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Algorithms · Optimization · Ising encoding

Workflow scheduling by QUBO modeling

Schedule a workflow of tasks — an instance of the workflow scheduling problem, a known NP-hard class of scheduling problems — for an industrial use case, in a way that can be represented and solved by quantum, classical, and hybrid quantum-classical algorithms.

Attested & literatureUpdated

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  • Record typeLiterature reference
  • Reference implementationtask_scheduling_problem
  • Reported costNot stated by the sources read
  • Papers1

This record, used inside a worked example

This page says they develop a novel QUBO formulation — here is a concrete, runnable instance of it.

QAOA, p=1, MaxCut on a 4-cycle

4 qubits on a 4-cycle (edges 0-1, 1-2, 2-3, 3-0), one QAOA layer with gamma=pi/8, beta=3*pi/8.

q0q1q2q3Hadamard layer(4)QAOA MaxCut layer

Where it ends up

  • 010127%
  • 101027%
  • 00118%
  • 01108%
  • 12 more outcomes31%

0101 and 1010 are the two optimal cuts of a 4-cycle (alternating around the ring); at these angles measuring the register returns one of them clearly more often than any other cut.

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Record type
Literature reference
Reference implementation
task_scheduling_problem
Reported cost
Not stated by the sources read
Complexity basis
The abstract of arXiv:2205.04844, the only source read for this record, states no complexity expression, no big-O bound and no resource count for the algorithm it presents. It names the general problem class as "a known NP-hard class of scheduling problems", presented as an established fact about workflow scheduling in general, not a bound this paper proves. It also states that "the QUBO complexity depends on the input problem", naming a dependency without stating what it is: no formula, no scaling law, and no measure of QUBO size (variable count, term count) is quoted. Its comparison claim is: "We derive problem instances from an industrial use case and compare against several quantum, classical, and hybrid quantum-classical algorithms" — naming that a comparison was run but stating no outcome, no winner, and no number for any of the algorithms compared. Its closing claim is that the authors "demonstrate the effectiveness of the approach", stated without a metric, a number, or a comparison figure. The demonstration this record covers states no complexity bound of its own. The field is left empty on purpose rather than filled with a bound written from memory.
Circuit
Not supplied

References

  • Solving workflow scheduling problems with QUBO modeling

    A. I. Pakhomchik, S. Yudin, M. R. Perelshtein, A. Alekseyenko, S. Yarkoni · 2022

    Primary source: it investigates the workflow scheduling problem as a known NP-hard class, derives problem instances from an industrial use case, compares several quantum, classical, and hybrid quantum-classical algorithms against them, develops a novel QUBO representation whose complexity it shows depends on the input problem, and presents a decomposition method to mitigate that complexity. Consult it for the QUBO formulation itself, the decomposition method, the industrial instances, and the comparison's outcome, none of which the abstract states.

Attested & literature
  • Peer-reviewed paper
Method
Curation only. This record documents the algorithm a published reference implementation demonstrates, not the demonstration itself: nothing in Leona runs Qmod. The primary reference's title, authors and submission year were read from its arXiv abs page, and the complexity claim taken from a clause of that paper's abstract (The abstract of arXiv:2205.04844, the only source read for this record, states no complexity expression, no big-O bound and no resource count for the algorithm it presents. It names the general problem class as "a known NP-hard class of scheduling problems", presented as an established fact about workflow scheduling in general, not a bound this paper proves. It also states that "the QUBO complexity depends on the input problem", naming a dependency without stating what it is: no formula, no scaling law, and no measure of QUBO size (variable count, term count) is quoted. Its comparison claim is: "We derive problem instances from an industrial use case and compare against several quantum, classical, and hybrid quantum-classical algorithms" — naming that a comparison was run but stating no outcome, no winner, and no number for any of the algorithms compared. Its closing claim is that the authors "demonstrate the effectiveness of the approach", stated without a metric, a number, or a comparison figure. The demonstration this record covers states no complexity bound of its own. The field is left empty on purpose rather than filled with a bound written from memory.). No circuit was constructed, simulated or run.
Result
Pass · the record's problem statement and primary reference agree with the sources named above.
Caveat
This is a literature record. No circuit was built, compiled, simulated or run for it, and no workflow-scheduling instance was solved here; the record documents the method as its paper states it and does not reproduce or verify the demonstration, and nothing about that demonstration's files was read for this record. The abstract calls workflow scheduling a known NP-hard class of scheduling problems; that is presented as an established fact about the problem class, not a proof this paper derives, and this record does not extend it into a claim about the hardness of the specific QUBO or decomposition the paper builds. The abstract states that the QUBO complexity depends on the input problem, without giving the dependency as a formula, an exponent, or a variable or term count for the QUBO; nothing here fills in that dependency from outside the abstract. The abstract states that a comparison was run against several quantum, classical, and hybrid quantum-classical algorithms on problem instances derived from an industrial use case, but it does not say which algorithm performed best, by how much, or on what instance sizes; this record does not supply an outcome the abstract withholds, and in particular makes no claim that any quantum or hybrid method here outperforms, or is outperformed by, any classical algorithm. The decomposition method is described only as mitigating the QUBO's complexity for this specific application, with no bound on the mitigation and no size at which it was tested, and the claim that the authors demonstrate the effectiveness of the approach is stated without a metric, so this record does not say what the demonstrated effectiveness consisted of. The abstract states no simulation and no hardware execution in so many words; deriving problem instances and comparing algorithms could have been done by any of several methods the abstract does not specify, so this record does not classify that comparison as simulated or as run on hardware beyond what the abstract itself states.
Solving workflow scheduling problems with QUBO modeling ↗
Kind
curated reference
Reviewed by
Leona Quantum curation pass
License
Citation metadata only; source publication terms apply
QUBOworkflow schedulingNP-harddecomposition methodindustrial use case

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