Journal Articles

Published

1. A.N. Letchford & M.M. Sørensen (2025) New facets of the clique partitioning polytope. Oper. Res. Lett., 59, article 107242. (open access link)
2. A.N. Letchford & L. Cheng (2024) On a variant of the change-making problem. Oper. Res. Lett., 57, article 107165. (open access link)
3. L. Galli A.N. Letchford (2024) On upper bounds for the multiple knapsack assignment problem. Oper. Res. Lett., 54, article 107104. (open access link)
4. F. Petropoulos et al. (2024) Operational research: methods and applications. J. Oper. Res. Soc., 75(3), 423-617. (open access link)
5. M.M. Sørensen & A.N. Letchford (2024) CP-Lib: Benchmark instances of the clique partitioning problem. Math. Program. Comput., 16(1), 93–111. (PDF)
6. K. Kaparis, A.N. Letchford & I. Mourtos (2023) On cut polytopes and graph minors. Discr. Optim., 50, article 100807. (PDF)
7. M.A. Boschetti, A.N. Letchford & V. Maniezzo (2023) Matheuristics: survey and synthesis. Int. Trans. Oper. Res., 30(6), 2840–2866. (open access link)
8. S. Cáceres Gelvez, T.H. Dang & A.N. Letchford (2023) On some lower bounds for the permutation flowshop problem. Comput. Oper. Res., 159, article 106320. (open access link)
9. O. Cruz-Mejía & A.N. Letchford (2023) A survey on exact algorithms for the maximum flow and minimum-cost flow problems. Networks, 82(2), 167–176. (open access link)
10. B. Boyaci, T.H. Dang & A.N. Letchford (2023) Fast upper and lower bounds for a large-scale real-world arc routing problem. Networks, 81(1), 107–124. (open access link)
11. B. Boyaci, T.H. Dang & A.N. Letchford (2023) Improving a constructive heuristic for the general routing problem. Networks, 81(1), 93–106. (open access link)
12. T. Dokka, A.N. Letchford & M.H. Mansoor (2022) Revisiting surrogate relaxation for the multidimensional knapsack problem. Oper. Res. Lett., 50(6), 674–678. (open access link)
13. C. Liu, A.N. Letchford & I. Svetunkov (2022) Newsvendor problems: an integrated method for estimation and optimisation. Eur. J. Oper. Res., 300(2), 590–601. (PDF)
14. F. Djeumou Fomeni, K. Kaparis & A.N. Letchford (2022) A cut-and-branch algorithm for the quadratic knapsack problem. Discr. Optim., 44(2), article 100579. (PDF)
15. K. Kaparis, A.N. Letchford & Y. Mourtos (2022) Generalised 2-circulant inequalities for the max-cut problem. Oper. Res. Lett., 50(2), 122–128. (PDF)
16. B. Boyaci, T.H. Dang & A.N. Letchford (2022) On matchings, T-joins and arc routing in road networks. Networks, 79(1), 20–31. (open access link)
17. A.N. Letchford, Q. Ni & Z. Zhong (2021) Bi-perspective functions for mixed-integer fractional programs with indicator variables. Math. Program., 190(1-2), 39–55. (open access link)
18. L. Galli & A.N. Letchford (2021) Valid inequalities for quadratic optimisation with domain constraints. Discr. Optim., 41, article 100661. (PDF)
19. L. Galli & A.N. Letchford (2021) A separation algorithm for the simple plant location problem. Oper. Res. Lett., 49(4), 610–615. (PDF)
20. A.N. Letchford & P. Ventura (2021) Strengthened clique-family inequalities for the stable set polytope. Oper. Res. Lett., 49(4), 586–589. (PDF)
21. T. Dokka, A.N. Letchford & M.H. Mansoor (2021) On the complexity of surrogate and group relaxation for integer linear programs. Oper. Res. Lett., 49(4), 530–534. (PDF)
22. B. Boyaci, T.H. Dang & A.N. Letchford (2021) Vehicle routing on road networks: how good is Euclidean approximation? Comput. Oper. Res., 129, article 105197. (PDF)
23. A.N. Letchford & A.N. Vu (2021) Facets from gadgets. Math. Program., 185(1–2), 297–314. (PDF)
24. A.N. Letchford, F. Rossi & S. Smriglio (2020) The stable set problem: clique and nodal inequalities revisited. Comput. Oper. Res., 123, article 105024. (PDF)
25. A.N. Letchford & G. Souli (2020) Lifting the knapsack cover inequalities for the knapsack polytope. Oper. Res. Lett., 48(5), 607–611. (PDF)
26. K. Kaparis, A.N. Letchford & Y. Mourtos (2020) On matroid parity and matching polytopes. Discr. Appl. Math., 284, 322–331. (PDF)
27. T. Bektas & A.N. Letchford (2020) Using ℓ^p norms for fairness in combinatorial optimisation. Comput. Oper. Res., 120, article 104975. (PDF)
28. A.N. Letchford & G. Souli (2020) Valid inequalities for mixed-integer programmes with fixed charges on sets of variables. Oper. Res. Lett., 48(3), 240–244. (PDF)
29. K. Glazebrook, J.A. Grant, D.S. Leslie, R. Szechtman & A.N. Letchford (2020) Adaptive policies for perimeter surveillance problems. Eur. J. Oper. Res., 283(1), 265–278. (open access link)
30. A.N. Letchford, Q. Ni & Z. Zhong (2020) A heuristic for fair dynamic resource allocation in overloaded OFDMA systems. J. of Heuristics, 26(1), 21–32. (PDF)
31. A.N. Letchford & G. Souli (2019) New valid inequalities for the fixed-charge and single-node flow polytopes. Oper. Res. Lett., 47(5), 353–357. (PDF) © Elsevier.
32. P. Fearnhead, R. Maidstone & A.N. Letchford (2019) Detecting changes in slope with an L₀ penalty. J. Comput. Graph. Stat., 28(2), 265–275. (open access link)
33. A.N. Letchford & G. Souli (2019) On lifted cover inequalities: a new lifting procedure with unusual properties. Oper. Res. Lett., 47(2), 83–87. (PDF) © Elsevier.
34. A.N. Letchford & J.J. Salazar (2019) The capacitated vehicle routing problem: stronger bounds in pseudo-polynomial time. Eur. J. Oper. Res., 272(1), 24–31. (PDF) © Elsevier.
35. A.N. Letchford & A.J. Parkes (2018) A guide to conic optimisation and its applications. RAIRO-OR, 52(4), 1087–1106. (PDF) © EDP Sciences.
36. L. Galli & A.N. Letchford (2018) A binarisation heuristic for non-convex quadratic programming with box constraints. Oper. Res. Lett., 46(5), 529–533. (PDF) © Elsevier.
37. K. Kaparis & A.N. Letchford (2018) A note on the 2-circulant inequalities for the max-cut problem. Oper. Res. Lett., 46(4), 443–447. (PDF) © Elsevier.
38. L. Galli, A.N. Letchford & S.J. Miller (2018) New valid inequalities and facets for the simple plant location problem. Eur. J. Oper. Res., 269(3), 824–833. (PDF) © Elsevier.
39. J. Fairbrother, A.N. Letchford & K. Briggs (2018) A two-level graph partitioning problem arising in mobile wireless communications. Comput. Optim. Appl., 69(3), 653–676. (PDF) © Springer.
40. J. Fairbrother & A.N. Letchford (2017) Projection results for the k-partition problem. Discr. Optim., 26, 97–111. (PDF)
41. A.N. Letchford & D.J. Grainger (2017) A note on representations of linear inequalities in non-convex mixed-integer quadratic programs. Oper. Res. Lett., 45(6), 631–634. (PDF)
42. A.N. Letchford, Q. Ni & Z. Zhong (2017) An exact algorithm for a resource allocation problem in mobile wireless communications. Comput. Optim. Appl., 68(2), 193–208. (PDF)
43. L. Galli & A.N. Letchford (2017) On the Lovász theta function and some variants. Discr. Optim., 25, 159–174. (PDF)
44. A.N. Letchford & J.J. Salazar (2016) Stronger multi-commodity flow formulations of the (capacitated) sequential ordering problem. Eur. J. Oper. Res., 251(1), 74–84. (PDF)
45. M. Giandomenico, A.N. Letchford, F. Rossi & S. Smriglio (2015) Ellipsoidal relaxations of the stable set problem: theory and algorithms. SIAM J. Optim., 25(3), 1944–1963. (PDF)
46. F. Djeumou Fomeni, K. Kaparis & A.N. Letchford (2015) Cutting planes for RLT relaxations of mixed 0-1 polynomial programs. Math. Program., 151(2), 639–658. (PDF)
47. A.N. Letchford & S.D. Nasiri (2015) The Steiner travelling salesman problem with correlated costs. Eur. J. Oper. Res., 245(1), 62–69. (PDF)
48. A.N. Letchford & J.J. Salazar (2015) Stronger multi-commodity flow formulations of the capacitated vehicle routing problem. Eur. J. Oper. Res., 244(3), 730–738. (PDF)
49. I. Aliev & A.N. Letchford (2014) Iterated Chvátal-Gomory cuts and the geometry of numbers. SIAM J. Optim., 24(3), 1294–1312. (PDF)
50. A.N. Letchford & M.M. Sørensen (2014) A new separation algorithm for the Boolean quadric and cut polytopes. Discr. Optim., 14, 61–71. (PDF)
51. A.N. Letchford, S.D. Nasiri & A. Oukil (2014) Pricing routines for vehicle routing with time windows on road networks. Comput. Oper. Res., 51, 331–337. (PDF)
52. L. Galli & A.N. Letchford (2014) A compact variant of the QCR method for quadratically constrained quadratic 0-1 programs. Optim. Lett., 8(4), 1213–1224. (PDF)
53. F. Djeumou Fomeni & A.N. Letchford (2014) A dynamic programming heuristic for the quadratic knapsack problem. INFORMS J. Comput., 26(1), 173–182. (PDF)
54. A.N. Letchford & S.J. Miller (2014) An aggressive reduction scheme for the simple plant location problem. Eur. J. Oper. Res., 234(3), 674–682. (PDF)
55. S. Burer & A.N. Letchford (2014) Unbounded convex sets for non-convex mixed-integer quadratic programming. Math. Program., 143(1–2), 231–256. (PDF)
56. A.R.S. Amaral & A.N. Letchford (2013) A polyhedral approach to the single-row facility layout problem. Math. Program., 141(1–2), 453–477. (PDF)
57. A.N. Letchford, S.D. Nasiri & D.O. Theis (2013) Compact formulations of the Steiner TSP and related problems. Eur. J. Oper. Res., 228(1), 83–92. (PDF)
58. S. Burer & A.N. Letchford (2012) Non-convex mixed-integer nonlinear programming: a survey. Surveys in Oper. Res. and Mgmt. Sci., 17(2), 97–106. (PDF)
59. L. Galli, K. Kaparis & A.N. Letchford (2012) Complexity results for the gap inequalities for the max-cut problem. Oper. Res. Lett., 40(3), 149–152. (PDF)
60. A.N. Letchford & M.M. Sørensen (2012) Binary positive semidefinite matrices and associated integer polytopes. Math. Program., 131(1–2), 253–271. (PDF)
61. A.N. Letchford & S.J. Miller (2012) Fast bounding procedures for large instances of the simple plant location problem. Comput. Oper. Res., 39(5), 985–990. (PDF)
62. A.N. Letchford, S. Pokutta & A.S. Schulz (2011) On the membership problem for the {0, 1/2}-closure. Oper. Res. Lett., 39(5), 301–304. (PDF)
63. L. Galli, K. Kaparis & A.N. Letchford (2011) Gap inequalities for non-convex mixed-integer quadratic programs. Oper. Res. Lett., 39(5), 297–300. (PDF)
64. C. Feremans, M. Labbé, A.N. Letchford & J.J. Salazar (2011) Generalised network design polyhedra. Networks, 58(2), 125–136. (PDF)
65. M. Fortini, A.N. Letchford, A. Lodi & K.M. Wenger (2011) Computing compatible tours for the symmetric traveling salesman problem. Math. Program. Comput., 3(1), 59–78. (PDF)
66. A. Caprara, A.N. Letchford & J.J. Salazar (2011) Decorous lower bounds for minimum linear arrangement. INFORMS J. Comput., 23(1), 26–40. (PDF)
67. A.N. Letchford, G. Reinelt, H. Seitz & D.O. Theis (2010) On a class of metrics related to graph layout problems. Lin. Alg. Appl., 433(11–12), 1760–1777. (PDF)
68. L. Galli & A.N. Letchford (2010) Small bipartite subgraph polytopes. Oper. Res. Lett., 38(5), 337–340. (PDF)
69. K. Kaparis & A.N. Letchford (2010) Separation algorithms for 0-1 knapsack polytopes. Math. Program., 124(1–2), 69–91. (PDF)
70. A. Caprara & A.N. Letchford (2010) New techniques for cost sharing in combinatorial optimization games. Math. Program., 124(1–2), 93–118. (PDF)
71. S. Burer & A.N. Letchford (2009) On non-convex quadratic programming with box constraints. SIAM J. Optim., 20(2), 1073–1089. (PDF)
72. M. Giandomenico, A.N. Letchford, F. Rossi & S. Smriglio (2009) An application of the Lovász-Schrijver M(K,K) operator to the stable set problem. Math. Program., 120(2), 381–401. (PDF)
73. A.N. Letchford & A. Oukil (2009) Exploiting sparsity in pricing routines for the capacitated arc routing problem. Comput. Oper. Res., 36(7), 2320–2327. (PDF)
74. A.N. Letchford, G. Reinelt & D.O. Theis (2008) Odd minimum cut-sets and b-matchings revisited. SIAM J. Discr. Math., 22(4), 1480–1487. (PDF)
75. A.N. Letchford & N.A. Pearson (2008) Exploiting planarity in separation routines for the symmetric traveling salesman problem. Discr. Optim., 5(2), 220–230. (PDF)
76. K. Kaparis & A.N. Letchford (2008) Local and global lifted cover inequalities for the multidimensional knapsack problem. Eur. J. Oper. Res., 186(1), 91–103. (PDF)
77. A.N. Letchford & N.A. Pearson (2008) Good triangulations yield good tours. Comput. Oper. Res., 35(2), 638–647. (PDF)
78. A.N. Letchford, J. Lysgaard & R.W. Eglese (2007) A branch-and-cut algorithm for the capacitated open vehicle routing problem. J. Oper. Res. Soc., 58(12), 1642–1651. (PDF)
79. L.K. Fleischer, A.N. Letchford & A. Lodi (2006) Polynomial-time separation of a superclass of simple comb inequalities. Math. Oper. Res., 31(4), 696–713. (PDF)
80. M. Giandomenico & A.N. Letchford (2006) Exploring the relationship between max-cut and stable set relaxations. Math. Program., 106(1), 159–175. (PDF)
81. A.N. Letchford & J.J. Salazar (2006) Projection results for vehicle routing. Math. Program., 105(2–3), 251–274. (PDF)
82. A.N. Letchford & N.A. Pearson (2005) A fast algorithm for minimum weight odd circuits and cuts in planar graphs. Oper. Res. Lett., 33(6), 625–628. (PDF)
83. J. Lysgaard, A.N. Letchford & R.W. Eglese (2004) A new branch-and-cut algorithm for the capacitated vehicle routing problem. Math. Program., 100(2), 423–445. (PDF)
84. A.N. Letchford & A. Lodi (2003) Primal separation algorithms. 4OR, 1(3), 209–224. (PDF)
85. A.N. Letchford (2003) Binary clutter inequalities for integer programs. Math. Program., 98(1–3), 201–221. (PDF)
86. A. Caprara & A.N. Letchford (2003) On the separation of split cuts and related inequalities. Math. Program., 94(2–3), 279–294. (PDF)
87. A.N. Letchford, R.W. Eglese & J. Lysgaard (2002) Multistars, partial multistars and the capacitated vehicle routing problem. Math. Program., 94(1), 21–40. (PDF)
88. A.N. Letchford & A. Lodi (2002) Primal cutting plane algorithms revisited. Math. Meth. Oper. Res., 56(1), 67–81. (PDF)
89. A.N. Letchford (2002) Totally tight Chvátal-Gomory cuts. Oper. Res. Lett., 30(2), 71–73. (PDF)
90. A.N. Letchford & A. Lodi (2002) Strengthening Chvátal-Gomory cuts and Gomory fractional cuts Oper. Res. Lett., 30(2), 74–82. (PDF)
91. A.N. Letchford (2001) On disjunctive cuts for combinatorial optimization. J. Comb. Optim., 5(3), 299–315. (PDF)
92. A.N. Letchford & A. Amaral (2001) Analysis of upper bounds for the pallet loading problem. Eur. J. Oper. Res., 132(3), 582–593. (PDF)
93. A. Corberán, A.N. Letchford & J.M. Sanchis (2001) A cutting plane algorithm for the general routing problem. Math. Program., 90(2), 291–316. (PDF)
94. A.N. Letchford (2000) Separating a superclass of comb inequalities in planar graphs. Math. Oper. Res., 25(3), 443–454. (PDF)
95. A. Caprara, M. Fischetti & A.N. Letchford (2000) On the separation of maximally violated mod-k cuts. Math. Program., 87(1), 37–56. (PDF)
96. A.N. Letchford (1999) The general routing polyhedron: a unifying framework. Eur. J. Oper. Res., 112(1), 122–133. (PDF)
97. A.N. Letchford & R.W. Eglese (1998) The rural postman problem with deadline classes. Eur. J. Oper. Res., 105(3), 390–400. (PDF)
98. D.D. Clarke & A.N. Letchford (1998) Action rules extracted by machine induction from feature-coded self-reports. J. Soc. Beh. Pers., 13(1), 33–50. (PDF)
99. A.N. Letchford (1997) New inequalities for the general routing problem. Eur. J. Oper. Res., 96(2), 317–322. (PDF)
100. A.N. Letchford (1996) Allocation of school bus contracts by integer programming. J. Oper. Res. Soc., 47(3), 369–372. (PDF)

Accepted

• With L. Galli: On a hierarchy of polytopes for integer quadratic programming. Accepted (May 2025) to appear in M. Barbato, N. Bianchessi & A. Boggio Tomasaz (eds) Mathematics, Algorithms and the Art and Science of Decision-Making.

Under Revision

• With S. Cáceres Gelvez & T.H. Dang: MIP-based local search for permutation flowshop scheduling with makespan objective. Submitted to Comput. Oper. Res. February 2025. Revision invited May 2025.

Submitted

• With L. Durrell & T.H. Dang: Improving the semi-Lagrangian relaxation approach to the simple plant location problem. Submitted to Comput. Oper. Res. January 2025.

Last update: May 2025.

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