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| 1 | +use candle::{DType, Device, Result, Tensor, D}; |
| 2 | +use candle_nn::VarBuilder; |
| 3 | + |
| 4 | +#[derive(Debug)] |
| 5 | +pub struct LayerNorm { |
| 6 | + weight: Tensor, |
| 7 | + bias: Tensor, |
| 8 | + epsilon: f32, |
| 9 | + span: tracing::Span, |
| 10 | +} |
| 11 | + |
| 12 | +impl LayerNorm { |
| 13 | + pub fn load(vb: VarBuilder, hidden_size: usize, epsilon: f32) -> Result<Self> { |
| 14 | + Ok(Self { |
| 15 | + weight: vb |
| 16 | + .get(hidden_size, "weight") |
| 17 | + .or_else(|_| vb.get(hidden_size, "gamma"))?, |
| 18 | + bias: vb |
| 19 | + .get(hidden_size, "bias") |
| 20 | + .or_else(|_| vb.get(hidden_size, "beta"))?, |
| 21 | + epsilon, |
| 22 | + span: tracing::span!(tracing::Level::TRACE, "layer-norm"), |
| 23 | + }) |
| 24 | + } |
| 25 | + |
| 26 | + pub fn forward(&self, hidden_states: &Tensor, residual: &Tensor) -> Result<Tensor> { |
| 27 | + let _enter = self.span.enter(); |
| 28 | + |
| 29 | + match hidden_states.device() { |
| 30 | + Device::Cpu => { |
| 31 | + let hidden_states = hidden_states.add(residual)?; |
| 32 | + let hidden_states_dtype = hidden_states.dtype(); |
| 33 | + let internal_dtype = match hidden_states_dtype { |
| 34 | + DType::F16 | DType::BF16 => DType::F32, |
| 35 | + d => d, |
| 36 | + }; |
| 37 | + let hidden_size = hidden_states.dim(D::Minus1)?; |
| 38 | + let hidden_states = hidden_states.to_dtype(internal_dtype)?; |
| 39 | + let mean_hidden_states = |
| 40 | + (hidden_states.sum_keepdim(D::Minus1)? / hidden_size as f64)?; |
| 41 | + let hidden_states = hidden_states.broadcast_sub(&mean_hidden_states)?; |
| 42 | + let norm_hidden_states = |
| 43 | + (hidden_states.sqr()?.sum_keepdim(D::Minus1)? / hidden_size as f64)?; |
| 44 | + let hidden_states_normed = hidden_states |
| 45 | + .broadcast_div(&(norm_hidden_states + self.epsilon as f64)?.sqrt()?)?; |
| 46 | + let hidden_states = hidden_states_normed |
| 47 | + .to_dtype(hidden_states_dtype)? |
| 48 | + .broadcast_mul(&self.weight)?; |
| 49 | + hidden_states.broadcast_add(&self.bias) |
| 50 | + } |
| 51 | + Device::Cuda(_) => { |
| 52 | + #[cfg(feature = "cuda")] |
| 53 | + { |
| 54 | + use candle_layer_norm::fused_add_layer_norm; |
| 55 | + |
| 56 | + let original_shape = hidden_states.shape(); |
| 57 | + let hidden_states = hidden_states.flatten_to(D::Minus2)?; |
| 58 | + let residual = residual.flatten_to(D::Minus2)?; |
| 59 | + |
| 60 | + let result = fused_add_layer_norm( |
| 61 | + &hidden_states, |
| 62 | + &residual, |
| 63 | + &self.weight, |
| 64 | + &self.bias, |
| 65 | + self.epsilon, |
| 66 | + )?; |
| 67 | + result.reshape(original_shape) |
| 68 | + } |
| 69 | + #[cfg(not(feature = "cuda"))] |
| 70 | + candle::bail!("`cuda` feature is not enabled") |
| 71 | + } |
| 72 | + } |
| 73 | + } |
| 74 | +} |
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