Lab contract

What the thirteen labs promise to anyone who relies on them or extends them.

Promise

• Each lab is one file, standard library plus NumPy, runnable with python3 labs/labNN_name.py from the course root or ./run_all.sh from labs/.
• Each prints the measurement that backs one or more first principles and ends with OK; a false principle makes an assertion fail with a message that says what was expected.
• Seeds are fixed. Numbers printed in the modules and in FIRST-PRINCIPLES.md were produced by these files on 2026-11-05 on Python 3.14 with NumPy 2.5; small platform differences in timing lines (lab 03, lab 12) are expected, assertion thresholds leave room for them.
• No lab needs a GPU, a network connection, a key or more than a minute.

Not promised

• The labs are not the projects. They show a mechanism; the modules' projects apply it to a real system.
• Lab 03's decoder, lab 09's policy and lab 10's reader are toys. The invariants are real; the models are not.
• Lab 12's measured batch effect depends on your CPU's BLAS; the assertion asks only for a clear gap.

Extending

Copy a lab, change one variable, add one assertion, and write the paragraph. That is Project 7 (an ablation) at its smallest.