107 lines
3.7 KiB
Python
107 lines
3.7 KiB
Python
# SPDX-License-Identifier: Apache-2.0
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# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
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import torch
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def mhc_pre_torch(
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residual: torch.Tensor,
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fn: torch.Tensor,
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hc_scale: torch.Tensor,
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hc_base: torch.Tensor,
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rms_eps: float,
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hc_pre_eps: float,
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hc_sinkhorn_eps: float,
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hc_post_mult_value: float,
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sinkhorn_repeat: int,
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n_splits: int = 1,
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) -> tuple[torch.Tensor, torch.Tensor, torch.Tensor]:
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"""
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Forward pass for mHC pre block.
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Args:
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residual: shape (..., hc_mult, hidden_size), dtype torch.bfloat16
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fn: shape (hc_mult3, hc_mult * hidden_size), dtype torch.float32
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hc_scale: shape (3,), dtype torch.float32
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hc_base: shape (hc_mult3,), dtype torch.float32
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rms_eps: RMS normalization epsilon
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hc_pre_eps: pre-mix epsilon
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hc_sinkhorn_eps: sinkhorn epsilon
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hc_post_mult_value: post-mix multiplier value
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sinkhorn_repeat: number of sinkhorn iterations
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n_splits: split-k factor;
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Returns:
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post_mix: shape (..., hc_mult), dtype torch.float32
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comb_mix: shape (..., hc_mult, hc_mult), dtype torch.float32
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layer_input: shape (..., hidden_size), dtype torch.bfloat16
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"""
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# Validate shapes
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assert residual.dtype == torch.bfloat16
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assert fn.dtype == torch.float32
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assert hc_scale.dtype == torch.float32
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assert hc_base.dtype == torch.float32
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hc_mult = residual.shape[-2]
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hidden_size = residual.shape[-1]
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hc_mult2 = hc_mult * hc_mult
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hc_mult3 = hc_mult * 2 + hc_mult2
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hc_hidden_size = hc_mult * hidden_size
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assert fn.shape[0] == hc_mult3
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assert fn.shape[1] == hc_hidden_size
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assert hc_scale.shape == (3,)
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assert hc_base.shape == (hc_mult3,)
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outer_shape = residual.shape[:-2]
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residual_flat = residual.view(-1, hc_mult, hidden_size)
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num_tokens = residual_flat.shape[0]
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fn_flat = fn
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x = residual_flat.view(num_tokens, hc_mult * hidden_size).to(torch.float32)
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mixes = torch.matmul(x, fn_flat.t())
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sqrsum = x.square().sum(dim=-1, keepdim=True)
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mixes = mixes * torch.rsqrt(sqrsum / (hc_mult * hidden_size) + rms_eps)
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pre_logits = mixes[:, :hc_mult] * hc_scale[0] + hc_base[:hc_mult]
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pre_mix = torch.sigmoid(pre_logits) + hc_pre_eps
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post_logits = (
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mixes[:, hc_mult : 2 * hc_mult] * hc_scale[1] + hc_base[hc_mult : 2 * hc_mult]
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)
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post_mix = torch.sigmoid(post_logits) * hc_post_mult_value
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comb_logits = mixes[:, 2 * hc_mult :].view(num_tokens, hc_mult, hc_mult) * hc_scale[
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2
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] + hc_base[2 * hc_mult :].view(1, hc_mult, hc_mult)
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comb_mix = torch.softmax(comb_logits, dim=-1) + hc_sinkhorn_eps
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comb_mix = comb_mix / (comb_mix.sum(dim=-2, keepdim=True) + hc_sinkhorn_eps)
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for _ in range(sinkhorn_repeat - 1):
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comb_mix = comb_mix / (comb_mix.sum(dim=-1, keepdim=True) + hc_sinkhorn_eps)
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comb_mix = comb_mix / (comb_mix.sum(dim=-2, keepdim=True) + hc_sinkhorn_eps)
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layer_input = torch.sum(
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pre_mix.unsqueeze(-1) * residual_flat.to(torch.float32), dim=1
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).to(torch.bfloat16)
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return (
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post_mix.view(*outer_shape, hc_mult, 1),
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comb_mix.view(*outer_shape, hc_mult, hc_mult),
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layer_input.view(*outer_shape, hidden_size),
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)
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def mhc_post_torch(
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x: torch.Tensor,
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residual: torch.Tensor,
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post_layer_mix: torch.Tensor,
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comb_res_mix: torch.Tensor,
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) -> torch.Tensor:
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mixed_residual = torch.einsum(
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"...ij,...ih->...jh",
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comb_res_mix.to(torch.float32),
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residual.to(torch.float32),
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)
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post_term = post_layer_mix.to(torch.float32) * x.unsqueeze(-2).to(torch.float32)
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return (mixed_residual + post_term).to(residual.dtype)
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