FA-12821 / Tournament pairing rules / Open access

Adjacent seed placement makes top seeds meet early · case 01

Adjacent seed placement makes top seeds meet early.

Verified by executionVariant 1 · 6 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Seed order is copied directly into adjacent match slots.

THE FAILURE

Seed order is copied directly into adjacent match slots.

Unsuccessful approach: Pairing high and low seeds protects the first round but places seeds one and two in the same half.

Case contract

Synthetic model: For size a positive power of two, start with [1] and repeatedly replace each seed s by [s,2*current_length+1-s]; add offset to each slot label.

Why this case matters

Makes the stated pairing or standings policy executable without assuming any real federation rulebook.

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(size, offset):
    return list(range(offset+1,offset+size+1))
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('one', solve(1,N), [N+1])
check('two', solve(2,N), [N+1,N+2])
check('four', solve(4,N), [N+1,N+4,N+2,N+3])
check('eight', solve(8,N), [N+1,N+8,N+4,N+5,N+2,N+7,N+3,N+6])
check('zero offset', solve(4,0), [1,4,2,3])
check('negative offset', solve(4,-N), [1-N,4-N,2-N,3-N])
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
one	`[2]`	`[2]`	Passed
two	`[2, 3]`	`[2, 3]`	Passed
four	`[2, 3, 4, 5]`	`[2, 5, 3, 4]`	Failed
eight	`[2, 3, 4, 5, 6, 7, 8, 9]`	`[2, 9, 5, 6, 3, 8, 4, 7]`	Failed
zero offset	`[1, 2, 3, 4]`	`[1, 4, 2, 3]`	Failed
negative offset	`[0, 1, 2, 3]`	`[0, 3, 1, 2]`	Failed

SHA-256 / 3badee87c98be20bd519244c5270c91c7ede7e20d33cc3cb3d7feb4d2cc0fa04

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(size, offset):
    return [offset+x for i in range(1,size//2+1) for x in (i,size+1-i)]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('one', solve(1,N), [N+1])
check('two', solve(2,N), [N+1,N+2])
check('four', solve(4,N), [N+1,N+4,N+2,N+3])
check('eight', solve(8,N), [N+1,N+8,N+4,N+5,N+2,N+7,N+3,N+6])
check('zero offset', solve(4,0), [1,4,2,3])
check('negative offset', solve(4,-N), [1-N,4-N,2-N,3-N])
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
one	`[]`	`[2]`	Failed
two	`[2, 3]`	`[2, 3]`	Passed
four	`[2, 5, 3, 4]`	`[2, 5, 3, 4]`	Passed
eight	`[2, 9, 3, 8, 4, 7, 5, 6]`	`[2, 9, 5, 6, 3, 8, 4, 7]`	Failed
zero offset	`[1, 4, 2, 3]`	`[1, 4, 2, 3]`	Passed
negative offset	`[0, 3, 1, 2]`	`[0, 3, 1, 2]`	Passed

SHA-256 / b4bb46b7a246037e020ef4942cd19e2de7bc8c972d1dce760ba06fc585c99e50

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 6 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.

Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.

Member access is invitation-based. Sign in with your invited account to inspect the repair.

Verification & scope

Controlled synthetic policy; does not implement an entire tournament system. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.

Observations recorded using Python 3.12.14 at 2026-09-29T14:39:00.522466+00:00.

Case digest / cf6ac8accfb0163a6d5187449100b2a9065805b75b95b6a15e4f949f4ea6748d