Hardware interview practice
Generate ordered-signature matches
Write an ordered-subsequence oracle, a legal-by-construction positive generator, and coverage points for a trace checker whose short event pattern must occur in order within a longer frame.
Reviewed example
Work through one case
Input
pattern=[3,7,3]; events=[1,3,5,7,9,3,12]Expected output
matched=1 using event positions [1,3,5]Gaps are legal in an ordered subsequence, and the repeated value 3 is consumed at two distinct increasing positions.
What to cover
Requirements
- Advance the oracle's pattern index only when an accepted event equals the next required code; an empty pattern matches every legal frame.
- Construct positive cases by choosing increasing embedding positions and filling the gaps independently.
- After deleting an occurrence or changing order to make a negative candidate, label it negative only when the oracle confirms nonmatch.
- Predict request_error and matched=0 when pattern_len exceeds 8 or event_len exceeds 32.
- Cover repeated codes, gap size, match location, and the cause used to construct a confirmed negative.