FA-17100 / Floating-point arithmetic / Member archive

Same-sign midpoint overflows its endpoint sum · case 05

Same-sign midpoint overflows its endpoint sum.

Member previewVariant 5 · 3 implementations · 9 checks per implementation

Case contract

Finite ordered binary64 midpoint rendered as hex. Opposite-sign endpoints use half-sums to avoid difference overflow; same-sign endpoints use a difference to preserve subnormal increments. Exact equal endpoints preserve their bits.

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	`"inf"`	`"0x1.640306766bac8p+1023"`	Failed

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