How statement and proof provenance work
The first chip identifies the source of the statement or construction; the second identifies the source of its local proof or verification.
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These labels describe origin, not correctness: citations and verification chips remain separate evidence.
A certified floating determinant filter returns only the exact sign
Statement
Whenever Outward-bounded floating determinant filter returns
positive or negative, the exact determinant has that same sign. An
inconclusive or nonfinite result carries no sign claim.
Facts & Assumptions
Given: A finite matrix and a completed filter evaluation satisfying the stated model and range hypotheses in Outward-bounded floating determinant filter.
Outward-bounded floating determinant filter, step 4: the filter returns positive only when , and negative only when ; otherwise it returns inconclusive. These tests compare exact dyadic rationals.
A left-to-right Leibniz determinant has an explicit forward error bound: under the filter's operation hypotheses, .
Outward-rounded operations are inclusion-isotone and enclose DAG evaluations: every exact node value of a finite expression DAG with finite operation results belongs to its computed interval enclosure.
Directed dyadic rounding encloses with explicit underflow and overflow bounds: directed upward rounding encloses each finite exact endpoint from above.
Proof
The filter's absolute-term DAG evaluates from [F2]. Its returned upper endpoint satisfies by [F3]. The definition of and [F4] give , hence .
Combining [F2] with [step 1.1] yields , so .
If the algorithm returns positive, [F1] says ; by [step 2.1], . If it returns negative, then and [step 2.1] gives . In all other cases it returns no sign.
Depends on
Used by
- A nearly cocircular quadruple has a certified lifted sign Example
- A nearly collinear dyadic triangle falls through to the exact sign Example
- The filtered exact dyadic predicate is sound and terminates Theorem
Cited to discharge well-definedness by Outward-bounded floating determinant filter.
Dependency tree · two levels
16 results within two dependency steps of this one, each drawn at its shortest distance from it. An arrow runs from a result to what uses it, so the chart reads left to right and ends at this result, which carries a heavier outline. Every node is a link to that result. Click elsewhere on the chart to enlarge it.
Sources
- Jonathan R. Shewchuk, Adaptive Precision Floating-Point Arithmetic and Fast Robust Geometric Predicates, §§4.2–4.4 (standard reference, not scraped)
- CGAL Developer Manual, Robustness Issues, §11.1 (standard reference, not scraped)