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Clarification for the discussion in today's tutorial
Written on 04.11.2026 17:04 by Hevra Petekkaya
Hi everyone,
First of all, I've uploaded the PDF version of the slides for today's tutorial, as some of you requested.
Second, we had a discussion about two-step flow model sampling and whether we end up at the mean of the target distribution, which was 0 in our example with equally likely targets (+3 and −3).
The answer depends on the step size we take. At (t=0), the model predicts an instantaneous velocity pointing toward the mean of the target distribution. If we take a full Euler step (Delta t=1), we end up exactly at the mean, regardless of our initially sampled noise.
However, in two-step sampling, we usually take a step of size (Delta t=0.5). This means multiplying the predicted velocity by 0.5 and adding it to our current position. We therefore only move halfway toward the mean, rather than reaching it, unless our initial noise sample was already 0.
We then query the model again at (t=0.5), using our new position (z_{0.5}), to predict an updated velocity and take another step of size 0.5.
I hope this clarifies the confusion. If not, you know where and when to find us :)