Function closeEnoughFloat

reference_oracle_test.go:929–962

closeEnoughFloat reports whether two float64 values agree to within a relative tolerance of ~4 ULP — used only for adversarial inputs where rounding modes may cause tiny divergences. The property-based loop above uses exact equality first; this is only the fallback.

(a, b float64)

// rounding modes may cause tiny divergences. The property-based loop above
// uses exact equality first; this is only the fallback.
func closeEnoughFloat(a, b float64) bool {
	if a == b {
		return true
	}
	const ulp = 4
	if a == 0 || b == 0 {
		// Near zero, compare absolute difference.
		d := a - b
		if d < 0 {
			d = -d
		}
		return d < 1e-300
	}
	// Relative tolerance comparison.
	diff := a - b
	if diff < 0 {
		diff = -diff
	}
	mag := a
	if mag < 0 {
		mag = -mag
	}
	mag2 := b
	if mag2 < 0 {
		mag2 = -mag2
	}
	if mag2 > mag {
		mag = mag2
	}
	if mag == 0 {
		return diff < 1e-300
	}
	return diff/mag < 1e-15*float64(ulp)
}