), dtypes.float32, TileLayout.COL)
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dk_reg = ker.rt((KV_BLOCK_SIZE, D), dtypes.float32, TileLayout.COL)
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dv_reg = ker.rt((KV_BLOCK_SIZE, D), dtypes.float32, TileLayout.COL)
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do_reg = ker.rt((Q_BLOCK_SIZE, D), dtypes.bfloat16)
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do_reg_col = ker.rt((Q_BLOCK_SIZE, D), dtypes.bfloat16, TileLayout.COL)
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dp_block = ker.rt((KV_BLOCK_SIZE, Q_BLOCK_SIZE), dtypes.float32, TileLayout.COL)
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att_block = ker.rt((KV_BLOCK_SIZE, Q_BLOCK_SIZE), dtypes.float32, TileLayout.COL)
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att_block_mma = ker.rt((KV_BLOCK_SIZE, Q_BLOCK_SIZE), dtypes.bfloat16, TileLayout.COL)
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att_block_transposed = ker.rt((Q_BLOCK_SIZE, KV_BLOCK_SIZE), dtypes.bfloat16, TileLayout.COL)
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att_block_row = ker.rt((Q_BLOCK_SIZE, KV_BLOCK_SIZE), dtypes.bfloat16)
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l_vec_reg = ker.rv(Q_BLOCK_SIZE, dtypes.float32)
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delta_vec_reg = ker.rv(Q_BLOCK_SIZE, dtypes.float32)
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dk_reg = warp.zero(dk_reg)
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dv_reg = warp.zero(dv_reg)
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# load kv tile
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k_reg = warp.load(k_reg, k, (), (batch, kv_seq, head_kv, 0), axis=1)
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k_reg_t = warp.transpose(k_reg_t, k_reg)
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v_reg = warp.load(v_reg, v, (), (batch, kv_seq, head_kv, 0), axis=1)
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for q_idx in ker.range(N // Q_BLOCK_SIZE):
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for g in ker.range(GROUP_SIZE):
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head_q = head_kv * GROUP_SIZE + g
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# load q and do
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q_smem = warp.load(q_smem, q, (), (batch, q_idx, head_q, 0), axis=1)
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do_smem = warp.load(do_smem, do, (), (batch, q_idx, head_q, 0), axis=1)
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q_reg = warp.load(q_reg, q_smem)
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q_reg_t = warp.transpose(q_reg_t, q_reg)
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q_reg_col = warp.load(q_reg_col, q_smem)
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do_reg = warp.load(do_reg, do_smem)
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do_reg_col = warp.load(do_reg_col, do_smem)
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# load l_vec and delta_vec
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l_vec_reg = warp.load(l_vec_reg, l_vec, (), (batch, head_q, 0, q_idx), axis=2)
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l_vec_reg *= 1.0 / math.log(2)
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delta_vec_reg = warp.load(delta_vec_reg, delta_vec, (), (batch, head_q, 0, q_idx), axis=2)
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# mma qk^t
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att_block = warp.zero(att_block.after(g))
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att_block = warp.mma_AtB(att_block, k_reg_t, q_reg_t)
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# apply attention mask
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mask_reg = warp.load(mask_reg, mask, (), (batch, 0, q_idx, kv_seq), axis=2)
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mask_reg_transposed = warp.transpose(mask_reg_transposed, mask_reg)
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att_block += mask_reg_transposed
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att_block *= (1.0 / math.sqrt(D)) * (1.0 / math.log(2))
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att_block -= l_vec_reg
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att_block = att_block.exp2()
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att_block_mma = warp.copy(att_block_mma, att_block)
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att_block_transposed = warp.transpose(att_block_transposed, att_block_mma)
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att_smem = warp.store(att_smem, att_block_transposed)
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att_block_row = warp.load(att_block_row, att_smem)
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dv_reg_ = warp.mma_AB(dv_reg, att_block_row, do_reg_col)
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dp_block = warp.zero(dp_block.after(g, q_idx, dv_reg_))
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dp_block = warp.mma_ABt(dp_block, v_reg, do_reg)
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dp_block -= delta_vec_reg
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att_block *= dp_block
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att_block_mma = warp.copy(att_block_mma, att_block)
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att_block_transposed = warp.transpose(att_block_transposed, att_block_mma)
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att_smem = warp.store(att_smem, att_block_transposed)
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att_block_row = warp.load(att_block_row, att_smem)
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dk_reg = warp.mma_AB(dk_reg, att_block_row, q_reg_col)
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dk_reg = ker.endrange(2)
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dv_reg = dv_reg.after(dk_reg)
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dk_reg *= 1.0 / math.sqrt(D)
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dk = warp.store(dk, dk_reg, (batch, kv_seq, head_kv, 0), axis=1)
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dv = warp.store(dv, dv_reg, (batch, kv_seq, head_kv, 0), axis=1)
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return ker.finish(2)
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if is_causal:
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if attn_mask is not None: raise RuntimeError("cannot set attn_mask when is_causal=True")
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attn_mask = Tensor.ones((B, 1, N, N), requires_grad=False, device=xq.device, dtype=dtypes.bool).tril()
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if attn_mask is not None:
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if attn_mask.dtype == dtypes.bool: attn_mask = attn_mask.where(0, -float("inf"))
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else:
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attn_mask = Tensor.zeros((B, 1, N, N), requires_grad=False, device=xq.device, dtype=dtypes.float32)
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attn = Tensor.empty_like(xq)
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l_vec = Tensor.empty(B, H, 1, N, requires_grad=False, device=xq.device, dtype=dtypes.float32).detach()
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def grad(gradu:UOp, kernel:UOp) -> tuple[None, None, UOp, UOp, UOp, None]:
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grad = Tensor(gradu)
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grad_q = Tensor.empty_like(q := Tensor(kernel.src[2]))
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grad_k = Tensor.empty_like(k := Tensor(kernel.src[3]))
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grad_v = Tensor.empty_like(v := Tensor(kernel.src[4]))
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mask = Tensor(kernel.src[5])
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delta_vec = (grad * attn).sum(-1).transpose(1, 2).unsqueeze(-2).detach()
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print(l_vec.shape, delta_vec.shape, grad.shape, attn.shape, grad_q.shape, grad_k.shape, grad_v.shape)
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grad_q = Tensor.custom_kernel(grad_q, grad, q, k, v, mask, l_vec, delta_vec, fxn=custom_backward_q)[0]
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grad_k, grad_v = Tensor.custom_kernel(grad_k, grad_v, grad, q, k, v, mask, l_vec, delta_vec, fxn=custom_backward_kv)[:2]
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return (None, None, grad_q.uop, grad_k.uop, grad_v.uop, None)
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attn, l_vec = Tensor.custom_kernel(attn, l_vec, xq, xk, xv, attn_mask, fxn=custom_forward, grad_fxn=grad)[:2]
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attn = attn[:, :N_, :, :D_]
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return attn.transpose(1, 2).cast(odtype)
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