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| 1 | +use candle_core::{IndexOp, Result, Tensor}; |
| 2 | +use candle_nn::{ |
| 3 | + layer_norm, linear_no_bias, LayerNorm, LayerNormConfig, Linear, Module, VarBuilder, |
| 4 | +}; |
| 5 | + |
| 6 | +use crate::attend::Attend; |
| 7 | + |
| 8 | +#[derive(Debug)] |
| 9 | +pub struct ToQKV { |
| 10 | + pub(crate) linear: Linear, |
| 11 | + pub(crate) heads: usize, |
| 12 | +} |
| 13 | + |
| 14 | +impl ToQKV { |
| 15 | + pub fn new(vb: VarBuilder, dim: usize, hidden_size: usize, heads: usize) -> Result<Self> { |
| 16 | + Ok(Self { |
| 17 | + linear: linear_no_bias(dim, hidden_size * 3, vb)?, |
| 18 | + heads, |
| 19 | + }) |
| 20 | + } |
| 21 | + |
| 22 | + pub fn rearrange(&self, xs: &Tensor) -> Result<(Tensor, Tensor, Tensor)> { |
| 23 | + let xs_dims = xs.dims(); |
| 24 | + let (h, qkv) = (self.heads, 3); |
| 25 | + let b = xs_dims[0]; |
| 26 | + let n = xs_dims[1]; |
| 27 | + let total_dim = xs_dims[2]; |
| 28 | + let dim_head = total_dim / (qkv * h); |
| 29 | + let xs = xs.reshape((b, n, qkv, h, dim_head))?; |
| 30 | + let xs = xs.permute((2, 0, 3, 1, 4))?; |
| 31 | + |
| 32 | + let q = xs.i(0)?; |
| 33 | + let k = xs.i(1)?; |
| 34 | + let v = xs.i(2)?; |
| 35 | + |
| 36 | + Ok((q, k, v)) |
| 37 | + } |
| 38 | + |
| 39 | + pub fn forward(&self, xs: &Tensor) -> Result<(Tensor, Tensor, Tensor)> { |
| 40 | + let xs = self.linear.forward(xs)?; |
| 41 | + self.rearrange(&xs) |
| 42 | + } |
| 43 | +} |
| 44 | + |
| 45 | +#[derive(Debug)] |
| 46 | +pub struct ToValueResidualMix { |
| 47 | + pub(crate) linear: Linear, |
| 48 | +} |
| 49 | + |
| 50 | +impl ToValueResidualMix { |
| 51 | + pub fn new(vb: VarBuilder, dim: usize, heads: usize) -> Result<Self> { |
| 52 | + Ok(Self { |
| 53 | + linear: linear_no_bias(dim, heads, vb)?, |
| 54 | + }) |
| 55 | + } |
| 56 | + |
| 57 | + pub fn rearrange(&self, xs: &Tensor) -> Result<Tensor> { |
| 58 | + let xs = xs.transpose(1, 2)?; |
| 59 | + xs.unsqueeze(candle_core::D::Minus1) |
| 60 | + } |
| 61 | + |
| 62 | + pub fn forward(&self, xs: &Tensor) -> Result<Tensor> { |
| 63 | + let xs = self.linear.forward(xs)?; |
| 64 | + let xs = self.rearrange(&xs)?; |
| 65 | + candle_nn::ops::sigmoid(&xs) |
| 66 | + } |
| 67 | +} |
| 68 | + |
| 69 | +#[derive(Debug)] |
| 70 | +pub struct ToVGates { |
| 71 | + pub(crate) linear: Linear, |
| 72 | + #[allow(dead_code)] |
| 73 | + pub(crate) heads: usize, |
| 74 | +} |
| 75 | + |
| 76 | +impl ToVGates { |
| 77 | + pub fn new(vb: VarBuilder, dim: usize, heads: usize) -> Result<Self> { |
| 78 | + Ok(Self { |
| 79 | + linear: linear_no_bias(dim, heads, vb)?, |
| 80 | + heads, |
| 81 | + }) |
| 82 | + } |
| 83 | + |
| 84 | + pub fn rearrange(&self, xs: &Tensor) -> Result<Tensor> { |
| 85 | + let xs = xs.transpose(1, 2)?; |
| 86 | + xs.unsqueeze(candle_core::D::Minus1) |
| 87 | + } |
| 88 | + |
| 89 | + pub fn forward(&self, xs: &Tensor) -> Result<Tensor> { |
| 90 | + let xs = self.linear.forward(xs)?; |
| 91 | + let xs = candle_nn::ops::sigmoid(&xs)?; |
| 92 | + self.rearrange(&xs) |
| 93 | + } |
| 94 | +} |
| 95 | + |
| 96 | +#[derive(Debug)] |
| 97 | +pub struct ToOut { |
| 98 | + pub(crate) drop_p: f64, |
| 99 | + pub(crate) linear: Linear, |
| 100 | +} |
| 101 | + |
| 102 | +impl ToOut { |
| 103 | + pub fn new( |
| 104 | + vb: VarBuilder, |
| 105 | + dim: usize, |
| 106 | + heads: usize, |
| 107 | + dim_head: usize, |
| 108 | + drop_p: Option<f64>, |
| 109 | + ) -> Result<Self> { |
| 110 | + Ok(Self { |
| 111 | + drop_p: drop_p.unwrap_or(0.0), |
| 112 | + linear: linear_no_bias(dim_head * heads, dim, vb)?, |
| 113 | + }) |
| 114 | + } |
| 115 | + |
| 116 | + pub fn rearrange(&self, xs: &Tensor) -> Result<Tensor> { |
| 117 | + let xs_dims = xs.dims(); |
| 118 | + let (b, h, n, d) = (xs_dims[0], xs_dims[1], xs_dims[2], xs_dims[3]); |
| 119 | + xs.permute((0, 2, 1, 3))?.reshape((b, n, h * d)) |
| 120 | + } |
| 121 | + |
| 122 | + pub fn forward_t(&self, xs: &Tensor, train: bool) -> Result<Tensor> { |
| 123 | + let xs = self.rearrange(xs)?; |
| 124 | + let xs = self.linear.forward(&xs)?; |
| 125 | + if train && self.drop_p > 0.0 { |
| 126 | + candle_nn::ops::dropout(&xs, self.drop_p as f32) |
| 127 | + } else { |
| 128 | + Ok(xs) |
| 129 | + } |
| 130 | + } |
| 131 | +} |
| 132 | + |
| 133 | +#[derive(Debug)] |
| 134 | +pub struct Attention { |
| 135 | + #[allow(dead_code)] |
| 136 | + scale: f64, |
| 137 | + #[allow(dead_code)] |
| 138 | + drop_p: f64, |
| 139 | + norm: LayerNorm, |
| 140 | + pub(crate) to_qkv: ToQKV, |
| 141 | + pub(crate) to_value_residual_mix: Option<ToValueResidualMix>, |
| 142 | + pub(crate) to_v_gates: ToVGates, |
| 143 | + attend: Attend, |
| 144 | + to_out: ToOut, |
| 145 | + #[allow(dead_code)] |
| 146 | + learned_value_residual_mix: bool, |
| 147 | +} |
| 148 | + |
| 149 | +impl Attention { |
| 150 | + pub fn new( |
| 151 | + vb: VarBuilder, |
| 152 | + dim: usize, |
| 153 | + dim_head: Option<usize>, |
| 154 | + heads: Option<usize>, |
| 155 | + drop_p: Option<f64>, |
| 156 | + is_flash: Option<bool>, |
| 157 | + learned_value_residual_mix: Option<bool>, |
| 158 | + ) -> Result<Self> { |
| 159 | + let dim_head = dim_head.unwrap_or(32); |
| 160 | + let heads = heads.unwrap_or(4); |
| 161 | + let scale = (dim_head as f64).sqrt(); |
| 162 | + |
| 163 | + let norm = layer_norm(dim, LayerNormConfig::default(), vb.pp("norm"))?; |
| 164 | + let to_qkv = ToQKV::new(vb.pp("to_qkv"), dim, dim_head * heads, heads)?; |
| 165 | + let to_value_residual_mix = if learned_value_residual_mix.unwrap_or(false) { |
| 166 | + Some(ToValueResidualMix::new( |
| 167 | + vb.pp("to_value_residual_mix"), |
| 168 | + dim, |
| 169 | + heads, |
| 170 | + )?) |
| 171 | + } else { |
| 172 | + None |
| 173 | + }; |
| 174 | + let to_v_gates = ToVGates::new(vb.pp("to_v_gates"), dim, heads)?; |
| 175 | + let to_out = ToOut::new(vb.pp("to_out"), dim, heads, dim_head, drop_p)?; |
| 176 | + |
| 177 | + Ok(Self { |
| 178 | + scale, |
| 179 | + drop_p: drop_p.unwrap_or(0.0), |
| 180 | + norm, |
| 181 | + to_qkv, |
| 182 | + to_value_residual_mix, |
| 183 | + to_v_gates, |
| 184 | + attend: Attend::new(drop_p, None, None, is_flash, None), |
| 185 | + to_out, |
| 186 | + learned_value_residual_mix: learned_value_residual_mix.unwrap_or(false), |
| 187 | + }) |
| 188 | + } |
| 189 | + |
| 190 | + pub fn forward_t( |
| 191 | + &self, |
| 192 | + xs: &Tensor, |
| 193 | + value_residual: Option<&Tensor>, |
| 194 | + train: bool, |
| 195 | + ) -> Result<(Tensor, Tensor)> { |
| 196 | + let xs = self.norm.forward(xs)?; |
| 197 | + let (q, k, mut v) = self.to_qkv.forward(&xs)?; |
| 198 | + let cache_v = v.clone(); |
| 199 | + |
| 200 | + if let Some(ref to_value_residual_mix) = self.to_value_residual_mix { |
| 201 | + if let Some(value_residual) = value_residual { |
| 202 | + let mix = to_value_residual_mix.forward(&xs)?; |
| 203 | + let diff = value_residual.sub(&v)?; |
| 204 | + let mix = mix.broadcast_as(diff.dims())?; |
| 205 | + let weighted = diff.mul(&mix)?; |
| 206 | + v = v.add(&weighted)?; |
| 207 | + } |
| 208 | + } |
| 209 | + |
| 210 | + let out = self.attend.forward_t(&q, &k, &v, train)?; |
| 211 | + let gates = self.to_v_gates.forward(&xs)?; |
| 212 | + let gates = gates.broadcast_as(out.dims())?; |
| 213 | + let out = out.mul(&gates)?; |
| 214 | + let out = self.to_out.forward_t(&out, train)?; |
| 215 | + |
| 216 | + Ok((out, cache_v)) |
| 217 | + } |
| 218 | +} |
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