Publications

Journal Articles

• A.N. Letchford & M.M. Sørensen (2012) Binary positive semidefinite matrices and associated integer polytopes. Math. Program., 131(1), 253-271. (PDF)
• A.N. Letchford & S.J. Miller (2012) Fast bounding procedures for large instances of the simple plant location problem. Comp. & Oper. Res., 39(5), 985-990. (PDF)
• 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)
• 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)
• C. Feremans, M. Labbé, A.N. Letchford & J.J. Salazar (2011) On generalised network design polyhedra. Networks, 58(2), 125-136. (PDF)
• M. Fortini, A.N. Letchford, A. Lodi & K.M. Wenger (2011) Computing compatible tours for the traveling salesman problem. Math. Program. Comput., 3(1), 59-78. (PDF)
• A. Caprara, A.N. Letchford & J.J. Salazar (2011) Decorous lower bounds for minimum linear arrangement. INFORMS J. Comput., 23(1), 26-40. (PDF)
• 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)
• L. Galli & A.N. Letchford (2010) Small bipartite subgraph polytopes. Oper. Res. Lett., 38(5), 337-340. (PDF)
• K. Kaparis & A.N. Letchford (2010) Separation algorithms for 0-1 knapsack polytopes. Math. Program., 124(1-2), 69-91. (PDF)
• A. Caprara & A.N. Letchford (2010) New techniques for cost sharing in combinatorial optimization games. Math. Program., 124(1-2), 93-118. (PDF)
• S. Burer & A.N. Letchford (2009) On non-convex quadratic programming with box constraints. SIAM J. Opt., 20(2), 1073-1089. (PDF)
• 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)
• A.N. Letchford & A. Oukil (2009) Exploiting sparsity in pricing routines for the capacitated arc routing problem. Comp. & Oper. Res., 36(7), 2320-2327. (PDF)
• 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)
• A.N. Letchford & N.A. Pearson (2008) Exploiting planarity in separation routines for the symmetric traveling salesman problem. Discr. Opt., 5(2), 220-230. (PDF)
• K. Kaparis & A.N. Letchford (2008) Local and global lifted cover inequalities for the multidimensional knapsack problem. Eur. J. Opl Res., 186(1), 91–103. (PDF)
• A.N. Letchford & N.A. Pearson (2008) Good triangulations yield good tours. Comp. & Oper. Res., 35(2), 638-647. (PDF)
• A.N. Letchford, J. Lysgaard & R.W. Eglese (2007) A branch-and-cut algorithm for the capacitated open vehicle routing problem. J. Opl Res. Soc., 58(12), 1642-1651. (PDF)
• 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)
• M. Giandomenico & A.N. Letchford (2006) Exploring the relationship between max-cut and stable set relaxations. Math. Program., 106(1), 159-175. (PDF)
• A.N. Letchford & J.J. Salazar (2006) Projection results for vehicle routing. Math. Program., 105(2-3), 251-274. (PDF)
• 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) © Elsevier.
• 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) © Springer.
• A.N. Letchford & A. Lodi (2003) Primal separation algorithms. 4OR: Quart. J. of Oper. Res., 1(3), 209-224. (PDF) © Springer.
• A.N. Letchford (2003) Binary clutter inequalities for integer programs. Math. Program., 98(1-3), 201-221. (PDF) © Springer.
• A. Caprara & A.N. Letchford (2003) On the separation of split cuts and related inequalities. Math. Program., 94(2-3), 279-294. (PDF) © Springer.
• 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) © Springer.
• A.N. Letchford & A. Lodi (2002) Primal cutting plane algorithms revisited. Math. Methods of Oper. Res., 56(1), 67-81. (PDF) © Springer.
• A.N. Letchford (2002) Totally tight Chvátal-Gomory cuts. Oper. Res. Lett., 30(2), 71-73. (PDF) © Elsevier.
• A.N. Letchford & A. Lodi (2002) Strengthening Chvátal-Gomory cuts and Gomory fractional cuts. Oper. Res. Lett., 30(2), 74-82. (PDF) © Elsevier.
• A.N. Letchford (2001) On disjunctive cuts for combinatorial optimization. J. of Comb. Opt., 5(3), 299-315. (PDF) © Springer.
• A.N. Letchford & A. Amaral (2001) Analysis of upper bounds for the pallet loading problem. Eur. J. Opl Res., 132(3), 582-593. (PDF) © Elsevier.
• 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) © Springer.
• A.N. Letchford (2000) Separating a superclass of comb inequalities in planar graphs. Math. Oper. Res., 25(3), 443-454. (PDF) © INFORMS.
• A. Caprara, M. Fischetti & A.N. Letchford (2000) On the separation of maximally violated mod-k cuts. Math. Program., 87(1), 37-56. (PDF) © Springer.
• A.N. Letchford (1999) The general routing polyhedron: a unifying framework. Eur. J. Opl Res., 112(1), 122-133. (PDF) © Elsevier.
• A.N. Letchford & R.W. Eglese (1998) The rural postman problem with deadline classes. Eur. J. Opl Res., 105(3), 390-400. (PDF) © Elsevier.
• 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.
• A.N. Letchford (1997) New inequalities for the general routing problem. Eur. J. Opl Res., 96(2), 317-322. (PDF) © Elsevier.
• A.N. Letchford (1996) Allocation of school bus contracts by integer programming. J. Opl Res. Soc., 47(3), 369-372.

Articles in Books

• M. Giandomenico, A.N. Letchford, F. Rossi & S. Smriglio (2011) An new approach to the stable set problem based on ellipsoids. In O. Günlük & G.J. Woeginger (eds.) Integer Programming and Combinatorial Optimization XV. Lecture Notes in Computer Science, vol. 6655. Heidelberg: Springer. (PDF)
• K. Kaparis & A.N. Letchford (2011) Cover inequalities. In J.J. Cochran et al. (eds.) Encyclopedia of Operations Research and Management Science, Volume 2, pp. 1074-1080. New York: Wiley. (PDF)
• A.N. Letchford & A. Lodi (2011) Mathematical programming approaches to the traveling salesman problem. In J.J. Cochran et al. (eds.) Encyclopedia of Operations Research and Management Science, volume 5, pp. 3125-3132. New York: Wiley. (PDF)
• A.N. Letchford (2010) Integer quadratic quasi-polyhedra. In F. Eisenbrand & B. Shepherd (eds.) Integer Programming and Combinatorial Optimization XIV. Lecture Notes in Computer Science, vol. 6080. Berlin: Springer. (PDF)
• A.N. Letchford & M.M. Sørensen (2008) Binary positive semidefinite matrices and associated integer polytopes. In A. Lodi, A. Panconesi & G. Rinaldi (eds.) Integer Programming and Combinatorial Optimization XIII. Lecture Notes in Computer Science, vol. 5035. Berlin: Springer. (PDF)
• A.N. Letchford, G. Reinelt & D.O. Theis (2004) A faster exact separation algorithm for blossom inequalities. In G. Nemhauser & D. Bienstock (eds.) Integer Programming and Combinatorial Optimization X. Lecture Notes in Computer Science, vol. 3064. Berlin: Springer. (PDF)
• A.N. Letchford & A. Lodi (2003) An augment-and-branch-and-cut framework for mixed 0-1 programming. In M. Jünger, G. Reinelt & G. Rinaldi (eds.) Combinatorial Optimization: Eureka, You Shrink! Lecture Notes in Computer Science, vol. 2570, Berlin: Springer. (PDF) © Springer.
• A.N. Letchford & A. Lodi (2002) Polynomial-time separation of simple comb inequalities. In W.J. Cook & A.S. Schulz (eds.) Integer Programming and Combinatorial Optimization IX. Lecture Notes in Computer Science, vol. 2337, Berlin: Springer. (PDF) © Springer.
• R.W. Eglese & A.N. Letchford (2001) The general routing problem. In C.H. Floudas & P.M. Pardalos (eds.) Encyclopedia of Optimization, Vol. 2, pp. 206-207. Kluwer Academic Publishers. (PDF) Copyright now belongs to Springer.
• R.W. Eglese & A.N. Letchford (2000) Polyhedral theory for arc routing problems. In M. Dror (ed.) Arc Routing: Theory, Solutions and Applications. Kluwer Academic Publishers. (PDF) Copyright now belongs to Springer.
• A. Caprara, M. Fischetti & A.N. Letchford (1999) On the separation of maximally violated mod-k cuts. In G. Cornuéjols, R.E. Burkard & G.J. Woeginger (eds.) Integer Programming and Combinatorial Optimization VII. Lecture Notes in Computer Science, vol. 1610. Berlin: Springer. (PDF)

Editorials

• A. Clark, R.W. Eglese, A.N. Letchford & M.B. Wright (2008) Combinatorial optimisation (Editorial). Discrete Applied Math, 156(3), 289-290.
• J. Lee & A.N. Letchford (2007) Mixed integer programming (Editorial). Discrete Optimization, 4(1), 1-2.

Book Reviews

• A.N. Letchford & A. Lodi (2007) Review of “The Traveling Salesman Problem: A Computational Study”. 4OR: Quart. J. of Oper. Res., 5(4), 315-317.
• A.N. Letchford (2004) Review of “Introduction to the Theory of Cooperative Games”. J. Opl Res. Soc., 55(7), 787-788. (PDF) © Palgrave.
• A.N. Letchford (2004) Review of “The Vehicle Routing Problem”. Oper. Res. Lett., 32, 392-393. (PDF) © Elsevier.
• A.N. Letchford (2002) Review of “Approximation Algorithms”. J. Opl Res. Soc., 53(7), 807-808. (PDF) © Palgrave.
• A.N. Letchford (2000) Review of "Model Building in Mathematical Programming". J. Opl Res. Soc., 51(10), 1212-1213. (PDF) © Palgrave.
• A.N. Letchford (2000) Review of "Theory of Linear and Integer Programming". J. Opl Res. Soc., 51(7), 892-893. (PDF) © Palgrave.

Mathematical Reviews

• A.N. Letchford (2012) Review of “The Chvátal-Gomory closure of a strictly convex body”. Math. Reviews No. MR2828758.
• A.N. Letchford (2011) Review of “Orbital branching”. Math. Reviews No. MR2764343.
• A.N. Letchford (2011) Review of “On the Chvátal rank of linear relaxations of the stable set polytope”. Math. Reviews No. 2560536.
• A.N. Letchford (2011) Review of “On the dominant of the s-t cut polytope: vertices, facets and adjacency”. Math. Reviews #2679998.
• A.N. Letchford (2010) Review of “Extended formulations in combinatorial optimization”. Math. Reviews #2609619.
• A.N. Letchford (2010) Review of “Minimal inequalities for an infinite relaxation of integer programs”. Math. Reviews #2600658.
• A.N. Letchford (2010) Review of “Gear composition of stable set polytopes and G-perfection”. Math. Reviews #2573497.
• A.N. Letchford (2010) Review of “Coefficient strengthening: a tool for reformulating mixed-integer programs”. Math. Reviews #2533755.
• A.N. Letchford (2010) Review of “Applying mod-k-cuts for solving linear ordering problems”. Math. Reviews #2511722.
• A.N. Letchford (2009) Review of “MIR closures of polyhedral sets”. Math. Reviews #2520406.
• A.N. Letchford (2009) Review of “Generalized mixed integer rounding inequalities: facets for infinite group polyhedra”. Math. Reviews #2505741.
• A.N. Letchford (2009) Review of “A note on the continuous mixing set”. Math. Reviews #2469128.
• A.N. Letchford (2009) Review of “Local cuts revisited”. Math. Reviews #2437266.
• A.N. Letchford (2008) Review of “FPTAS for optimizing polynomials over the mixed-integer points of polytopes in fixed dimension”. Math. Reviews #2411399.
• A.N. Letchford (2008) Review of “Projected Chvátal-Gomory cuts for mixed integer linear programs”. Math. Reviews #2375482.
• A.N. Letchford (2008) Review of “On clique separators, nearly chordal graphs, and the maximum weight stable set problem”. Math. Reviews #2363379.
• A.N. Letchford (2008) Review of “A branch-and-cut algorithm for a resource-constrained scheduling problem”. Math. Reviews #2348000.
• A.N. Letchford (2008) Review of “New cutting-planes for the time and/or precedence-constrained ATSP and directed VRP”. Math. Reviews #2317860.
• A.N. Letchford (2007) Review of “Using critical sets to solve the maximum independent set problem”. Math. Reviews #2333324.
• A.N. Letchford (2007) Review of “Optimization with binet matrices”. Math. Reviews #2320128.
• A.N. Letchford (2007) Review of “A new min-cut max-flow ratio for multicommodity flows”. Math. Reviews #2299689.
• A.N. Letchford (2007) Review of “Using mixed-integer programming to solve power grid blackout problems”. Math. Reviews #2292489.
• A.N. Letchford (2007) Review of “Integer programming formulations for the two 4-hop constrained paths problem”. Math. Reviews #2289774.

Other

• D.D. Clarke & A.N. Letchford (1995) Rules from behaviour: the use of a computational 'rule-finder' as a tool for social psychology. B.P.S., Soc Psy Section Newsletter, 33, 4-13.

Accepted for Publication

• A.R.S. Amaral & A.N. Letchford (2011) A polyhedral approach to the single-row facility layout problem. Submitted to Math. Program. January 2011. Revised November 2011. Accepted subject to minor corrections February 2012. (uncorrected version)
• L. Galli, K. Kaparis & A.N. Letchford (2011) Gap inequalities for the max-cut problem: a cutting-plane algorithm. Extended abstract for ISCO2012. Submitted November 2011. Accepted January 2012. (PDF)
• L. Galli, K. Kaparis & A.N. Letchford (2011) Complexity results for the gap inequalities for the max-cut problem. Submitted to Oper. Res. Lett. July 2011. Published online January 2012. (PDF)
• A.N. Letchford (2011) Review of “The Linear Ordering Problem: Exact and Heuristic Methods in Combinatorial Optimization”. Submitted to Interfaces October 2011. Accepted October 2011.

Submitted

• A.N. Letchford (2012) Review of “Projecting systems of linear inequalities with binary variables”. Math. Reviews No. MR2828758. Submitted February 2012.
• A.N. Letchford & S.J. Miller (2011) An aggressive reduction scheme for the simple plant location problem. Submitted to Eur. J. Oper. Res. November 2011. (PDF)
• S. Burer & A.N. Letchford (2011) Unbounded convex sets for non-convex mixed-integer quadratic programming. Submitted to Math. Program. September 2011. (PDF)
• L. Galli & A.N. Letchford (2011) Reformulating mixed-integer quadratically constrained quadratic programs. Submitted to SIAM J. Opt. January 2011. Revision requested June 2011. (original version)

In Preparation

• A.R.S. Amaral & A.N. Letchford: Linear arrangement polytopes. (draft)
• K. Andersen, A.N. Letchford & R. Weismantel: On maximally violated cutting planes.
• T. Bektas, G. Ergodan & A.N. Letchford: Modelling fairness in exact algorithms for vehicle routing.
• S. Burer & A.N. Letchford: Non-convex mixed-integer nonlinear programming: a survey (for Surveys in OR and MS).
• F. Djeumou Fomeni & A.N. Letchford: A dynamic programming heuristic for the quadratic knapsack problem. (draft)
• K. Kaparis, A.N. Letchford & S.W. Wallace: Probabilistic metric inequalities for stochastic network loading problems.
• A.N. Letchford & S.J. Miller: On the circulant inequalities for the simple plant location problem. (draft)
• A.N. Letchford & S.D. Nasiri: Compact formulations for the Steiner TSP and related problems. (draft)
• A.N. Letchford & M.M. Sørensen: A new separation routine for the Boolean quadric and cut polytopes. (draft)

PhD Thesis:

Polyhedral Results for Some Constrained Arc-Routing Problems.

Awarded at Lancaster University on 31st January 1997. Examines integer programming formulations, valid inequalities and algorithms for four 'Arc Routing Problems'.

Last update: February 2012.

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