Ray
In plain wordsFree software that spreads Python programs, including AI training and model serving, across many computers and graphics chips so that big jobs run in parallel.
An open-source framework for spreading Python programs, including machine-learning workloads, across many processors and machines, so that code developed on a laptop can run on a cluster. Its core offers two primitives — tasks, which are remote stateless functions, and actors, which are remote stateful objects — whose calls return futures, while a distributed scheduler places work on CPUs and GPUs across machines, a shared object store passes data between them, and fault tolerance restarts failed work. Libraries built on the core cover machine-learning stages: Ray Data for distributed data processing and batch inferencebatch inference, n.: Running an AI model over a big pile of inputs as one job rather than answering each request live, like processing a stack of forms overnight. Results come back later but cost less., Ray Train for distributed training with PyTorchPyTorch, prop. n.: The most widely used free software toolkit for building and training neural networks, especially in research; programmers write ordinary Python and it handles the calculus and the graphics chips. and other frameworks, Ray Tune for hyperparameter tuninghyperparameter tuning, n.: Trying out different settings for a model's training, such as learning speed or model size, and keeping the combination that performs best on data held back for checking., Ray Serve for model servingmodel serving, n.: Running a trained AI model as a live service, so that apps and people can send it requests and get answers back quickly, reliably and at a sensible cost., and RLlib for reinforcement learningreinforcement learning, n.: A way of teaching a computer program by trial and error: it tries actions, earns points for good results and penalties for bad ones, and gradually learns which choices pay off over time.. Ray is widely used for large-scale data preparation, reinforcement-learning post-trainingpost-training, n.: Everything done to an AI model after its initial bulk training on huge amounts of text: the extra teaching that turns a raw text predictor into a helpful, safe assistant or a careful reasoner. of language models and multi-model serving, often together with vLLMvLLM, prop. n.: A free, open-source program for running large language models on servers efficiently, so one machine can answer many more users at once. Many companies use it to host AI models..
We moved the embedding job to Ray and it ran on 64 GPUs without rewriting the processing code.
Origin
Created at the University of California, Berkeley's RISELab by Robert Nishihara, Philipp Moritz and colleagues, advised by Ion Stoica and Michael I. Jordan, and described in a 2018 OSDI paper; its creators founded the company Anyscale in 2019. Ray joined the PyTorch Foundation, part of the Linux Foundation, in October 2025.
Related
- PyTorchPyTorch, prop. n.: The most widely used free software toolkit for building and training neural networks, especially in research; programmers write ordinary Python and it handles the calculus and the graphics chips.
- distributed trainingdistributed training, n.: Training one AI model on many computer chips at once, splitting up the data or the model itself among them and keeping them in sync, so that jobs that would take a single chip thousands of years finish in weeks.
- hyperparameter tuninghyperparameter tuning, n.: Trying out different settings for a model's training, such as learning speed or model size, and keeping the combination that performs best on data held back for checking.
- model servingmodel serving, n.: Running a trained AI model as a live service, so that apps and people can send it requests and get answers back quickly, reliably and at a sensible cost.
- vLLMvLLM, prop. n.: A free, open-source program for running large language models on servers efficiently, so one machine can answer many more users at once. Many companies use it to host AI models.
- reinforcement learningreinforcement learning, n.: A way of teaching a computer program by trial and error: it tries actions, earns points for good results and penalties for bad ones, and gradually learns which choices pay off over time.
Sources
- Moritz, P., Nishihara, R. et al. (2018). Ray: A Distributed Framework for Emerging AI Applications. 13th USENIX Symposium on Operating Systems Design and Implementation (OSDI 18).
- Linux Foundation (2025). PyTorch Foundation Welcomes Ray to Deliver a Unified Open Source AI Compute Stack. Press release, October 2025. linuxfoundation.org/press/pytorch-foundation-welcomes-ray-to-deliver-a-unified-open-source-ai-compute-stack
Mentioned in
PyTorch FoundationPyTorch Foundation, prop. n.: A nonprofit group, part of the Linux Foundation, that owns and steers the free PyTorch software for building AI so that no single company controls it. It now also looks after related projects.