FA-100526 / Sparse tensor canonicalization / Open access

Sparse tensor: row gather returns the pointer end as an inclusive bound · case 01

row gather returns the pointer end as an inclusive bound.

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

ROOT CAUSE

CSR row segments use start-inclusive, end-exclusive offsets.

THE FAILURE

CSR row segments use start-inclusive, end-exclusive offsets.

Unsuccessful approach: The first offset belongs to the row; advancing it loses the first stored column.

Case contract

Return columns in the selected CSR row using its half-open pointer interval.

Why this case matters

A small offline sparse-array operation has explicit coordinate and storage semantics.

1 / The failure

Exit 1

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

N = 1
observations = []
def solve(ptr,columns,row):
    return columns[ptr[row]:ptr[row+1]+1]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('middle row',solve([0,2,2,4],[1,3,0,2],1),[])
check('nonempty',solve([0,2,4],[1,3,0,2],1),[0,2])
check('empty',solve([0,0],[],0),[])
check('last entry',solve([0,1],[N],0),[N])
check('leading empty',solve([0,0,2],[N,4],0),[])
check('second row',solve([0,1,3],[2,1,4],1),[1,4])
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
middle row	`[0]`	`[]`	Failed
nonempty	`[0, 2]`	`[0, 2]`	Passed
empty	`[]`	`[]`	Passed
last entry	`[1]`	`[1]`	Passed
leading empty	`[1]`	`[]`	Failed
second row	`[1, 4]`	`[1, 4]`	Passed

SHA-256 / f79a81b2029f47baca6e9776ce669578d2183272fd683d0883a41a2886f64419

2 / The unsuccessful fix

Exit 1

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

N = 1
observations = []
def solve(ptr,columns,row):
    return columns[ptr[row]+1:ptr[row+1]]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('middle row',solve([0,2,2,4],[1,3,0,2],1),[])
check('nonempty',solve([0,2,4],[1,3,0,2],1),[0,2])
check('empty',solve([0,0],[],0),[])
check('last entry',solve([0,1],[N],0),[N])
check('leading empty',solve([0,0,2],[N,4],0),[])
check('second row',solve([0,1,3],[2,1,4],1),[1,4])
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
middle row	`[]`	`[]`	Passed
nonempty	`[2]`	`[0, 2]`	Failed
empty	`[]`	`[]`	Passed
last entry	`[]`	`[1]`	Failed
leading empty	`[]`	`[]`	Passed
second row	`[4]`	`[1, 4]`	Failed

SHA-256 / 4bd3ac13469e0701628cc0bf894562411439d0816d30d59eb55170fe9c415efb

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

These are toy integer-valued COO or CSR contracts; they make no claim about a framework API, floating point policy, or large tensor performance. 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 2026-09-30T16:48:36.730807+00:00.

Case digest / 02ebf7a4514bb7a75254d87e4e2e29e592387c5b558c947f69c9e31f8c8551c7