FA-16170 / Floating-point arithmetic / Member archive

Softplus evaluates the wrong stabilized branch · case 05

Softplus evaluates the wrong stabilized branch.

Member previewVariant 5 · 3 implementations · 6 checks per implementation

Case contract

Evaluate log(1+exp(x)) without overflowing or erasing a small positive tail. 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
positive huge	`"arithmetic-error"`	`"5000"`	Failed

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This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

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