use crate::models::with_tracing::{linear, linear_no_bias, Linear};
use candle::{DType, Device, Module, Result, Tensor, D};
use candle_nn::{Activation, LayerNorm, VarBuilder};
use serde::Deserialize;
use std::sync::Arc;
#[derive(Debug, Clone, PartialEq, Deserialize)]
pub struct Config {
pub(crate) vocab_size: usize,
pub(crate) intermediate_size: usize,
pub(crate) hidden_size: usize,
pub(crate) num_hidden_layers: usize,
pub(crate) num_attention_heads: usize,
pub(crate) num_key_value_heads: usize,
pub(crate) hidden_act: Activation,
pub(crate) partial_rotary_factor: f64,
pub(crate) rope_theta: f64,
pub(crate) max_position_embeddings: usize,
pub(crate) layer_norm_eps: f64,
pub(crate) use_cache: bool,
#[serde(default)]
pub(crate) use_qkv_bias: bool, #[serde(default)]
pub(crate) use_flash_attn: bool, }
impl Config {
pub fn stablelm_3b_4e1t(use_flash_attn: bool) -> Self {
Self {
vocab_size: 50304,
intermediate_size: 6912,
hidden_size: 2560,
num_hidden_layers: 32,
num_attention_heads: 32,
num_key_value_heads: 32,
hidden_act: Activation::Silu,
partial_rotary_factor: 0.25,
rope_theta: 10_000.,
max_position_embeddings: 4096,
layer_norm_eps: 1e-5,
use_qkv_bias: false,
use_cache: true,
use_flash_attn,
}
}
pub fn head_dim(&self) -> usize {
self.hidden_size / self.num_attention_heads
}
pub fn rotary_ndims(&self) -> usize {
(self.head_dim() as f64 * self.partial_rotary_factor) as usize
}
pub fn num_kv_groups(&self) -> usize {
self.num_attention_heads / self.num_key_value_heads
}
pub fn set_use_flash_attn(&mut self, use_flash_attn: bool) {
self.use_flash_attn = use_flash_attn
}
}
#[derive(Debug)]
pub(crate) struct RotaryEmbedding {
sin: Tensor,
cos: Tensor,
}
fn rotate_half(xs: &Tensor) -> Result<Tensor> {
let xs = xs.chunk(2, D::Minus1)?;
Tensor::cat(&[&xs[1].neg()?, &xs[0]], D::Minus1)
}
impl RotaryEmbedding {
pub(crate) fn new(dtype: DType, cfg: &Config, dev: &Device) -> Result<Self> {
let dim = cfg.rotary_ndims();
let max_seq_len = cfg.max_position_embeddings;
let inv_freq: Vec<_> = (0..dim)
.step_by(2)
.map(|i| 1f32 / cfg.rope_theta.powf(i as f64 / dim as f64) as f32)
.collect();
let inv_freq_len = inv_freq.len();
let inv_freq = Tensor::from_vec(inv_freq, (1, inv_freq_len), dev)?.to_dtype(dtype)?;
let t = Tensor::arange(0u32, max_seq_len as u32, dev)?
.to_dtype(dtype)?
.reshape((max_seq_len, 1))?;
let freqs = t.matmul(&inv_freq)?;
let freqs = Tensor::cat(&[&freqs, &freqs], D::Minus1)?;
Ok(Self {
sin: freqs.sin()?,
cos: freqs.cos()?,
})
}
pub(crate) fn apply_rotary_emb_qkv(
&self,
q: &Tensor,
k: &Tensor,
seqlen_offset: usize,
) -> Result<(Tensor, Tensor)> {
let (_b_sz, _h, seq_len, _n_embd) = q.dims4()?;
let cos = self.cos.narrow(0, seqlen_offset, seq_len)?;
let sin = self.sin.narrow(0, seqlen_offset, seq_len)?;
let cos = cos.unsqueeze(0)?.unsqueeze(0)?; let sin = sin.unsqueeze(0)?.unsqueeze(0)?; let q_embed = (q.broadcast_mul(&cos)? + rotate_half(q)?.broadcast_mul(&sin))?;
let k_embed = (k.broadcast_mul(&cos)? + rotate_half(k)?.broadcast_mul(&sin))?;
Ok((q_embed, k_embed))
}
}
#[derive(Debug)]
#[allow(clippy::upper_case_acronyms)]
struct MLP {
gate_proj: Linear,
up_proj: Linear,
down_proj: Linear,
act_fn: Activation,
span: tracing::Span,
}
impl MLP {
fn new(cfg: &Config, vb: VarBuilder) -> Result<Self> {
let hidden_sz = cfg.hidden_size;
let intermediate_sz = cfg.intermediate_size;
let gate_proj = linear_no_bias(hidden_sz, intermediate_sz, vb.pp("gate_proj"))?;
let up_proj = linear_no_bias(hidden_sz, intermediate_sz, vb.pp("up_proj"))?;
let down_proj = linear_no_bias(intermediate_sz, hidden_sz, vb.pp("down_proj"))?;
Ok(Self {
gate_proj,
up_proj,
down_proj,
act_fn: cfg.hidden_act,
span: tracing::span!(tracing::Level::TRACE, "mlp"),
})
}
}
impl Module for MLP {
fn forward(&self, xs: &Tensor) -> Result<Tensor> {
let _enter = self.span.enter();
let lhs = xs.apply(&self.gate_proj)?.apply(&self.act_fn)?;
let rhs = xs.apply(&self.up_proj)?;
(lhs * rhs)?.apply(&self.down_proj)
}
}
#[cfg(feature = "flash-attn")]
fn flash_attn(
q: &Tensor,
k: &Tensor,
v: &Tensor,
softmax_scale: f32,
causal: bool,
) -> Result<Tensor> {
candle_flash_attn::flash_attn(q, k, v, softmax_scale, causal)
}
#[cfg(not(feature = "flash-attn"))]
fn flash_attn(_: &Tensor, _: &Tensor, _: &Tensor, _: f32, _: bool) -> Result<Tensor> {
unimplemented!("compile with '--features flash-attn'")
}
#[derive(Debug)]
struct Attention {
q_proj: Linear,
k_proj: Linear,
v_proj: Linear,
o_proj: Linear,
num_heads: usize,
num_kv_heads: usize,
num_kv_groups: usize,
head_dim: usize,
hidden_size: usize,
rotary_emb: Arc<RotaryEmbedding>,
kv_cache: Option<(Tensor, Tensor)>,
use_cache: bool,
rotary_ndims: usize,
use_flash_attn: bool,
span: tracing::Span,
}
impl Attention {
fn new(rotary_emb: Arc<RotaryEmbedding>, cfg: &Config, vb: VarBuilder) -> Result<Self> {
let hidden_sz = cfg.hidden_size;
let head_dim = cfg.head_dim();
let num_heads = cfg.num_attention_heads;
let num_kv_heads = cfg.num_key_value_heads;
let linear_layer = if cfg.use_qkv_bias {
linear
} else {
linear_no_bias
};
let q_proj = linear_layer(hidden_sz, num_heads * head_dim, vb.pp("q_proj"))?;
let k_proj = linear_layer(hidden_sz, num_kv_heads * head_dim, vb.pp("k_proj"))?;
let v_proj = linear_layer(hidden_sz, num_kv_heads * head_dim, vb.pp("v_proj"))?;
let o_proj = linear_no_bias(num_heads * head_dim, hidden_sz, vb.pp("o_proj"))?;
Ok(Self {
q_proj,
k_proj,
v_proj,
o_proj,
num_heads,
num_kv_heads,
num_kv_groups: cfg.num_kv_groups(),
head_dim,
hidden_size: hidden_sz,
rotary_emb,
kv_cache: None,
use_cache: cfg.use_cache,
rotary_ndims: cfg.rotary_ndims(),
use_flash_attn: cfg.use_flash_attn,
span: tracing::span!(tracing::Level::TRACE, "attn"),
})
}
fn forward(
&mut self,
xs: &Tensor,
attention_mask: Option<&Tensor>,
seqlen_offset: usize,
) -> Result<Tensor> {
let _enter = self.span.enter();
let (b_sz, q_len, _) = xs.dims3()?;
let query_states = self.q_proj.forward(xs)?;
let key_states = self.k_proj.forward(xs)?;
let value_states = self.v_proj.forward(xs)?;
let query_states = query_states
.reshape((b_sz, q_len, self.num_heads, self.head_dim))?
.transpose(1, 2)?;
let key_states = key_states
.reshape((b_sz, q_len, self.num_kv_heads, self.head_dim))?
.transpose(1, 2)?;
let value_states = value_states
.reshape((b_sz, q_len, self.num_kv_heads, self.head_dim))?
.transpose(1, 2)?;
let (rot_ndims, pass_ndims) = (self.rotary_ndims, self.head_dim - self.rotary_ndims);
let query_rot = query_states.narrow(D::Minus1, 0, rot_ndims)?;
let query_pass = query_states.narrow(D::Minus1, rot_ndims, pass_ndims)?;
let key_rot = key_states.narrow(D::Minus1, 0, rot_ndims)?;
let key_pass = key_states.narrow(D::Minus1, rot_ndims, pass_ndims)?;
let (query_rot, key_rot) =
self.rotary_emb
.apply_rotary_emb_qkv(&query_rot, &key_rot, seqlen_offset)?;
let query_states = Tensor::cat(&[query_rot, query_pass], D::Minus1)?.contiguous()?;
let key_states = Tensor::cat(&[key_rot, key_pass], D::Minus1)?.contiguous()?;
let (key_states, value_states) = match &self.kv_cache {
None => (key_states, value_states),
Some((prev_k, prev_v)) => {
let key_states = Tensor::cat(&[prev_k, &key_states], 2)?;
let value_states = Tensor::cat(&[prev_v, &value_states], 2)?;
(key_states, value_states)
}
};
if self.use_cache {
self.kv_cache = Some((key_states.clone(), value_states.clone()));
}
let key_states = crate::utils::repeat_kv(key_states, self.num_kv_groups)?.contiguous()?;
let value_states =
crate::utils::repeat_kv(value_states, self.num_kv_groups)?.contiguous()?;
let attn_output = if self.use_flash_attn {
let q = query_states.transpose(1, 2)?;
let k = key_states.transpose(1, 2)?;
let v = value_states.transpose(1, 2)?;
let softmax_scale = 1f32 / (self.head_dim as f32).sqrt();
flash_attn(&q, &k, &v, softmax_scale, q_len > 1)?.transpose(1, 2)?
} else {
let scale = 1f64 / f64::sqrt(self.head_dim as f64);
let attn_weights = (query_states.matmul(&key_states.transpose(2, 3)?)? * scale)?;
let attn_weights = match attention_mask {
None => attn_weights,
Some(mask) => attn_weights.broadcast_add(mask)?,
};
let attn_weights = candle_nn::ops::softmax_last_dim(&attn_weights)?;
attn_weights.matmul(&value_states)?
};
attn_output
.transpose(1, 2)?
.reshape((b_sz, q_len, self.hidden_size))?
.apply(&self.o_proj)
}
}
#[derive(Debug)]
struct DecoderLayer {
self_attn: Attention,
mlp: MLP,
input_layernorm: LayerNorm,
post_attention_layernorm: LayerNorm,
span: tracing::Span,
}
impl DecoderLayer {
fn new(rotary_emb: Arc<RotaryEmbedding>, cfg: &Config, vb: VarBuilder) -> Result<Self> {
let self_attn = Attention::new(rotary_emb, cfg, vb.pp("self_attn"))?;
let mlp = MLP::new(cfg, vb.pp("mlp"))?;
let input_layernorm = candle_nn::layer_norm(
cfg.hidden_size,
cfg.layer_norm_eps,
vb.pp("input_layernorm"),
)?;
let post_attention_layernorm = candle_nn::layer_norm(
cfg.hidden_size,
cfg.layer_norm_eps,
vb.pp("post_attention_layernorm"),
)?;
Ok(Self {
self_attn,
mlp,
input_layernorm,
post_attention_layernorm,
span: tracing::span!(tracing::Level::TRACE, "layer"),
})
}
fn forward(
&mut self,
xs: &Tensor,
attention_mask: Option<&Tensor>,
seqlen_offset: usize,
) -> Result<Tensor> {
let _enter = self.span.enter();
let residual = xs;
let xs = self.input_layernorm.forward(xs)?;
let xs = self.self_attn.forward(&xs, attention_mask, seqlen_offset)?;
let xs = (xs + residual)?;
let residual = &xs;
let xs = xs.apply(&self.post_attention_layernorm)?.apply(&self.mlp)?;
residual + xs
}
}
#[derive(Debug)]
pub struct Model {
embed_tokens: candle_nn::Embedding,
layers: Vec<DecoderLayer>,
norm: LayerNorm,
lm_head: Linear,
device: Device,
dtype: DType,
span: tracing::Span,
}
impl Model {
pub fn new(cfg: &Config, vb: VarBuilder) -> Result<Self> {
let vb_m = vb.pp("model");
let embed_tokens =
candle_nn::embedding(cfg.vocab_size, cfg.hidden_size, vb_m.pp("embed_tokens"))?;
let rotary_emb = Arc::new(RotaryEmbedding::new(vb.dtype(), cfg, vb_m.device())?);
let mut layers = Vec::with_capacity(cfg.num_hidden_layers);
let vb_l = vb_m.pp("layers");
for layer_idx in 0..cfg.num_hidden_layers {
let layer = DecoderLayer::new(rotary_emb.clone(), cfg, vb_l.pp(layer_idx))?;
layers.push(layer)
}
let norm = candle_nn::layer_norm(cfg.hidden_size, cfg.layer_norm_eps, vb_m.pp("norm"))?;
let lm_head = linear_no_bias(cfg.hidden_size, cfg.vocab_size, vb.pp("lm_head"))?;
Ok(Self {
embed_tokens,
layers,
norm,
lm_head,
device: vb.device().clone(),
dtype: vb.dtype(),
span: tracing::span!(tracing::Level::TRACE, "model"),
})
}
fn prepare_decoder_attention_mask(
&self,
b_size: usize,
tgt_len: usize,
seqlen_offset: usize,
) -> Result<Tensor> {
let mask: Vec<_> = (0..tgt_len)
.flat_map(|i| (0..tgt_len).map(move |j| if i < j { f32::NEG_INFINITY } else { 0. }))
.collect();
let mask = Tensor::from_slice(&mask, (tgt_len, tgt_len), &self.device)?;
let mask = if seqlen_offset > 0 {
let mask0 = Tensor::zeros((tgt_len, seqlen_offset), DType::F32, &self.device)?;
Tensor::cat(&[&mask0, &mask], D::Minus1)?
} else {
mask
};
mask.expand((b_size, 1, tgt_len, tgt_len + seqlen_offset))?
.to_dtype(self.dtype)
}
pub fn forward(&mut self, input_ids: &Tensor, seqlen_offset: usize) -> Result<Tensor> {
let _enter = self.span.enter();
let (b_size, seq_len) = input_ids.dims2()?;
let attention_mask = if seq_len <= 1 {
None
} else {
let mask = self.prepare_decoder_attention_mask(b_size, seq_len, seqlen_offset)?;
Some(mask)
};
let mut xs = self.embed_tokens.forward(input_ids)?;
for layer in self.layers.iter_mut() {
xs = layer.forward(&xs, attention_mask.as_ref(), seqlen_offset)?
}
xs.narrow(1, seq_len - 1, 1)?
.apply(&self.norm)?
.apply(&self.lm_head)
}
}