FA-61660 / Options payoff and settlement / Member archive

Exercise assignment allocation across short accounts: fifo assigns whole positions past the exercised count · case 05

More contracts are assigned than were exercised.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

Inputs exercised contracts (<= total short), shorts [account, qty, open sequence] and method. fifo assigns in ascending open sequence, each up to its quantity. pro-rata gives floor(exercised*qty/total) and distributes the remaining contracts one each by largest fractional remainder, ties by lower open sequence. Return sorted [account, assigned] for accounts with assignments.

Why this case matters

Option expiry, exercise and settlement engines move cash and shares; a wrong branch misstates obligations.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
regression fifo allocation cap 1	`[["B2", 5], ["C3", 3], ["D4", 5], ["E5", 2]]`	`[["B2", 2], ["C3", 3], ["D4", 5], ["E5", 2]]`	Failed

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