FA-16203 / Floating-point arithmetic / Member archive

Sigmoid sends large inputs to the overflowing branch · case 03

Sigmoid sends large inputs to the overflowing branch.

Member previewVariant 3 · 3 implementations · 7 checks per implementation

Case contract

Evaluate 1/(1+exp(-x)) using a stable branch for negative x. Return a nonnegative probability. Finite results are rendered to eleven significant decimal digits; modeled domain violations and arithmetic errors are explicit strings.

Why this case matters

An offline floating representation model isolates a reproducible arithmetic fault.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
negative huge	`"arithmetic-error"`	`"0"`	Failed

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