candle

Candle is a minimalist ML framework for Rust with a focus on performance (including GPU support) and ease of use. Try our online demos: whisper, llama2.

let a = Tensor::randn(0f32, 1., (2, 3), &Device::Cpu)?;
let b = Tensor::randn(0f32, 1., (3, 4), &Device::Cpu)?;

let c = a.matmul(&b)?;
println!("{c}");

Check out our examples

Check out our examples:

• Whisper: speech recognition model.
• Llama and Llama-v2: general LLM.
• Falcon: general LLM.
• Bert: useful for sentence embeddings.
• StarCoder: LLM specialized to code generation.

Run them using the following commands:

cargo run --example whisper --release
cargo run --example llama --release
cargo run --example falcon --release
cargo run --example bert --release
cargo run --example bigcode --release

In order to use CUDA add --features cuda to the example command line.

There are also some wasm examples for whisper and llama2.c. You can either build them with trunk or try them online: whisper, llama2.

For llama2, run the following command to retrieve the weight files and start a test server:

cd candle-wasm-examples/llama2-c
wget https://huggingface.co/spaces/lmz/candle-llama2/resolve/main/model.bin
wget https://huggingface.co/spaces/lmz/candle-llama2/resolve/main/tokenizer.json
trunk serve --release --public-url /candle-llama2/ --port 8081

And then head over to http://localhost:8081/candle-llama2.

Features

• Simple syntax, looks and feels like PyTorch.
• CPU and Cuda backends, m1, f16, bf16.
• Serverless (on CPU), small and fast deployments
• WASM support, run your models in a browser.
• Model training.
• Distributed computing using NCCL.
• Model support out of the box: Llama, Whisper, Falcon, StarCoder...
• Embed user-defined ops/kernels, such as flash-attention v2.

How to use

Cheatsheet:

	Using PyTorch	Using Candle
Creation	torch.Tensor([[1, 2], [3, 4]])	Tensor::new(&[[1f32, 2.], [3., 4.]], &Device::Cpu)?
Creation	torch.zeros((2, 2))	Tensor::zeros((2, 2), DType::F32, &Device::Cpu)?
Indexing	tensor[:, :4]	tensor.i((.., ..4))?
Operations	tensor.view((2, 2))	tensor.reshape((2, 2))?
Operations	a.matmul(b)	a.matmul(&b)?
Arithmetic	a + b	&a + &b
Device	tensor.to(device="cuda")	tensor.to_device(&Device::Cuda(0))?
Dtype	tensor.to(dtype=torch.float16)	tensor.to_dtype(&DType::F16)?
Saving	torch.save({"A": A}, "model.bin")	candle::safetensors::save(&HashMap::from([("A", A)]), "model.safetensors")?
Loading	weights = torch.load("model.bin")	candle::safetensors::load("model.safetensors", &device)

Structure

• candle-core: Core ops, devices, and Tensor struct definition
• candle-nn: Tools to build real models
• candle-examples: Examples of using the library in realistic settings
• candle-kernels: CUDA custom kernels
• candle-datasets: Datasets and data loaders.
• candle-transformers: transformers-related utilities.
• candle-flash-attn: Flash attention v2 layer.

FAQ

Why should I use Candle?

Candle's core goal is to make serverless inference possible. Full machine learning frameworks like PyTorch are very large, which makes creating instances on a cluster slow. Candle allows deployment of lightweight binaries.

Secondly, Candle lets you remove Python from production workloads. Python overhead can seriously hurt performance, and the GIL is a notorious source of headaches.

Finally, Rust is cool! A lot of the HF ecosystem already has Rust crates, like safetensors and tokenizers.

Other ML frameworks

• dfdx is a formidable crate, with shapes being included in types. This prevents a lot of headaches by getting the compiler to complain about shape mismatches right off the bat. However, we found that some features still require nightly, and writing code can be a bit daunting for non rust experts.

  We're leveraging and contributing to other core crates for the runtime so hopefully both crates can benefit from each other.

• burn is a general crate that can leverage multiple backends so you can choose the best engine for your workload.

• tch-rs Bindings to the torch library in Rust. Extremely versatile, but they bring in the entire torch library into the runtime. The main contributor of tch-rs is also involved in the development of candle.

Missing symbols when compiling with the mkl feature.

If you get some missing symbols when compiling binaries/tests using the mkl features, e.g.:

  = note: /usr/bin/ld: (....o): in function `blas::sgemm':
          .../blas-0.22.0/src/lib.rs:1944: undefined reference to `sgemm_' collect2: error: ld returned 1 exit status

  = note: some `extern` functions couldn't be found; some native libraries may need to be installed or have their path specified
  = note: use the `-l` flag to specify native libraries to link
  = note: use the `cargo:rustc-link-lib` directive to specify the native libraries to link with Cargo (see https://doc.rust-lang.org/cargo/reference/build-scripts.html#cargorustc-link-libkindname)

This is likely due to a missing linker flag that was needed to enable the mkl library. You can try adding the following at the top of your binary:

extern crate intel_mkl_src;

Tracking down errors

You can set RUST_BACKTRACE=1 to be provided with backtraces when a candle error is generated.