REVIEW 4 major objections 6 minor 35 references
New Multi-objective Partial Optimisation Decomposition Strategies for the Thesis Defence Scheduling Problem
T0 review · 4 major / 6 minor · reviewed 2026-08-12 · deepseek-v4-flash
Pith's one-line read This paper claims that decomposing the monolithic multi-objective thesis defence scheduling problem into two sequential multi-objective submodels—genetic algorithms for committee assignment, then augmented $\epsilon$-constraint for time…
desk verdict A useful, honestly reported decomposition method for multi-objective thesis scheduling; the quality claim leans on a proxy whose weak link to one objective is acknowledged in the paper. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The central mechanism is the multi-stage decomposition with a proxy objective. The load-bearing object is $z_5(x)$, the number of time slots where all members assigned to a defence are simultaneously available (Equation 25 in the first submodel). It is meant to predict the two second-stage objectives, $z_3$ (time-slot preferences) and $z_4$ (committee days). The second stage applies the augmented $\epsilon$-constraint method (Mavrotas and Florios 2013) to each committee configuration, and the overall non-dominated set is collected across all configurations. The genetic algorithms (NSGA-II and NSGA-III) supply diverse partial solutions, while the proxy objective steers that diversity toward configurations with scheduling flexibility.
What would settle it
Take a real instance where most committee members' available slots are spread thinly across many different days, so many defences have many 'available' slots but on non-overlapping days, and run both the decomposed method and the monolithic augmented $\epsilon$-constraint with a generous time limit. If the decomposed method's non-dominated front in the committee-days objective ($z_4$) is consistently dominated by the monolithic front, the proxy's predictive power for $z_4$ is falsified.
Extended reading notes
Core claim
The discovery is a multi-objective partial optimisation decomposition strategy. The monolithic problem is broken into two sequentially solved multi-objective submodels. The first submodel uses NSGA-II or NSGA-III to find committee configurations, evaluated by workload balance ($z_1$), committee suitability ($z_2$), and a proxy objective $z_5$ that counts, for each defence, the number of time slots in which all assigned committee members are available. The second submodel takes each configuration as a partial solution and applies an augmented $\epsilon$-constraint method to optimise time-slot preference satisfaction ($z_3$) and committee days ($z_4$). The paper claims this yields substantial efficiency gains: on small instances the decomposition takes 8–32% of the monolithic time with slightly worse hypervolume; on larger instances it takes 6–18% of the time with better hypervolume; and in the case study it found more non-dominated solutions and improved the best value in all three objectives over the comparison method. The paper argues the proxy objective is what makes the decomposition viable, by transmitting information about later-stage schedule quality into the earlier committee-assignment stage.
Load-bearing premise
The whole method leans on the proxy objective $z_5$—the count of time slots where all assigned committee members are available—being a trustworthy stand-in for how well a committee configuration will score on the later scheduling objectives, especially the number of committee days; the paper itself shows this relationship is weak for $z_4$.
Editorial extensions
If this is right
- On small instances where the monolithic solver reaches optimality, the decomposition achieves the same optimisation in 8–32% of the runtime, at a small cost in hypervolume.
- On large instances where the monolithic solver cannot close the gap within its time limit, the decomposition runs in 6–18% of the time and produces non-dominated sets with higher hypervolume.
- First-stage objectives (e.g., workload balance) will typically perform better than second-stage objectives (e.g., committee days), because the decomposition gives them priority.
- The quality of second-stage objectives depends on how strongly the proxy objective predicts them; the paper shows $z_5$ predicts $z_3$ well but $z_4$ weakly.
- The method is applicable to any multi-objective problem that can be split into sequential subproblems and for which partial solutions can be scored by proxy objectives.
Reading between the lines
- Editorial inference: if the proxy-objective idea transfers, other two-stage scheduling problems—course timetabling, exam scheduling, or room allocation after staff assignment—could use a similar decomposition, with one proxy objective per downstream objective to avoid the $z_4$ weakness seen here.
- Editorial inference: the efficiency gain is large enough that the approach could support interactive re-optimisation: a decision-maker could re-run the second stage under new preference weights in minutes rather than hours.
- Editorial inference: the paper's own results suggest a testable extension—adding a second proxy specifically targeting the number of shared days across a member's committees would likely improve $z_4$ performance, since the observed failure mode is exactly the scattering of available slots across different days.
- Editorial inference: hypervolume comparisons on large instances should be read with care, because the monolithic baseline's 120-second per-iteration limit means the comparison is against a truncated solver rather than the true Pareto front; the decomposition's advantage may shrink if the baseline is given more time.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper proposes a two-stage decomposition for the multi-objective thesis defence scheduling problem. In the first stage, NSGA-II or NSGA-III generates committee configurations by optimizing workload balance, committee suitability, and a proxy objective z5 that counts time slots in which all assigned committee members are available. In the second stage, an augmented epsilon-constraint method is solved separately for each committee configuration to optimize the schedule-quality objectives z3 (time-slot preferences) and z4 (committee days). All solutions are then pooled and filtered to the non-dominated set. Experiments on four random instances (two small, two large) and one real-world case study compare this approach with a monolithic augmented epsilon-constraint method. The reported results are 8--32% of monolithic time with slightly worse hypervolume on small instances, 6--18% of monolithic time with better hypervolume on large instances, and, in the case study, 39 non-dominated solutions in 1600 seconds versus 9 in 2400 seconds.
Significance. If the empirical claims hold, the paper offers a practical way to obtain approximate non-dominated sets for thesis defence scheduling much faster than a monolithic epsilon-constraint approach, and the proxy-objective idea could transfer to other decomposable multi-objective problems. The manuscript has clear strengths: complete MILP formulations, detailed pseudocode for all algorithmic components, 30-seed experiments for the random instances, and a real-world case study. The main empirical claim is partially supported by the reported runtimes and hypervolume values, but the quality advantage is contingent on the validity of the proxy objective z5 as a predictor of the second-stage objective z4, a relationship that the paper itself shows to be weak. The hypervolume comparison also lacks several definitions needed for reproducibility.
major comments (4)
- [Sections 5.2, 8.1, 9.2, 10.4] The proxy objective z5 (Eq. 25) is the only first-stage representation of schedule quality, but the paper itself states that z5 predicts z3 well and z4 poorly (Section 10.4), and on Instance 96 longer first-stage runs degrade the final hypervolume (Section 9.2). Since the abstract's claim of better hypervolume on larger instances and the case-study improvement depend on this proxy, the quality advantage is not established as a property of the method; it is contingent on an instance-specific correlation between z5 and z4. The paper should provide a quantitative analysis of this correlation across instances, add a proxy that is informative for z4, or restrict the claim accordingly.
- [Section 9, Tables 1--4] The hypervolume comparison lacks essential definitions. The manuscript does not state which objective functions enter the hypervolume calculation (all four objectives, or only z1, z3, z4 as in the case study), what reference point is used, how negative objective values are normalized, or whether the reported times include the initialization phase described in Section 8.3. The table notes give 'Minimum hyper-volume' values, but this is not a reproducible protocol. Without these details, the claim of 'better hyper-volume indicator values' for the larger instances cannot be independently verified.
- [Section 9.1, Tables 1--2] The time comparison in Section 9.1 uses a monolithic baseline with 10 epsilon increments, whereas the decomposed second stage uses epsilon' = 1; the monolithic run with epsilon' = 1 takes 72,356 seconds and is not used as the baseline. This baseline choice should be stated explicitly in the abstract and results, and the comparison should either use the same epsilon grid for both methods or justify why different grids are appropriate. As written, the '8--32% of the time' statement could be read as comparing against a different method than the one actually used in the tables.
- [Section 9] Only two random instances are tested per size category, and only one monolithic run is reported per instance, with no variability measure for the monolithic method. The claim that the decomposition achieves better hypervolume on larger instances is therefore based on two data points. A stronger experimental design, with more instances and either multiple monolithic runs or paired statistical comparisons across seeds, is needed to support the general conclusion.
minor comments (6)
- [Eq. (16)] The quantification in Constraint (16) is ambiguous: the notation 'sum over {jt : (jt) in A_i} x_ijt <= 1, i=1..ni, j=1..nj' should be clarified to mean that for each member i and each defence j, the sum over roles t with (j,t) in A_i is at most 1.
- [Eq. (9)] In Eq. (9), the upper limit of the first summation appears to be C^m_i, but it should presumably be n_j; the right-hand side should sum the y_ijk variables over the number of defences j.
- [Eq. (28)] The augmentation term in Eq. (28) is typeset ambiguously; it should read z1(x) + (1/nz) * sum_{i=2}^{nz} (z_i(x) - zmin_i)/(zmax_i - zmin_i) to match the explanation in the text.
- [Eq. (30)] Eq. (30) uses z'_i(x) on both sides of the definition, which makes the initialization objective self-referential; the right-hand side should presumably use the original objective functions z_i(x).
- [Tables 1--4] The table headers for the decomposition results are difficult to read because values for ng = 100 and ng = 2000 are interleaved; a clearer layout with explicit column labels for each generation count would help.
- [Figures 13--14] The case-study figures plot negative objective values, but the text describes minimization objectives; a brief note in the caption explaining that the axes are transformed for maximization would prevent confusion.
Circularity Check
No significant circularity: the decomposition efficiency gain is structural, the proxy objective is an untrained heuristic rather than a fitted or self-referential quantity, and the empirical comparisons are self-contained benchmark results.
full rationale
The paper's central claims are (i) that solving the problem as two sequential multi-objective submodels is substantially faster than a monolithic augmented epsilon-constraint method, and (ii) that the resulting non-dominated sets are competitive or better in hyper-volume on larger instances. Neither claim reduces to its own inputs by construction. The speed gain follows from the smaller second-stage problem, where committees are fixed and the second-stage eligibility sets are restricted accordingly (Section 5); it is demonstrated by runtime measurements, not derived from a fitted parameter. The proxy objective z5 (Eq. 25), which counts fully available time slots per defence, is introduced as a heuristic predictor of the second-stage objectives z3 and z4 (Sections 5.2 and 8.1) and is never calibrated to those objectives, so the later comparison of z3 and z4 is not a fitted-input-called-prediction. The paper explicitly reports the proxy's weak relationship with z4 in Section 10.4, giving a concrete mechanism (a member with many available slots may still be scheduled on different days), and Section 9.2 notes that longer first stages can hurt Instance 96 because 'some relations and interactions between different assignments might not be as well represented by the proxy objective.' These are limitations of a heuristic assumption, not evidence of circularity. The self-citations to Almeida et al. (2024) are used for the problem formulation, instance generation, and the monolithic baseline implementation; the monolithic model is fully restated in Section 4, and the experimental runs are performed in this paper, so the cited prior work is not load-bearing for the claimed novelty. No uniqueness theorem or self-citation chain is invoked to force the method's design, and the hyper-volume advantage on large instances is explicitly conditioned on the 120-second-per-iteration time limit, which is a benchmarking artifact rather than a circular derivation.
Assumptions & free parameters
free parameters (7)
- GA population size ns =
200 (random instances); 136 (case study)
- Number of generations ng =
100 and 2000 (random instances); 5 (case study)
- Mutation probability m =
1%, 5%, 10%
- Crowding tournament rounds nr =
2
- Epsilon increment epsilon' =
1 or (zmax-zmin)/10
- Per-iteration time limit =
120 seconds
- Large constant M in initialisation =
not specified numerically
assumptions (5)
- domain assumption The thesis defence scheduling problem can be decomposed into two sequential stages, committee assignment and time-slot scheduling, without unacceptable loss of solution quality.
- domain assumption The number of fully available time slots (z5) is a valid proxy for the second-stage objectives z3 and z4.
- standard math The augmented epsilon-constraint method of Mavrotas and Florios (2013) yields only non-dominated solutions and can skip redundant iterations.
- domain assumption NSGA-II and NSGA-III with the specified operators adequately sample the first-stage Pareto front within the generation budget.
- domain assumption The Gurobi solver is used as an exact oracle for the MILP subproblems within the time limit.
invented entities (1)
-
Proxy objective z5 (maximise number of fully available time slots)
Cite this review
Pith. "Pith review of New Multi-objective Partial Optimisation Decomposition Strategies for the Thesis Defence Scheduling Problem." pith.science (2026). https://pith.science/paper/HAUREN76
@misc{pith2026241116297,
author = {Pith},
title = {Pith review of: New Multi-objective Partial Optimisation Decomposition Strategies for the Thesis Defence Scheduling Problem},
year = {2026},
howpublished = {\url{https://pith.science/paper/HAUREN76}},
note = {Machine review of arXiv:2411.16297}
}
read the original abstract
A new multi-objective method for the thesis defence scheduling problem is introduced. The problem involves appointing committees to defences and assigning them to a time slot and room. A multi-objective approach is necessary to provide a better understanding of possible solutions and trade-offs to decision-makers. However, this type of approach is often time-consuming. The new multi-objective optimisation approach decomposes the monolithic problem into a sequence of multi-objective problems. This leads to significant efficiency gains compared to the augmented-e constraint method. The monolithic model is decomposed into two submodels solved sequentially. In the first stage, genetic algorithms find multiple committee configurations. The performance of these solutions is assessed based on committee assignment quality objectives and a proxy objective predicting performance in the next stage. In the second stage, considering multiple partial solutions found previously, an augmented e-constraint method is solved to find non-dominated solutions regarding the assignment of time slots to defences. These solutions consider schedule quality objectives. Finally, non-dominated solutions are presented based on objective function performance for both points of view. For small-size instances, the method takes 8-32% of the time of an augmented e-constraint method but finds non-dominated sets with slightly worse hyper-volume indicator values. For larger instances, times are 6-18% of monolithic resolutions, and hyper-volume indicator values are better. A real-world case study is presented. The experiment with decomposition found 39 non-dominated solutions in 1600 seconds. The augmented e-constraint method found 9 solutions in 2400 seconds. For the three objectives, the new method found a solution improving the best-performing solution with the other method in the time limit.
Figures
Figures from the paper (10 more)
Reference graph
Works this paper leans on
-
[1]
author Almeida, J. , author Santos, D. , author Figueira, J.R. , author Francisco, A.P. , year 2024 . title A multi-objective mixed integer linear programming model for thesis defence scheduling . journal European Journal of Operational Research volume 312 , pages 92 – 116
work page 2024
-
[2]
author Battistutta, M. , author Ceschia, S. , author De Cesco, F. , author Di Gaspero, L. , author Schaerf, A. , year 2019 . title Modelling and solving the thesis defense timetabling problem . journal Journal of the Operational Research Society volume 70 , pages 1039--1050
work page 2019
-
[3]
author Bortfeldt, A. , author Yi, J. , year 2020 . title The split delivery vehicle routing problem with three-dimensional loading constraints . journal European Journal of Operational Research volume 282 , pages 545 – 558
work page 2020
-
[4]
author Bouaziz, H. , author Bardou, D. , author Berghida, M. , author Chouali, S. , author Lemouari, A. , year 2023 . title A novel hybrid multi-objective algorithm to solve the generalized cubic cell formation problem . journal Computers & Operations Research volume 150
work page 2023
-
[5]
author Bredael, D. , author Vanhoucke, M. , year 2024 . title A genetic algorithm with resource buffers for the resource-constrained multi-project scheduling problem . journal European Journal of Operational Research volume 315 , pages 19 – 34
work page 2024
-
[6]
author Burke, E.K . , author Mareček, J. , author Parkes, A.J . , author Rudová, H. , year 2010 . title Decomposition, reformulation, and diving in university course timetabling . journal Computers & Operations Research volume 37 , pages 582--597 . note Hybrid Metaheuristics
work page 2010
-
[7]
author Cacchiani, V. , author Caprara, A. , author Roberti, R. , author Toth, P. , year 2013 . title A new lower bound for curriculum-based course timetabling . journal Computers & Operations Research volume 40 , pages 2466 – 2477
work page 2013
-
[8]
author Cataldo, A. , author Ferrer, J.C. , author Miranda, J. , author Rey, P.A. , author Sauré, A. , year 2017 . title An integer programming approach to curriculum-based examination timetabling . journal Annals of Operations Research volume 258 , pages 369 – 393
work page 2017
Show all 35 references
-
[9]
, author Wicaksana, A
author Christopher, G. , author Wicaksana, A. , year 2021 . title Particle swarm optimization for solving thesis defense timetabling problem . journal TELKOMNIKA Telecommunication, Computing, Electronics and Control volume 19 , pages 762--769
2021
-
[10]
, author Gogos, C
author Dimitsas, A. , author Gogos, C. , author Pappa, E. , year 2022 . title Better solutions for the thesis defense timetabling problem using a three-phase approach . journal ACM International Conference Proceeding Series , pages 58 – 63
2022
-
[11]
, author Nickel, S
author Dunke, F. , author Nickel, S. , year 2023 . title A matheuristic for customized multi-level multi-criteria university timetabling . journal Annals of Operations Research volume 328 , pages 1313 – 1348
2023
-
[12]
author Huynh, T. T. B . , author Pham, Q. D . , author Pham, D. D . , year 2012 . title Genetic algorithm for solving the master thesis timetabling problem with multiple objectives , in: booktitle TAAI '12: Proceedings of the 2012 Conference on Technologies and Applications of...
2012
-
[13]
, author Rudová, H
author Kochaniková, B. , author Rudová, H. , year 2013 . title Student scheduling for bachelor state examinations , in: editor Kendall, G. , editor Berghe, G.V. , editor McCollum, B. (Eds.), booktitle 6th Multidisciplinary International Conference on Scheduling : Theory and Ap...
2013
-
[14]
, author Benarkah, N
author Limanto, S. , author Benarkah, N. , author Adelia, T. , year 2019 . title Thesis examination timetabling using genetic algorithm , in: editor Muliawati, T. , editor Ardiansyah, M. , editor Sari, D. , editor Permatasari, D. , editor Mu'arifin (Eds.), booktitle Internatio...
2019
-
[15]
, author Kwon, C
author Mahmoudinazlou, S. , author Kwon, C. , year 2024 a. title A hybrid genetic algorithm for the min–max multiple traveling salesman problem . journal Computers & Operations Research volume 162
2024
-
[16]
, author Kwon, C
author Mahmoudinazlou, S. , author Kwon, C. , year 2024 b. title A hybrid genetic algorithm with type-aware chromosomes for traveling salesman problems with drone . journal European Journal of Operational Research volume 318 , pages 719 – 739
2024
-
[17]
, author Florios, K
author Mavrotas, G. , author Florios, K. , year 2013 . title An improved version of the augmented e-constraint method (AUGMECON2) for finding the exact pareto set in multi-objective integer programming problems . journal Applied Mathematics and Computation volume 219 , pages 9...
2013
-
[18]
, author Figueira, J.R
author Mesquita-Cunha, M. , author Figueira, J.R. , author Barbosa-Póvoa, A.P. , year 2022 . title New -constraint methods for multi-objective integer linear programming: A pareto front representation approach . journal European Journal of Operational Research
2022
-
[19]
, author Holm, D.S
author Mikkelsen, R.O. , author Holm, D.S. , year 2022 . title A parallelized matheuristic for the international timetabling competition 2019 . journal Journal of Scheduling volume 25 , pages 429 – 452
2022
-
[20]
, author Hoang, T.A.D
author Pham, Q.D . , author Hoang, T.A.D . , author Huynh, T.T . , author Nguyen, T.H . , year 2015 . title A Java library for constraint-based local search: Application to the master thesis defense timetabling problem , in: editor Quyet Tang, H. , editor Le Anh, P. , editor D...
2015
-
[21]
, author Brunner, J.O
author Seizinger, M. , author Brunner, J.O. , year 2023 . title Optimized planning of nursing curricula in dual vocational schools focusing on the german health care system . journal European Journal of Operational Research volume 304 , pages 1223 – 1241
2023
-
[22]
, author Coelho, J
author Servranckx, T. , author Coelho, J. , author Vanhoucke, M. , year 2024 . title A genetic algorithm for the resource-constrained project scheduling problem with alternative subgraphs using a boolean satisfiability solver . journal European Journal of Operational Research ...
2024
-
[23]
, author Bulhões, T
author Soares, G. , author Bulhões, T. , author Bruck, B. , year 2024 . title An efficient hybrid genetic algorithm for the traveling salesman problem with release dates . journal European Journal of Operational Research volume 318 , pages 31 – 42
2024
-
[24]
, author Raith, A
author Stewart, R. , author Raith, A. , author Sinnen, O. , year 2023 . title Optimising makespan and energy consumption in task scheduling for parallel systems . journal Computers & Operations Research volume 154
2023
-
[25]
, author Dahms, F
author Sørensen, M. , author Dahms, F. , year 2014 . title A two-stage decomposition of high school timetabling applied to cases in denmark . journal Computers & Operations Research volume 43 , pages 36--49
2014
-
[26]
, author Suyanto , year 2020
author Tawakkal, M.I . , author Suyanto , year 2020 . title Exploration-exploitation balanced krill herd algorithm for thesis examination timetabling , in: booktitle 2020 International Conference on Data Science and Its Applications , publisher Institute of Electrical and Elec...
2020
-
[27]
, author Saraç, T
author Tutumlu, B. , author Saraç, T. , year 2023 . title A mip model and a hybrid genetic algorithm for flexible job-shop scheduling problem with job-splitting . journal Computers & Operations Research volume 155
2023
-
[28]
, author Lemmens, S
author Vermuyten, H. , author Lemmens, S. , author Marques, I. , author Beliën, J. , year 2016 . title Developing compact course timetables with optimized student flows . journal European Journal of Operational Research volume 251 , pages 651--661
2016
-
[29]
, author Wang, Y
author Wu, P. , author Wang, Y. , author Chu, C. , year 2024 . title Logic-based benders decomposition for bi-objective parallel machine selection and job scheduling with release dates and resource consumption . journal Computers & Operations Research volume 164
2024
-
[30]
, author Bai, R
author Xue, N. , author Bai, R. , author Qu, R. , author Aickelin, U. , year 2021 . title A hybrid pricing and cutting approach for the multi-shift full truckload vehicle routing problem . journal European Journal of Operational Research volume 292 , pages 500 – 514
2021
-
[31]
, author Figueira, J.R
author Zeiträg, Y. , author Figueira, J.R. , author Horta, N. , author Neves, R. , year 2022 . title Surrogate-assisted automatic evolving of dispatching rules for multi-objective dynamic job shop scheduling using genetic programming . journal Expert Systems with Applications ...
2022
-
[32]
, author Figueira, J.R
author Zeiträg, Y. , author Figueira, J.R. , author Pereira, M.A. , year 2024 . title A web-based interactive decision support system for a multi-objective lot-sizing and production scheduling model . journal International Journal of Production Economics volume 271
2024
-
[33]
, author Poon, M
author Zhao, J. , author Poon, M. , author Tan, V.Y. , author Zhang, Z. , year 2024 . title A hybrid genetic search and dynamic programming-based split algorithm for the multi-trip time-dependent vehicle routing problem . journal European Journal of Operational Research volume...
2024
-
[34]
, author Zhong, J
author Zheng, J. , author Zhong, J. , author Chen, M. , author He, K. , year 2023 . title A reinforced hybrid genetic algorithm for the traveling salesman problem . journal Computers & Operations Research volume 157
2023
-
[35]
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Reviewed August 12, 2026 · model on record in the stance chip above.
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