PYTHON · NUMPY

Verify before you commit

Put a certificate gate on a task policy: veto an unsafe action before it commits — a guarantee, not a score.

01Challenge

Complete the gate so it admits an action only if its next state stays in the safe envelope, else applies the safe fallback.

02Model

A robot's wrong action has physical consequences. The incumbent commit rule is an expected-value score. Energy First gates the commit: admit the policy's action only if the energy proves it stays safe — otherwise veto it for the energy-shaping fallback. The same energy is the task object, the safety barrier, and the fallback.

03Guided practice

The safe envelope is a sublevel set S = {V ≤ c}. The gate checks the ACTUAL next state under the proposed action: if V(next) ≤ c, admit; else apply the fallback (which decreases V, keeping you in S). So S is forward-invariant by construction.

04Feedback

PASS WHEN PASS when the gated loop has 0 envelope violations while the ungated policy has some.

If your run fails, check:

The gate admits an action only if its next state satisfies V ≤ c; otherwise the fallback keeps you in S.
This is a guarantee before commit — the certificate supplies what the policy's score cannot.

05Retrieve & space

Why is checking the ACTUAL next state a rigorous (discrete-time) guarantee?
What makes the fallback always safe?

06Mastery & project

Verify before you commit: the energy gate vetoes unsafe actions with a machine-checked proof, keeping the body in a certified-safe set.

Make the policy even more aggressive and confirm the gate still holds 0 violations — a guarantee independent of the policy.

← Structure, not proof Back to course →

PYTHON · NUMPY

Verify before you commit

An aggressive task policy on a pendulum sometimes commands an unsafe torque. Complete the gate; it PASSes when the gated loop never leaves the safe envelope while the ungated one does.

You read

the arrays and values already in scope

You change

the code you write in each cell

Fixed

the dataset and the checks that grade you