forked from ccf-ai-infra/TileOPs-Metax
66 lines
1.9 KiB
Python
66 lines
1.9 KiB
Python
"""ALiBi position-encoding generative op."""
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from typing import Dict, Optional
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import torch
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from tileops.kernels.elementwise import AlibiFwdKernel
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from tileops.kernels.kernel_base import Kernel
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from ..op_base import Op
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from ._base import _OP_REGISTRY, _apply_fp8_post_cast
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class AlibiFwdOp(Op):
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"""ALiBi position encoding: bias[h, i, j] = -slope_h * |i - j|.
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Generates the full (num_heads, seq_len, seq_len) bias tensor.
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Args:
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seq_len: Sequence length.
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num_heads: Number of attention heads.
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dtype: Torch dtype.
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kernel_map: Optional dispatch override mapping kernel keys to
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``Kernel`` subclasses. Falls back to ``default_kernel_map``.
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"""
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_op_name = "alibi"
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_wrapped = None
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def __init__(
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self,
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seq_len: int,
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num_heads: int,
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dtype: torch.dtype,
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*,
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kernel_map: Optional[Dict[str, Kernel]] = None,
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):
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self.seq_len = seq_len
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self.num_heads = num_heads
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self.dtype = dtype
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self.dispatch_kernel(kernel_map)
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self.kernel = self.kernel_map[self._op_name](seq_len, num_heads, dtype)
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# Scalar tensor used as device/dtype carrier for torch.compile tracing
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self._device_carrier = torch.empty((), dtype=dtype, device="cuda")
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self._instance_key = id(self)
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_OP_REGISTRY[self._instance_key] = self
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@property
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def default_kernel_map(self):
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return {"alibi": AlibiFwdKernel}
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def _eager_forward(self) -> torch.Tensor:
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out = self.kernel()
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result = out.reshape(self.num_heads, self.seq_len, self.seq_len)
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return _apply_fp8_post_cast(result, self.kernel)
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def forward(self) -> torch.Tensor:
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wrapped = type(self)._wrapped
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if wrapped is not None:
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return wrapped(
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self._device_carrier,
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self.num_heads, self.seq_len,
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self._instance_key,
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)
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return self._eager_forward()
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