FA-10756 / Raster memory layout / Open access

Overlapping row copy snapshot · case 01

Overlapping source pixels are overwritten before they are read.

Verified by executionVariant 1 · 4 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Overlapping source pixels are overwritten before they are read.

VERIFIED REPAIR

Use the stage contract: Copy count pixels between valid possibly overlapping subranges of one row using source snapshot semantics; row length is unchanged.

Unsuccessful approach: Swapping source and destination copies in the wrong direction.

Case contract

Copy count pixels between valid possibly overlapping subranges of one row using source snapshot semantics; row length is unchanged.

Why this case matters

A deterministic software graphics stage with explicit channel and coordinate conventions; no hardware, device profile or API behavior is inferred.

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(row, source, destination, count):
    out=list(row)
    for i in range(count): out[destination+i]=out[source+i]
    return out
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve(*([1, 2, 3, 4], 0, 1, 3)), [1, 1, 2, 3])
check('fixture 2', solve(*([1, 2, 3, 4], 1, 0, 3)), [2, 3, 4, 4])
check('fixture 3', solve(*([1, 2], 0, 0, 2)), [1, 2])
check('fixture 4', solve(*([1, 2], 0, 1, 0)), [1, 2])
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
fixture 1	`[1, 1, 1, 1]`	`[1, 1, 2, 3]`	Failed
fixture 2	`[2, 3, 4, 4]`	`[2, 3, 4, 4]`	Passed
fixture 3	`[1, 2]`	`[1, 2]`	Passed
fixture 4	`[1, 2]`	`[1, 2]`	Passed

SHA-256 / 9563bfe6b1cbb3c097b47f0fe62655492c376e760beffa276dbe14924fe20f20

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(row, source, destination, count):
    return list(row[:source])+list(row[destination:destination+count])+list(row[source+count:])
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve(*([1, 2, 3, 4], 0, 1, 3)), [1, 1, 2, 3])
check('fixture 2', solve(*([1, 2, 3, 4], 1, 0, 3)), [2, 3, 4, 4])
check('fixture 3', solve(*([1, 2], 0, 0, 2)), [1, 2])
check('fixture 4', solve(*([1, 2], 0, 1, 0)), [1, 2])
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
fixture 1	`[2, 3, 4, 4]`	`[1, 1, 2, 3]`	Failed
fixture 2	`[1, 1, 2, 3]`	`[2, 3, 4, 4]`	Failed
fixture 3	`[1, 2]`	`[1, 2]`	Passed
fixture 4	`[1, 2]`	`[1, 2]`	Passed

SHA-256 / 01ded35e00994870b64ea91322f8385bc8a93be87a9dcabeff1f29a51969b9c0

3 / The verified repair

Exit 0

"""Failure Map reference implementation. Python standard library only."""
import json
import math
N = 1
observations = []
def solve(row, source, destination, count):
    return list(row[:destination])+list(row[source:source+count])+list(row[destination+count:])
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('fixture 1', solve(*([1, 2, 3, 4], 0, 1, 3)), [1, 1, 2, 3])
check('fixture 2', solve(*([1, 2, 3, 4], 1, 0, 3)), [2, 3, 4, 4])
check('fixture 3', solve(*([1, 2], 0, 0, 2)), [1, 2])
check('fixture 4', solve(*([1, 2], 0, 1, 0)), [1, 2])
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
fixture 1	`[1, 1, 2, 3]`	`[1, 1, 2, 3]`	Passed
fixture 2	`[2, 3, 4, 4]`	`[2, 3, 4, 4]`	Passed
fixture 3	`[1, 2]`	`[1, 2]`	Passed
fixture 4	`[1, 2]`	`[1, 2]`	Passed

SHA-256 / 88632879474deefca9e46ccef47ce3948188e4144f39f9ef393c4cfa71932c76

Verification & scope

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 2026-09-29T14:38:41.883817+00:00.

Case digest / f066c07a6923f02dc8a21cece0f81f7b05ddf743700e0842bd90eb024c40aea1