FA-75516 / Text diff and three-way merge / Open access
Patience diff anchors: reconstruction starts from the first pile · case 01
Only a single anchor is returned even when a long chain exists.
ROOT CAUSE
The chain is rebuilt from the top of the first pile instead of the last.
VERIFIED REPAIR
Start reconstruction from the top of the last pile.
Unsuccessful approach: Starting from the last candidate follows a chain that may be shorter than the longest one.
Case contract
Candidates are lines occurring exactly once in the old side and exactly once in the new side, as (old index, new index) pairs in old order. Keep the longest chain with increasing new index, found with patience piles (bisect on pile tops by new index, back pointers to the previous pile top) and reconstructed from the top of the last pile. Return the anchor pairs.
Why this case matters
Patience diff anchors on unique lines to produce readable diffs of code with many repeated braces and blank lines.
1 / The failure
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
import bisect
import collections
N = 1
observations = []
def solve(a, b):
ca = collections.Counter(a)
cb = collections.Counter(b)
posb = {x: j for j, x in enumerate(b)}
cand = [(i, posb[x]) for i, x in enumerate(a) if ca[x] == 1 and cb.get(x, 0) == 1]
tails = []
back = {}
for idx, (i, j) in enumerate(cand):
lo = bisect.bisect_left([cand[t][1] for t in tails], j)
if lo == len(tails):
tails.append(idx)
else:
tails[lo] = idx
back[idx] = tails[lo - 1] if lo > 0 else None
res = []
t = tails[0] if tails else None
while t is not None:
res.append(list(cand[t]))
t = back[t]
return res[::-1]
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
cases = {
1: [('unique lines in order', [['a', 'b', 'c', 'd'], ['a', 'x', 'c', 'd']], [[0, 0], [2, 2], [3, 3]]), ('crossing unique lines keep the longest chain', [['f1', 'f2', 'f3', 'g'], ['f2', 'f3', 'f1', 'g']], [[1, 0], [2, 1], [3, 3]]), ('duplicated in new side are not anchors', [['x', 'y', 'z'], ['y', 'x', 'y', 'z']], [[0, 1], [2, 3]]), ('duplicated in old side are not anchors', [['}', 'a', '}', 'b'], ['}', 'b', 'a']], [[3, 1]]), ('no unique common lines', [['r', 'r'], ['s', 's']], []), ('chain ends before the last candidate', [['u', 'v', 'w', 'p'], ['v', 'w', 'p', 'u']], [[1, 0], [2, 1], [3, 2]]), ('later short chain', [['m0', 'm1', 'm2', 'k'], ['k', 'm0', 'm1', 'm2']], [[0, 1], [1, 2], [2, 3]]), ('single candidate', [['q', 'z'], ['z', 'q', 'q']], [[1, 0]])],
2: [('unique lines in order', [['a', 'b', 'c', 'd'], ['a', 'x', 'c', 'd']], [[0, 0], [2, 2], [3, 3]]), ('crossing unique lines keep the longest chain', [['f1', 'f2', 'f3', 'g'], ['f2', 'f3', 'f1', 'g']], [[1, 0], [2, 1], [3, 3]]), ('duplicated in new side are not anchors', [['x', 'y', 'z'], ['y', 'x', 'y', 'z']], [[0, 1], [2, 3]]), ('duplicated in old side are not anchors', [['}', 'a', '}', 'b'], ['}', 'b', 'a']], [[3, 1]]), ('no unique common lines', [['r', 'r'], ['s', 's']], []), ('chain ends before the last candidate', [['u', 'v', 'w', 'p'], ['u', 'v', 'w', 'p']], [[0, 0], [1, 1], [2, 2], [3, 3]]), ('later short chain', [['m0', 'm1', 'm2', 'm3', 'k'], ['k', 'm0', 'm1', 'm2', 'm3']], [[0, 1], [1, 2], [2, 3], [3, 4]]), ('single candidate', [['q', 'z'], ['z', 'q', 'q']], [[1, 0]])],
3: [('unique lines in order', [['a', 'b', 'c', 'd'], ['a', 'x', 'c', 'd']], [[0, 0], [2, 2], [3, 3]]), ('crossing unique lines keep the longest chain', [['f1', 'f2', 'f3', 'g'], ['f2', 'f3', 'f1', 'g']], [[1, 0], [2, 1], [3, 3]]), ('duplicated in new side are not anchors', [['x', 'y', 'z'], ['y', 'x', 'y', 'z']], [[0, 1], [2, 3]]), ('duplicated in old side are not anchors', [['}', 'a', '}', 'b'], ['}', 'b', 'a']], [[3, 1]]), ('no unique common lines', [['r', 'r'], ['s', 's']], []), ('chain ends before the last candidate', [['u', 'v', 'w', 'p'], ['v', 'w', 'p', 'u']], [[1, 0], [2, 1], [3, 2]]), ('later short chain', [['m0', 'm1', 'm2', 'm3', 'm4', 'k'], ['k', 'm0', 'm1', 'm2', 'm3', 'm4']], [[0, 1], [1, 2], [2, 3], [3, 4], [4, 5]]), ('single candidate', [['q', 'z'], ['z', 'q', 'q']], [[1, 0]])],
4: [('unique lines in order', [['a', 'b', 'c', 'd'], ['a', 'x', 'c', 'd']], [[0, 0], [2, 2], [3, 3]]), ('crossing unique lines keep the longest chain', [['f1', 'f2', 'f3', 'g'], ['f2', 'f3', 'f1', 'g']], [[1, 0], [2, 1], [3, 3]]), ('duplicated in new side are not anchors', [['x', 'y', 'z'], ['y', 'x', 'y', 'z']], [[0, 1], [2, 3]]), ('duplicated in old side are not anchors', [['}', 'a', '}', 'b'], ['}', 'b', 'a']], [[3, 1]]), ('no unique common lines', [['r', 'r'], ['s', 's']], []), ('chain ends before the last candidate', [['u', 'v', 'w', 'p'], ['u', 'v', 'w', 'p']], [[0, 0], [1, 1], [2, 2], [3, 3]]), ('later short chain', [['m0', 'm1', 'm2', 'm3', 'm4', 'm5', 'k'], ['k', 'm0', 'm1', 'm2', 'm3', 'm4', 'm5']], [[0, 1], [1, 2], [2, 3], [3, 4], [4, 5], [5, 6]]), ('single candidate', [['q', 'z'], ['z', 'q', 'q']], [[1, 0]])],
5: [('unique lines in order', [['a', 'b', 'c', 'd'], ['a', 'x', 'c', 'd']], [[0, 0], [2, 2], [3, 3]]), ('crossing unique lines keep the longest chain', [['f1', 'f2', 'f3', 'g'], ['f2', 'f3', 'f1', 'g']], [[1, 0], [2, 1], [3, 3]]), ('duplicated in new side are not anchors', [['x', 'y', 'z'], ['y', 'x', 'y', 'z']], [[0, 1], [2, 3]]), ('duplicated in old side are not anchors', [['}', 'a', '}', 'b'], ['}', 'b', 'a']], [[3, 1]]), ('no unique common lines', [['r', 'r'], ['s', 's']], []), ('chain ends before the last candidate', [['u', 'v', 'w', 'p'], ['v', 'w', 'p', 'u']], [[1, 0], [2, 1], [3, 2]]), ('later short chain', [['m0', 'm1', 'm2', 'm3', 'm4', 'm5', 'm6', 'k'], ['k', 'm0', 'm1', 'm2', 'm3', 'm4', 'm5', 'm6']], [[0, 1], [1, 2], [2, 3], [3, 4], [4, 5], [5, 6], [6, 7]]), ('single candidate', [['q', 'z'], ['z', 'q', 'q']], [[1, 0]])],
}[N]
for label, args, expected in cases:
check(label, solve(*args), expected)
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 |
|---|---|---|---|
| unique lines in order | [[0, 0]] | [[0, 0], [2, 2], [3, 3]] | Failed |
| crossing unique lines keep the longest chain | [[1, 0]] | [[1, 0], [2, 1], [3, 3]] | Failed |
| duplicated in new side are not anchors | [[0, 1]] | [[0, 1], [2, 3]] | Failed |
| duplicated in old side are not anchors | [[3, 1]] | [[3, 1]] | Passed |
| no unique common lines | [] | [] | Passed |
| chain ends before the last candidate | [[1, 0]] | [[1, 0], [2, 1], [3, 2]] | Failed |
| later short chain | [[3, 0]] | [[0, 1], [1, 2], [2, 3]] | Failed |
| single candidate | [[1, 0]] | [[1, 0]] | Passed |
SHA-256 / e9bdae05ef7141a8f5dd70b3f3255c6b9680c0f73ac92b0ceae059bb746ebebe
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
import bisect
import collections
N = 1
observations = []
def solve(a, b):
ca = collections.Counter(a)
cb = collections.Counter(b)
posb = {x: j for j, x in enumerate(b)}
cand = [(i, posb[x]) for i, x in enumerate(a) if ca[x] == 1 and cb.get(x, 0) == 1]
tails = []
back = {}
for idx, (i, j) in enumerate(cand):
lo = bisect.bisect_left([cand[t][1] for t in tails], j)
if lo == len(tails):
tails.append(idx)
else:
tails[lo] = idx
back[idx] = tails[lo - 1] if lo > 0 else None
res = []
t = len(cand) - 1 if cand else None
while t is not None:
res.append(list(cand[t]))
t = back[t]
return res[::-1]
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
cases = {
1: [('unique lines in order', [['a', 'b', 'c', 'd'], ['a', 'x', 'c', 'd']], [[0, 0], [2, 2], [3, 3]]), ('crossing unique lines keep the longest chain', [['f1', 'f2', 'f3', 'g'], ['f2', 'f3', 'f1', 'g']], [[1, 0], [2, 1], [3, 3]]), ('duplicated in new side are not anchors', [['x', 'y', 'z'], ['y', 'x', 'y', 'z']], [[0, 1], [2, 3]]), ('duplicated in old side are not anchors', [['}', 'a', '}', 'b'], ['}', 'b', 'a']], [[3, 1]]), ('no unique common lines', [['r', 'r'], ['s', 's']], []), ('chain ends before the last candidate', [['u', 'v', 'w', 'p'], ['v', 'w', 'p', 'u']], [[1, 0], [2, 1], [3, 2]]), ('later short chain', [['m0', 'm1', 'm2', 'k'], ['k', 'm0', 'm1', 'm2']], [[0, 1], [1, 2], [2, 3]]), ('single candidate', [['q', 'z'], ['z', 'q', 'q']], [[1, 0]])],
2: [('unique lines in order', [['a', 'b', 'c', 'd'], ['a', 'x', 'c', 'd']], [[0, 0], [2, 2], [3, 3]]), ('crossing unique lines keep the longest chain', [['f1', 'f2', 'f3', 'g'], ['f2', 'f3', 'f1', 'g']], [[1, 0], [2, 1], [3, 3]]), ('duplicated in new side are not anchors', [['x', 'y', 'z'], ['y', 'x', 'y', 'z']], [[0, 1], [2, 3]]), ('duplicated in old side are not anchors', [['}', 'a', '}', 'b'], ['}', 'b', 'a']], [[3, 1]]), ('no unique common lines', [['r', 'r'], ['s', 's']], []), ('chain ends before the last candidate', [['u', 'v', 'w', 'p'], ['u', 'v', 'w', 'p']], [[0, 0], [1, 1], [2, 2], [3, 3]]), ('later short chain', [['m0', 'm1', 'm2', 'm3', 'k'], ['k', 'm0', 'm1', 'm2', 'm3']], [[0, 1], [1, 2], [2, 3], [3, 4]]), ('single candidate', [['q', 'z'], ['z', 'q', 'q']], [[1, 0]])],
3: [('unique lines in order', [['a', 'b', 'c', 'd'], ['a', 'x', 'c', 'd']], [[0, 0], [2, 2], [3, 3]]), ('crossing unique lines keep the longest chain', [['f1', 'f2', 'f3', 'g'], ['f2', 'f3', 'f1', 'g']], [[1, 0], [2, 1], [3, 3]]), ('duplicated in new side are not anchors', [['x', 'y', 'z'], ['y', 'x', 'y', 'z']], [[0, 1], [2, 3]]), ('duplicated in old side are not anchors', [['}', 'a', '}', 'b'], ['}', 'b', 'a']], [[3, 1]]), ('no unique common lines', [['r', 'r'], ['s', 's']], []), ('chain ends before the last candidate', [['u', 'v', 'w', 'p'], ['v', 'w', 'p', 'u']], [[1, 0], [2, 1], [3, 2]]), ('later short chain', [['m0', 'm1', 'm2', 'm3', 'm4', 'k'], ['k', 'm0', 'm1', 'm2', 'm3', 'm4']], [[0, 1], [1, 2], [2, 3], [3, 4], [4, 5]]), ('single candidate', [['q', 'z'], ['z', 'q', 'q']], [[1, 0]])],
4: [('unique lines in order', [['a', 'b', 'c', 'd'], ['a', 'x', 'c', 'd']], [[0, 0], [2, 2], [3, 3]]), ('crossing unique lines keep the longest chain', [['f1', 'f2', 'f3', 'g'], ['f2', 'f3', 'f1', 'g']], [[1, 0], [2, 1], [3, 3]]), ('duplicated in new side are not anchors', [['x', 'y', 'z'], ['y', 'x', 'y', 'z']], [[0, 1], [2, 3]]), ('duplicated in old side are not anchors', [['}', 'a', '}', 'b'], ['}', 'b', 'a']], [[3, 1]]), ('no unique common lines', [['r', 'r'], ['s', 's']], []), ('chain ends before the last candidate', [['u', 'v', 'w', 'p'], ['u', 'v', 'w', 'p']], [[0, 0], [1, 1], [2, 2], [3, 3]]), ('later short chain', [['m0', 'm1', 'm2', 'm3', 'm4', 'm5', 'k'], ['k', 'm0', 'm1', 'm2', 'm3', 'm4', 'm5']], [[0, 1], [1, 2], [2, 3], [3, 4], [4, 5], [5, 6]]), ('single candidate', [['q', 'z'], ['z', 'q', 'q']], [[1, 0]])],
5: [('unique lines in order', [['a', 'b', 'c', 'd'], ['a', 'x', 'c', 'd']], [[0, 0], [2, 2], [3, 3]]), ('crossing unique lines keep the longest chain', [['f1', 'f2', 'f3', 'g'], ['f2', 'f3', 'f1', 'g']], [[1, 0], [2, 1], [3, 3]]), ('duplicated in new side are not anchors', [['x', 'y', 'z'], ['y', 'x', 'y', 'z']], [[0, 1], [2, 3]]), ('duplicated in old side are not anchors', [['}', 'a', '}', 'b'], ['}', 'b', 'a']], [[3, 1]]), ('no unique common lines', [['r', 'r'], ['s', 's']], []), ('chain ends before the last candidate', [['u', 'v', 'w', 'p'], ['v', 'w', 'p', 'u']], [[1, 0], [2, 1], [3, 2]]), ('later short chain', [['m0', 'm1', 'm2', 'm3', 'm4', 'm5', 'm6', 'k'], ['k', 'm0', 'm1', 'm2', 'm3', 'm4', 'm5', 'm6']], [[0, 1], [1, 2], [2, 3], [3, 4], [4, 5], [5, 6], [6, 7]]), ('single candidate', [['q', 'z'], ['z', 'q', 'q']], [[1, 0]])],
}[N]
for label, args, expected in cases:
check(label, solve(*args), expected)
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 |
|---|---|---|---|
| unique lines in order | [[0, 0], [2, 2], [3, 3]] | [[0, 0], [2, 2], [3, 3]] | Passed |
| crossing unique lines keep the longest chain | [[1, 0], [2, 1], [3, 3]] | [[1, 0], [2, 1], [3, 3]] | Passed |
| duplicated in new side are not anchors | [[0, 1], [2, 3]] | [[0, 1], [2, 3]] | Passed |
| duplicated in old side are not anchors | [[3, 1]] | [[3, 1]] | Passed |
| no unique common lines | [] | [] | Passed |
| chain ends before the last candidate | [[1, 0], [2, 1], [3, 2]] | [[1, 0], [2, 1], [3, 2]] | Passed |
| later short chain | [[3, 0]] | [[0, 1], [1, 2], [2, 3]] | Failed |
| single candidate | [[1, 0]] | [[1, 0]] | Passed |
SHA-256 / 7ea2e425c9ac114f524d981a785b0710b19d0c9de16dd3ec0cb40595d5e1d784
3 / The verified repair
Exit 0"""Failure Map reference implementation. Python standard library only."""
import json
import bisect
import collections
N = 1
observations = []
def solve(a, b):
ca = collections.Counter(a)
cb = collections.Counter(b)
posb = {x: j for j, x in enumerate(b)}
cand = [(i, posb[x]) for i, x in enumerate(a) if ca[x] == 1 and cb.get(x, 0) == 1]
tails = []
back = {}
for idx, (i, j) in enumerate(cand):
lo = bisect.bisect_left([cand[t][1] for t in tails], j)
if lo == len(tails):
tails.append(idx)
else:
tails[lo] = idx
back[idx] = tails[lo - 1] if lo > 0 else None
res = []
t = tails[-1] if tails else None
while t is not None:
res.append(list(cand[t]))
t = back[t]
return res[::-1]
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
cases = {
1: [('unique lines in order', [['a', 'b', 'c', 'd'], ['a', 'x', 'c', 'd']], [[0, 0], [2, 2], [3, 3]]), ('crossing unique lines keep the longest chain', [['f1', 'f2', 'f3', 'g'], ['f2', 'f3', 'f1', 'g']], [[1, 0], [2, 1], [3, 3]]), ('duplicated in new side are not anchors', [['x', 'y', 'z'], ['y', 'x', 'y', 'z']], [[0, 1], [2, 3]]), ('duplicated in old side are not anchors', [['}', 'a', '}', 'b'], ['}', 'b', 'a']], [[3, 1]]), ('no unique common lines', [['r', 'r'], ['s', 's']], []), ('chain ends before the last candidate', [['u', 'v', 'w', 'p'], ['v', 'w', 'p', 'u']], [[1, 0], [2, 1], [3, 2]]), ('later short chain', [['m0', 'm1', 'm2', 'k'], ['k', 'm0', 'm1', 'm2']], [[0, 1], [1, 2], [2, 3]]), ('single candidate', [['q', 'z'], ['z', 'q', 'q']], [[1, 0]])],
2: [('unique lines in order', [['a', 'b', 'c', 'd'], ['a', 'x', 'c', 'd']], [[0, 0], [2, 2], [3, 3]]), ('crossing unique lines keep the longest chain', [['f1', 'f2', 'f3', 'g'], ['f2', 'f3', 'f1', 'g']], [[1, 0], [2, 1], [3, 3]]), ('duplicated in new side are not anchors', [['x', 'y', 'z'], ['y', 'x', 'y', 'z']], [[0, 1], [2, 3]]), ('duplicated in old side are not anchors', [['}', 'a', '}', 'b'], ['}', 'b', 'a']], [[3, 1]]), ('no unique common lines', [['r', 'r'], ['s', 's']], []), ('chain ends before the last candidate', [['u', 'v', 'w', 'p'], ['u', 'v', 'w', 'p']], [[0, 0], [1, 1], [2, 2], [3, 3]]), ('later short chain', [['m0', 'm1', 'm2', 'm3', 'k'], ['k', 'm0', 'm1', 'm2', 'm3']], [[0, 1], [1, 2], [2, 3], [3, 4]]), ('single candidate', [['q', 'z'], ['z', 'q', 'q']], [[1, 0]])],
3: [('unique lines in order', [['a', 'b', 'c', 'd'], ['a', 'x', 'c', 'd']], [[0, 0], [2, 2], [3, 3]]), ('crossing unique lines keep the longest chain', [['f1', 'f2', 'f3', 'g'], ['f2', 'f3', 'f1', 'g']], [[1, 0], [2, 1], [3, 3]]), ('duplicated in new side are not anchors', [['x', 'y', 'z'], ['y', 'x', 'y', 'z']], [[0, 1], [2, 3]]), ('duplicated in old side are not anchors', [['}', 'a', '}', 'b'], ['}', 'b', 'a']], [[3, 1]]), ('no unique common lines', [['r', 'r'], ['s', 's']], []), ('chain ends before the last candidate', [['u', 'v', 'w', 'p'], ['v', 'w', 'p', 'u']], [[1, 0], [2, 1], [3, 2]]), ('later short chain', [['m0', 'm1', 'm2', 'm3', 'm4', 'k'], ['k', 'm0', 'm1', 'm2', 'm3', 'm4']], [[0, 1], [1, 2], [2, 3], [3, 4], [4, 5]]), ('single candidate', [['q', 'z'], ['z', 'q', 'q']], [[1, 0]])],
4: [('unique lines in order', [['a', 'b', 'c', 'd'], ['a', 'x', 'c', 'd']], [[0, 0], [2, 2], [3, 3]]), ('crossing unique lines keep the longest chain', [['f1', 'f2', 'f3', 'g'], ['f2', 'f3', 'f1', 'g']], [[1, 0], [2, 1], [3, 3]]), ('duplicated in new side are not anchors', [['x', 'y', 'z'], ['y', 'x', 'y', 'z']], [[0, 1], [2, 3]]), ('duplicated in old side are not anchors', [['}', 'a', '}', 'b'], ['}', 'b', 'a']], [[3, 1]]), ('no unique common lines', [['r', 'r'], ['s', 's']], []), ('chain ends before the last candidate', [['u', 'v', 'w', 'p'], ['u', 'v', 'w', 'p']], [[0, 0], [1, 1], [2, 2], [3, 3]]), ('later short chain', [['m0', 'm1', 'm2', 'm3', 'm4', 'm5', 'k'], ['k', 'm0', 'm1', 'm2', 'm3', 'm4', 'm5']], [[0, 1], [1, 2], [2, 3], [3, 4], [4, 5], [5, 6]]), ('single candidate', [['q', 'z'], ['z', 'q', 'q']], [[1, 0]])],
5: [('unique lines in order', [['a', 'b', 'c', 'd'], ['a', 'x', 'c', 'd']], [[0, 0], [2, 2], [3, 3]]), ('crossing unique lines keep the longest chain', [['f1', 'f2', 'f3', 'g'], ['f2', 'f3', 'f1', 'g']], [[1, 0], [2, 1], [3, 3]]), ('duplicated in new side are not anchors', [['x', 'y', 'z'], ['y', 'x', 'y', 'z']], [[0, 1], [2, 3]]), ('duplicated in old side are not anchors', [['}', 'a', '}', 'b'], ['}', 'b', 'a']], [[3, 1]]), ('no unique common lines', [['r', 'r'], ['s', 's']], []), ('chain ends before the last candidate', [['u', 'v', 'w', 'p'], ['v', 'w', 'p', 'u']], [[1, 0], [2, 1], [3, 2]]), ('later short chain', [['m0', 'm1', 'm2', 'm3', 'm4', 'm5', 'm6', 'k'], ['k', 'm0', 'm1', 'm2', 'm3', 'm4', 'm5', 'm6']], [[0, 1], [1, 2], [2, 3], [3, 4], [4, 5], [5, 6], [6, 7]]), ('single candidate', [['q', 'z'], ['z', 'q', 'q']], [[1, 0]])],
}[N]
for label, args, expected in cases:
check(label, solve(*args), expected)
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 |
|---|---|---|---|
| unique lines in order | [[0, 0], [2, 2], [3, 3]] | [[0, 0], [2, 2], [3, 3]] | Passed |
| crossing unique lines keep the longest chain | [[1, 0], [2, 1], [3, 3]] | [[1, 0], [2, 1], [3, 3]] | Passed |
| duplicated in new side are not anchors | [[0, 1], [2, 3]] | [[0, 1], [2, 3]] | Passed |
| duplicated in old side are not anchors | [[3, 1]] | [[3, 1]] | Passed |
| no unique common lines | [] | [] | Passed |
| chain ends before the last candidate | [[1, 0], [2, 1], [3, 2]] | [[1, 0], [2, 1], [3, 2]] | Passed |
| later short chain | [[0, 1], [1, 2], [2, 3]] | [[0, 1], [1, 2], [2, 3]] | Passed |
| single candidate | [[1, 0]] | [[1, 0]] | Passed |
SHA-256 / a4ca7ad5760d347b3246a7a4dd5466be1f11bce1a8b13acf73db996373b0bb00
Verification & scope
A deterministic, bounded teaching model of one diff, patch or merge rule with stipulated conventions; it is not a production diff or version-control implementation and makes no claim of conformance to any specific tool. 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 2026-09-29T14:49:07.358301+00:00.
Case digest / c70f646883fb9110a6fc14c440ecef85947a4b7d9138440b231022ac4cb4ae57