35 lines
1.2 KiB
Python
35 lines
1.2 KiB
Python
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#original code from https://github.com/genmoai/models under apache 2.0 license
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# Based on Llama3 Implementation.
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import torch
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def apply_rotary_emb_qk_real(
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xqk: torch.Tensor,
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freqs_cos: torch.Tensor,
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freqs_sin: torch.Tensor,
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) -> torch.Tensor:
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"""
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Apply rotary embeddings to input tensors using the given frequency tensor without complex numbers.
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Args:
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xqk (torch.Tensor): Query and/or Key tensors to apply rotary embeddings. Shape: (B, S, *, num_heads, D)
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Can be either just query or just key, or both stacked along some batch or * dim.
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freqs_cos (torch.Tensor): Precomputed cosine frequency tensor.
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freqs_sin (torch.Tensor): Precomputed sine frequency tensor.
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Returns:
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torch.Tensor: The input tensor with rotary embeddings applied.
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"""
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# Split the last dimension into even and odd parts
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xqk_even = xqk[..., 0::2]
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xqk_odd = xqk[..., 1::2]
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# Apply rotation
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cos_part = (xqk_even * freqs_cos - xqk_odd * freqs_sin).type_as(xqk)
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sin_part = (xqk_even * freqs_sin + xqk_odd * freqs_cos).type_as(xqk)
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# Interleave the results back into the original shape
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out = torch.stack([cos_part, sin_part], dim=-1).flatten(-2)
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return out
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