Chaubard describes diffusion as a way to learn data distributions, including in high-dimensional settings with limited examples. The basic process adds noise to training data, then teaches a model to reverse that process and recover data.
The ML Technique Every Founder Should Know
Speaker
YC visiting partner François Chaubard discusses diffusion and its applications with the host of Y Combinator’s Decoded podcast.
Chaubard traces progress through changes to noise schedules and training objectives, including predicting the data, the added error, or velocity. He explains that flow matching uses a straight path between noise and data and trains a model to predict the velocity along it. In his example, the training loop is only a few lines, though scaling the model still takes substantial engineering.
The conversation covers diffusion for images, video, proteins, weather forecasting, and robotics. Chaubard says the core procedure can stay the same across domains while the model architecture changes; examples include protein design, GenCast, and diffusion policies for robots. He also notes that changing the number of inference steps from the number used in training can fail, while distillation can produce a model for fewer steps.
Chaubard contrasts diffusion with language models that emit one token at a time, suggesting diffusion can support randomness and generation across larger chunks. He connects this to iterative revision and concept-level thinking, while presenting it as a perspective on intelligence rather than a demonstrated account of how brains work.
For teams training models, Chaubard recommends evaluating diffusion as part of the training process, including as a way to learn a latent space. For teams using models, he advises updating expectations as image generation has improved and considering applications such as robotics, proteins, DNA, and self-driving. He frames time, money, and data as important constraints on scaling these applications.
Takeaways
- For a new modeling problem, test whether adding noise and learning to reverse it fits the data and task.
- Compare data, noise, and velocity prediction objectives; flow matching may offer a simpler training loop.
- Keep the domain specific: diffusion’s core procedure can pair with different architectures and data types.
- Match inference steps to the model’s training setup; use distillation if you need fewer steps.
- When evaluating an AI product area, account for the time, money, and data needed to scale model quality.
Mentioned in this talk
Search inside this talk
What was claimed 10
- previously atFrançois Chaubard previously at Focal Systemsran the company for a decade
“After a decade running Focal Systems”
YouTube Unverified1 source· Talk
- featurediffusion models: Learns a data distribution by training a model to reverse a process that adds noise to data
“Then we flip it and teach the model to reverse that process.”
YouTube Unverified1 source· Talk
- usesnewest version uses diffusion heavily
“the newest version, has used diffusion pretty heavily”
YouTube Unverified1 source· Talk
- featureDiffDock: Predicts small-molecule binding to proteins
“works really well for predicting small-molecule binding to proteins”
YouTube Unverified1 source· Talk
- metricFID: 222 for the demonstrated generated images; modern models might score 8 or 10
“The Fréchet inception distance is 222”
YouTube Unverified1 source· Talk
- featureflow-matching models: Trains a model to predict a global velocity between noise and data
“There is a velocity, a global velocity between the noise and the data”
YouTube Unverified1 source· Talk
- metricflow-matching models: About 10 or 15 lines of code for the demonstrated procedure
“10 or 15 lines of code”
YouTube Unverified1 source· Talk
- featurediffusion models: Can be applied to image and video generation, text, code, proteins, robotic policies, and weather forecasting
“It can be used for just about anything.”
YouTube Unverified1 source· Talk













