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//! A `VarBuilder` is used to retrieve variables used by a model. These variables can either come
//! from a pre-trained checkpoint, e.g. using `VarBuilder::from_mmaped_safetensors`, or initialized
//! for training, e.g. using `VarBuilder::from_varmap`.
use crate::VarMap;
use candle::{safetensors::Load, DType, Device, Error, Result, Shape, Tensor};
use safetensors::{slice::IndexOp, tensor::SafeTensors};
use std::collections::HashMap;
use std::sync::Arc;
/// A structure used to retrieve variables, these variables can either come from storage or be
/// generated via some form of initialization.
///
/// The way to retrieve variables is defined in the backend embedded in the `VarBuilder`.
pub struct VarBuilderArgs<'a, B: Backend> {
data: Arc<TensorData<B>>,
path: Vec<String>,
_phantom: std::marker::PhantomData<&'a B>,
}
impl<'a, B: Backend> Clone for VarBuilderArgs<'a, B> {
fn clone(&self) -> Self {
Self {
data: self.data.clone(),
path: self.path.clone(),
_phantom: self._phantom,
}
}
}
/// A simple `VarBuilder`, this is less generic than `VarBuilderArgs` but should cover most common
/// use cases.
pub type VarBuilder<'a> = VarBuilderArgs<'a, Box<dyn SimpleBackend + 'a>>;
struct TensorData<B: Backend> {
backend: B,
pub dtype: DType,
pub device: Device,
}
/// A trait that defines how tensor data is retrieved.
///
/// Typically this would use disk storage in some specific format, or random initialization.
/// Note that there is a specialized version of this trait (`SimpleBackend`) that can be used most
/// of the time. The main restriction is that it doesn't allow for specific args (besides
/// initialization hints).
pub trait Backend: Send + Sync {
type Hints: Default;
/// Retrieve a tensor with some target shape.
fn get(
&self,
s: Shape,
name: &str,
h: Self::Hints,
dtype: DType,
dev: &Device,
) -> Result<Tensor>;
fn contains_tensor(&self, name: &str) -> bool;
}
pub trait SimpleBackend: Send + Sync {
/// Retrieve a tensor based on a target name and shape.
fn get(
&self,
s: Shape,
name: &str,
h: crate::Init,
dtype: DType,
dev: &Device,
) -> Result<Tensor>;
fn contains_tensor(&self, name: &str) -> bool;
}
impl<'a> Backend for Box<dyn SimpleBackend + 'a> {
type Hints = crate::Init;
fn get(
&self,
s: Shape,
name: &str,
h: Self::Hints,
dtype: DType,
dev: &Device,
) -> Result<Tensor> {
self.as_ref().get(s, name, h, dtype, dev)
}
fn contains_tensor(&self, name: &str) -> bool {
self.as_ref().contains_tensor(name)
}
}
impl<'a, B: Backend> VarBuilderArgs<'a, B> {
pub fn new_with_args(backend: B, dtype: DType, dev: &Device) -> Self {
let data = TensorData {
backend,
dtype,
device: dev.clone(),
};
Self {
data: Arc::new(data),
path: vec![],
_phantom: std::marker::PhantomData,
}
}
/// Returns the prefix of the `VarBuilder`.
pub fn prefix(&self) -> String {
self.path.join(".")
}
/// Returns a new `VarBuilder` using the root path.
pub fn root(&self) -> Self {
Self {
data: self.data.clone(),
path: vec![],
_phantom: std::marker::PhantomData,
}
}
/// Returns a new `VarBuilder` with the prefix set to `prefix`.
pub fn set_prefix(&self, prefix: impl ToString) -> Self {
Self {
data: self.data.clone(),
path: vec![prefix.to_string()],
_phantom: std::marker::PhantomData,
}
}
/// Return a new `VarBuilder` adding `s` to the current prefix. This can be think of as `cd`
/// into a directory.
pub fn push_prefix<S: ToString>(&self, s: S) -> Self {
let mut path = self.path.clone();
path.push(s.to_string());
Self {
data: self.data.clone(),
path,
_phantom: std::marker::PhantomData,
}
}
/// Short alias for `push_prefix`.
pub fn pp<S: ToString>(&self, s: S) -> Self {
self.push_prefix(s)
}
/// The device used by default.
pub fn device(&self) -> &Device {
&self.data.device
}
/// The dtype used by default.
pub fn dtype(&self) -> DType {
self.data.dtype
}
fn path(&self, tensor_name: &str) -> String {
if self.path.is_empty() {
tensor_name.to_string()
} else {
[&self.path.join("."), tensor_name].join(".")
}
}
/// This returns true only if a tensor with the passed in name is available. E.g. when passed
/// `a`, true is returned if `prefix.a` exists but false is returned if only `prefix.a.b`
/// exists.
pub fn contains_tensor(&self, tensor_name: &str) -> bool {
let path = self.path(tensor_name);
self.data.backend.contains_tensor(&path)
}
/// Retrieve the tensor associated with the given name at the current path.
pub fn get_with_hints<S: Into<Shape>>(
&self,
s: S,
name: &str,
hints: B::Hints,
) -> Result<Tensor> {
self.get_with_hints_dtype(s, name, hints, self.data.dtype)
}
/// Retrieve the tensor associated with the given name at the current path.
pub fn get<S: Into<Shape>>(&self, s: S, name: &str) -> Result<Tensor> {
self.get_with_hints(s, name, Default::default())
}
/// Retrieve the tensor associated with the given name & dtype at the current path.
pub fn get_with_hints_dtype<S: Into<Shape>>(
&self,
s: S,
name: &str,
hints: B::Hints,
dtype: DType,
) -> Result<Tensor> {
let path = self.path(name);
self.data
.backend
.get(s.into(), &path, hints, dtype, &self.data.device)
}
}
struct Zeros;
impl SimpleBackend for Zeros {
fn get(&self, s: Shape, _: &str, _: crate::Init, dtype: DType, dev: &Device) -> Result<Tensor> {
Tensor::zeros(s, dtype, dev)
}
fn contains_tensor(&self, _name: &str) -> bool {
true
}
}
impl SimpleBackend for HashMap<String, Tensor> {
fn get(
&self,
s: Shape,
name: &str,
_: crate::Init,
dtype: DType,
dev: &Device,
) -> Result<Tensor> {
let tensor = self
.get(name)
.ok_or_else(|| {
Error::CannotFindTensor {
path: name.to_string(),
}
.bt()
})?
.clone();
if tensor.shape() != &s {
Err(candle::Error::UnexpectedShape {
msg: format!("shape mismatch for {name}"),
expected: s,
got: tensor.shape().clone(),
}
.bt())?
}
tensor.to_device(dev)?.to_dtype(dtype)
}
fn contains_tensor(&self, name: &str) -> bool {
self.contains_key(name)
}
}
impl SimpleBackend for VarMap {
fn get(
&self,
s: Shape,
name: &str,
h: crate::Init,
dtype: DType,
dev: &Device,
) -> Result<Tensor> {
VarMap::get(self, s, name, h, dtype, dev)
}
fn contains_tensor(&self, name: &str) -> bool {
self.data().lock().unwrap().contains_key(name)
}
}
struct SafeTensorWithRouting<'a> {
routing: HashMap<String, usize>,
safetensors: Vec<SafeTensors<'a>>,
}
impl<'a> SimpleBackend for SafeTensorWithRouting<'a> {
fn get(
&self,
s: Shape,
path: &str,
_: crate::Init,
dtype: DType,
dev: &Device,
) -> Result<Tensor> {
let index = self.routing.get(path).ok_or_else(|| {
Error::CannotFindTensor {
path: path.to_string(),
}
.bt()
})?;
let tensor = self.safetensors[*index]
.tensor(path)?
.load(dev)?
.to_dtype(dtype)?;
if tensor.shape() != &s {
Err(candle::Error::UnexpectedShape {
msg: format!("shape mismatch for {path}"),
expected: s,
got: tensor.shape().clone(),
}
.bt())?
}
Ok(tensor)
}
fn contains_tensor(&self, name: &str) -> bool {
self.routing.contains_key(name)
}
}
impl SimpleBackend for candle::npy::NpzTensors {
fn get(
&self,
s: Shape,
path: &str,
_: crate::Init,
dtype: DType,
dev: &Device,
) -> Result<Tensor> {
let tensor = match self.get(path)? {
None => Err(Error::CannotFindTensor {
path: path.to_string(),
}
.bt())?,
Some(tensor) => tensor,
};
let tensor = tensor.to_device(dev)?.to_dtype(dtype)?;
if tensor.shape() != &s {
Err(candle::Error::UnexpectedShape {
msg: format!("shape mismatch for {path}"),
expected: s,
got: tensor.shape().clone(),
}
.bt())?
}
Ok(tensor)
}
fn contains_tensor(&self, name: &str) -> bool {
self.get(name).map_or(false, |v| v.is_some())
}
}
impl SimpleBackend for candle::pickle::PthTensors {
fn get(
&self,
s: Shape,
path: &str,
_: crate::Init,
dtype: DType,
dev: &Device,
) -> Result<Tensor> {
let tensor = match self.get(path)? {
None => Err(Error::CannotFindTensor {
path: path.to_string(),
}
.bt())?,
Some(tensor) => tensor,
};
let tensor = tensor.to_device(dev)?.to_dtype(dtype)?;
if tensor.shape() != &s {
Err(candle::Error::UnexpectedShape {
msg: format!("shape mismatch for {path}"),
expected: s,
got: tensor.shape().clone(),
}
.bt())?
}
Ok(tensor)
}
fn contains_tensor(&self, name: &str) -> bool {
self.get(name).map_or(false, |v| v.is_some())
}
}
impl SimpleBackend for candle::safetensors::MmapedSafetensors {
fn get(
&self,
s: Shape,
name: &str,
_: crate::Init,
dtype: DType,
dev: &Device,
) -> Result<Tensor> {
let tensor = self.load(name, dev)?.to_dtype(dtype)?;
if tensor.shape() != &s {
Err(candle::Error::UnexpectedShape {
msg: format!("shape mismatch for {name}"),
expected: s,
got: tensor.shape().clone(),
}
.bt())?
}
Ok(tensor)
}
fn contains_tensor(&self, name: &str) -> bool {
self.get(name).is_ok()
}
}
impl SimpleBackend for candle::safetensors::BufferedSafetensors {
fn get(
&self,
s: Shape,
name: &str,
_: crate::Init,
dtype: DType,
dev: &Device,
) -> Result<Tensor> {
let tensor = self.load(name, dev)?.to_dtype(dtype)?;
if tensor.shape() != &s {
Err(candle::Error::UnexpectedShape {
msg: format!("shape mismatch for {name}"),
expected: s,
got: tensor.shape().clone(),
}
.bt())?
}
Ok(tensor)
}
fn contains_tensor(&self, name: &str) -> bool {
self.get(name).is_ok()
}
}
impl<'a> VarBuilder<'a> {
/// Initializes a `VarBuilder` using a custom backend.
///
/// It is preferred to use one of the more specific constructors. This
/// constructor is provided to allow downstream users to define their own
/// backends.
pub fn from_backend(
backend: Box<dyn SimpleBackend + 'a>,
dtype: DType,
device: Device,
) -> Self {
let data = TensorData {
backend,
dtype,
device,
};
Self {
data: Arc::new(data),
path: vec![],
_phantom: std::marker::PhantomData,
}
}
/// Initializes a `VarBuilder` that uses zeros for any tensor.
pub fn zeros(dtype: DType, dev: &Device) -> Self {
Self::from_backend(Box::new(Zeros), dtype, dev.clone())
}
/// Initializes a `VarBuilder` that retrieves tensors stored in a hashtable. An error is
/// returned if no tensor is available under the requested path or on shape mismatches.
pub fn from_tensors(ts: HashMap<String, Tensor>, dtype: DType, dev: &Device) -> Self {
Self::from_backend(Box::new(ts), dtype, dev.clone())
}
/// Initializes a `VarBuilder` using a `VarMap`. The requested tensors are created and
/// initialized on new paths, the same tensor is used if the same path is requested multiple
/// times. This is commonly used when initializing a model before training.
///
/// Note that it is possible to load the tensor values after model creation using the `load`
/// method on `varmap`, this can be used to start model training from an existing checkpoint.
pub fn from_varmap(varmap: &VarMap, dtype: DType, dev: &Device) -> Self {
Self::from_backend(Box::new(varmap.clone()), dtype, dev.clone())
}
/// Initializes a `VarBuilder` that retrieves tensors stored in a collection of safetensors
/// files.
///
/// # Safety
///
/// The unsafe is inherited from [`memmap2::MmapOptions`].
pub unsafe fn from_mmaped_safetensors<P: AsRef<std::path::Path>>(
paths: &[P],
dtype: DType,
dev: &Device,
) -> Result<Self> {
let tensors = candle::safetensors::MmapedSafetensors::multi(paths)?;
Ok(Self::from_backend(Box::new(tensors), dtype, dev.clone()))
}
/// Initializes a `VarBuilder` from a binary builder in the safetensor format.
pub fn from_buffered_safetensors(data: Vec<u8>, dtype: DType, dev: &Device) -> Result<Self> {
let tensors = candle::safetensors::BufferedSafetensors::new(data)?;
Ok(Self::from_backend(Box::new(tensors), dtype, dev.clone()))
}
/// Initializes a `VarBuilder` that retrieves tensors stored in a numpy npz file.
pub fn from_npz<P: AsRef<std::path::Path>>(p: P, dtype: DType, dev: &Device) -> Result<Self> {
let npz = candle::npy::NpzTensors::new(p)?;
Ok(Self::from_backend(Box::new(npz), dtype, dev.clone()))
}
/// Initializes a `VarBuilder` that retrieves tensors stored in a pytorch pth file.
pub fn from_pth<P: AsRef<std::path::Path>>(p: P, dtype: DType, dev: &Device) -> Result<Self> {
let pth = candle::pickle::PthTensors::new(p, None)?;
Ok(Self::from_backend(Box::new(pth), dtype, dev.clone()))
}
/// Gets a VarBuilder that applies some renaming function on tensor it gets queried for before
/// passing the new names to the inner VarBuilder.
///
/// ```rust
/// use candle::{Tensor, DType, Device};
///
/// let a = Tensor::arange(0f32, 6f32, &Device::Cpu)?.reshape((2, 3))?;
/// let tensors: std::collections::HashMap<_, _> = [
/// ("foo".to_string(), a),
/// ]
/// .into_iter()
/// .collect();
/// let vb = candle_nn::VarBuilder::from_tensors(tensors, DType::F32, &Device::Cpu);
/// assert!(vb.contains_tensor("foo"));
/// assert!(vb.get((2, 3), "foo").is_ok());
/// assert!(!vb.contains_tensor("bar"));
/// let vb = vb.rename_f(|f: &str| if f == "bar" { "foo".to_string() } else { f.to_string() });
/// assert!(vb.contains_tensor("bar"));
/// assert!(vb.contains_tensor("foo"));
/// assert!(vb.get((2, 3), "bar").is_ok());
/// assert!(vb.get((2, 3), "foo").is_ok());
/// assert!(!vb.contains_tensor("baz"));
/// # Ok::<(), candle::Error>(())
/// ```
pub fn rename_f<F: Fn(&str) -> String + Sync + Send + 'static>(self, f: F) -> Self {
let f: Box<dyn Fn(&str) -> String + Sync + Send + 'static> = Box::new(f);
self.rename(f)
}
pub fn rename<R: Renamer + Send + Sync + 'a>(self, renamer: R) -> Self {
let dtype = self.dtype();
let device = self.device().clone();
let path = self.path.clone();
let backend = Rename::new(self, renamer);
let backend: Box<dyn SimpleBackend + 'a> = Box::new(backend);
let data = TensorData {
backend,
dtype,
device,
};
Self {
data: Arc::new(data),
path,
_phantom: std::marker::PhantomData,
}
}
}
pub struct ShardedSafeTensors(candle::safetensors::MmapedSafetensors);
pub type ShardedVarBuilder<'a> = VarBuilderArgs<'a, ShardedSafeTensors>;
impl ShardedSafeTensors {
/// Initializes a `VarBuilder` that retrieves tensors stored in a collection of safetensors
/// files and make them usable in a sharded way.
///
/// # Safety
///
/// The unsafe is inherited from [`memmap2::MmapOptions`].
pub unsafe fn var_builder<P: AsRef<std::path::Path>>(
paths: &[P],
dtype: DType,
dev: &Device,
) -> Result<ShardedVarBuilder<'static>> {
let tensors = candle::safetensors::MmapedSafetensors::multi(paths)?;
let backend = ShardedSafeTensors(tensors);
Ok(VarBuilderArgs::new_with_args(backend, dtype, dev))
}
}
#[derive(Debug, Clone, Copy, Eq, PartialEq)]
pub struct Shard {
pub dim: usize,
pub rank: usize,
pub world_size: usize,
}
impl Default for Shard {
fn default() -> Self {
Self {
dim: 0,
rank: 0,
world_size: 1,
}
}
}
/// Get part of a tensor, typically used to do Tensor Parallelism sharding.
///
/// If the tensor is of size (1024, 1024).
///
/// `dim` corresponds to the dimension to slice into
/// `rank` is the rank of the current process
/// `world_size` is the total number of ranks in the process group
///
/// `get_sharded("tensor", 0, 0, 2)` means `tensor.i((..512))`
/// `get_sharded("tensor", 0, 1, 2)` means `tensor.i((512..))`
/// `get_sharded("tensor", 1, 0, 2)` means `tensor.i((.., ..512))`
impl Backend for ShardedSafeTensors {
type Hints = Shard;
fn get(
&self,
target_shape: Shape, // The size is only checked when the world size is 1.
path: &str,
h: Self::Hints,
dtype: DType,
dev: &Device,
) -> Result<Tensor> {
if h.world_size == 1 {
// There is no sharding to be applied here so we use the default backend to speed
// things up.
return SimpleBackend::get(&self.0, target_shape, path, Default::default(), dtype, dev);
}
let Shard {
dim,
rank,
world_size,
} = h;
let view = self.0.get(path)?;
let view_dtype = view.dtype();
let mut shape = view.shape().to_vec();
let size = shape[dim];
if size % world_size != 0 {
return Err(Error::ShapeMismatchSplit {
shape: shape.into(),
dim,
n_parts: world_size,
});
}
let block_size = size / world_size;
let start = rank * block_size;
let stop = (rank + 1) * block_size;
// Everything is expressed in tensor dimension
// bytes offsets is handled automatically for safetensors.
let iterator = if dim == 0 {
view.slice(start..stop).map_err(|_| {
Error::Msg(format!(
"Cannot slice tensor {path} ({shape:?} along dim {dim} with {start}..{stop}"
))
})?
} else if dim == 1 {
view.slice((.., start..stop)).map_err(|_| {
Error::Msg(format!(
"Cannot slice tensor {path} ({shape:?} along dim {dim} with {start}..{stop}"
))
})?
} else {
candle::bail!("Get sharded on dimensions != 0 or 1")
};
shape[dim] = block_size;
let view_dtype: DType = view_dtype.try_into()?;
let raw: Vec<u8> = iterator.into_iter().flatten().cloned().collect();
Tensor::from_raw_buffer(&raw, view_dtype, &shape, dev)?.to_dtype(dtype)
}
fn contains_tensor(&self, name: &str) -> bool {
self.0.get(name).is_ok()
}
}
/// This traits specifies a way to rename the queried names into names that are stored in an inner
/// VarBuilder.
pub trait Renamer {
/// This is applied to the name obtained by a name call and the resulting name is passed to the
/// inner VarBuilder.
fn rename(&self, v: &str) -> std::borrow::Cow<'_, str>;
}
pub struct Rename<'a, R: Renamer> {
inner: VarBuilder<'a>,
renamer: R,
}
impl<'a, R: Renamer + Sync + Send> SimpleBackend for Rename<'a, R> {
fn get(
&self,
s: Shape,
name: &str,
h: crate::Init,
dtype: DType,
dev: &Device,
) -> Result<Tensor> {
let name = self.renamer.rename(name);
self.inner
.get_with_hints_dtype(s, &name, h, dtype)?
.to_device(dev)
}
fn contains_tensor(&self, name: &str) -> bool {
let name = self.renamer.rename(name);
self.inner.contains_tensor(&name)
}
}
impl<'a, R: Renamer> Rename<'a, R> {
pub fn new(inner: VarBuilder<'a>, renamer: R) -> Self {
Self { inner, renamer }
}
}
impl Renamer for Box<dyn Fn(&str) -> String + Sync + Send> {
fn rename(&self, v: &str) -> std::borrow::Cow<'_, str> {
std::borrow::Cow::Owned(self(v))
}
}