Gradient Flow: Gradient Descent With Infinitely Small Steps
An interactive live film: on the book's narrow valley in 3D, gradient descent steps crowd onto the exact gradient-flow curve as the step shrinks, zig-zag as it grows, and fly off past two over the largest curvature.
Narration
Here is a long, narrow valley: gentle along x one, and steep along x two.
The gradient flow is the curve that always heads straight downhill: d x over d t equals minus the gradient of f. Along it, f can only decrease.
The rest of the narration is in the book's Companion.
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