fix(forge): Invariant Shrinking #6530
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brockelmore
requested review from
DaniPopes,
Evalir and
mattsse
as code owners
mds1
reviewed
Dec 6, 2023
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TODO: Add documentation in book about |
mattsse
approved these changes
Dec 10, 2023
2 tasks
This was referenced Apr 26, 2024
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Motivation
https://x.com/devdacian/status/1732065261195526515
https://x.com/devdacian/status/1731900735686685094
Our current shrinking algorithm for invariants doesn't work very well, leaving a ton of extra txs in the sequence. This improves it, making it easier for devs to understand the flow for the invariant to break.
Solution
Construct either a power set or random subsequence of function calls and run them all in parallel to see if the invariant still breaks. If the new shorter subsequence still breaks the invariant, update the global shortest sequence tracker. If we used a random subsequence (not power set), recurse and try to continue to reduce until we hit the
shrink_run_limit. If we used a power set, we are guaranteed to have hit a local minimum in sequence length after it is completed.Also adds a configuration option:
shrink_run_limit- this is the number of sequences to try. A higher number of sequences allowed will result in more simplification (up until a local or global minimum is found).