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|
use super::*;
use candle::{Device, Result, Tensor};
use half::f16;
use memmap2::MmapOptions;
use safetensors::{
tensor::{Dtype, TensorView},
SafeTensors,
};
use std::fs::File;
use std::path::PathBuf;
fn convert(view: TensorView<'_>, device: &Device) -> Result<Tensor> {
match view.dtype() {
Dtype::F16 => {
let v = view.data();
if (v.as_ptr() as usize) % 2 == 0 {
// SAFETY This is safe because we just checked that this
// was correctly aligned.
let data: &[f16] =
unsafe { std::slice::from_raw_parts(v.as_ptr() as *const f16, v.len() / 2) };
Tensor::from_slice(data, view.shape(), device)
} else {
let mut c = Vec::with_capacity(v.len() / 2);
let mut i = 0;
while i < v.len() {
c.push(f16::from_le_bytes([v[i], v[i + 1]]));
i += 2;
}
Tensor::from_slice(&c, view.shape(), device)
}
}
dt => todo!("Unhandled dtype {dt:?}"),
}
}
pub struct VarBuilder<'a> {
routing: HashMap<String, usize>,
safetensors: Vec<SafeTensors<'a>>,
device: Device,
}
impl<'a> VarBuilder<'a> {
pub fn new(safetensors: Vec<SafeTensors<'a>>, device: Device) -> Self {
let mut routing = HashMap::new();
for (index, sf) in safetensors.iter().enumerate() {
for k in sf.names() {
routing.insert(k.to_string(), index);
}
}
Self {
safetensors,
device,
routing,
}
}
pub fn get(&self, tensor_name: &str) -> Result<Tensor> {
// Unwrap or 0 just to let the proper error flow.
let index = self.routing.get(tensor_name).unwrap_or(&0);
let view = self.safetensors[*index].tensor(tensor_name).unwrap();
let tensor = convert(view, &self.device)?;
Ok(tensor)
}
}
impl Linear {
fn load(prefix: &str, vb: &VarBuilder) -> Result<Self> {
let weight = vb.get(&format!("{prefix}.weight"))?;
Ok(Self::new(weight))
}
fn load_multi(prefixes: &[&str], vb: &VarBuilder) -> Result<Self> {
let weights: Vec<_> = prefixes
.iter()
.map(|p| vb.get(&format!("{p}.weight")).unwrap())
.collect();
let weight = Tensor::cat(&weights, 0)?;
Ok(Self::new(weight))
}
}
impl RmsNorm {
fn load(prefix: &str, vb: &VarBuilder) -> Result<Self> {
let scale = vb.get(&format!("{prefix}.weight"))?;
Ok(Self::new(scale))
}
}
impl CausalSelfAttention {
fn load(prefix: &str, vb: &VarBuilder, cache: &Cache, config: &Config) -> Result<Self> {
let c_attn = Linear::load_multi(
&[
&format!("{prefix}.q_proj"),
&format!("{prefix}.k_proj"),
&format!("{prefix}.v_proj"),
],
vb,
)?;
let o_proj = Linear::load(&format!("{prefix}.o_proj"), vb)?;
Ok(Self::new(c_attn, o_proj, config.n_head, cache))
}
}
impl Mlp {
fn load(prefix: &str, vb: &VarBuilder) -> Result<Self> {
let c_fc1 = Linear::load(&format!("{prefix}.gate_proj"), vb)?;
let c_fc2 = Linear::load(&format!("{prefix}.up_proj"), vb)?;
let c_proj = Linear::load(&format!("{prefix}.down_proj"), vb)?;
Ok(Self::new(c_fc1, c_fc2, c_proj))
}
}
impl Block {
fn load(prefix: &str, vb: &VarBuilder, cache: &Cache, config: &Config) -> Result<Self> {
let attn = CausalSelfAttention::load(&format!("{prefix}.self_attn"), vb, cache, config)?;
let mlp = Mlp::load(&format!("{prefix}.mlp"), vb)?;
let input_layernorm = RmsNorm::load(&format!("{prefix}.input_layernorm"), vb)?;
let post_attention_layernorm =
RmsNorm::load(&format!("{prefix}.post_attention_layernorm"), vb)?;
Ok(Self::new(
input_layernorm,
attn,
post_attention_layernorm,
mlp,
))
}
}
impl Llama {
pub fn load(
device: &Device,
filenames: &[PathBuf],
cache: &Cache,
config: &Config,
) -> Result<Self> {
let handles: Vec<_> = filenames
.iter()
.map(|f| {
let file = File::open(f).unwrap();
unsafe { MmapOptions::new().map(&file).unwrap() }
})
.collect();
let tensors: Vec<_> = handles
.iter()
.map(|h| {
let tensors = SafeTensors::deserialize(h).unwrap();
tensors
})
.collect();
let vb = VarBuilder::new(tensors, device.clone());
let embedding = vb.get("model.embed_tokens.weight")?;
let wte = Embedding::new(embedding);
let lm_head = Linear::load("lm_head", &vb)?;
let norm = RmsNorm::load("model.norm", &vb)?;
let blocks: Vec<_> = (0..config.n_layer)
.map(|i| Block::load(&format!("model.layers.{i}"), &vb, cache, config).unwrap())
.collect();
Ok(Self::new(wte, blocks, norm, lm_head))
}
}
|
