A hybrid constraint programming and semidefinite programming approach for the stable set problem

This work presents a hybrid approach to solve the maximum stable set problem, using constraint and semidefinite programming. The approach consists of two steps: subproblem generation and subproblem solution. First we rank the variable domain values, based on the solution of a semidefinite relaxation. Using this ranking, we generate the most promising subproblems first, by exploring a search tree using a limited discrepancy strategy. Then the subproblems are being solved using a constraint programming solver. To strengthen the semidefinite relaxation, we propose to infer additional constraints from the discrepancy structure. Computational results show that the semidefinite relaxation is very informative, since solutions of good quality are found in the first subproblems, or optimality is proven immediately.Comment: 14 page

Improving backtrack search Three case studies of localized dynamic hybridization

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN034057 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Scaleability in planning

We explore the performance of three planners, viz. parcPLAN, IPP and Blackbox, on a variant of the standard blocks-world problem. The variant problem has a restricted number of table positions, and the number of arms can vary (from 1 upwards). This type of problem is typical of many real world planning problems, where resources form a signicant component. The empirical studies reveal that least commitment planning, as implemented in parcPLAN, is far more eective than the strategies in IPP and Blackbox. But the studies also reveal a serious limitation on the scaleability of parcPLAN's algorithm

Eplex: Harnessing mathematical programming solvers for constraint logic programming

Abstract. The eplex library of the ECL i PS e Constraint Logic Programming platform allows the integration of Mathematical Programming techniques with its native Constraint Logic Programming techniques within the same unified framework. It provides an interface to state-of-the-art Mathematical Programming solvers, and a set of programming primitives that allow ‘hybrid ’ techniques to be easily expressed. This paper presents these facilities, and discusses some associated implementation issues

Towards a Closer Integration of Finite Domain Propagation and Simplex-Based Algorithms

This paper describes our experience in implementing an industrial application using the Finite Domain solver of the ECL i PS e Constraint Logic Programming (CLP) system, in conjunction with the Mathematical Programming (MP) system, FortMP. In this technique, the ECL i PS e system generates a feasible solution that is adapted to construct a starting point (Basic solution) for the MP solver. The Basic solution is then used as an input to the FortMP system to warm-start the Simplex (SX) algorithm, hastening the solution of the linear programming relaxation, (LPR). SX proceeds as normal to find the optimal integer solution. Preliminary results indicate that the integration of the two environments is suitable for for this application in particular, and may generally yield significant benefits. We describe adaptations required in the hybrid method, and report encouraging experimental results for this problem. i Towards a Closer Integration of : : : ii Contents 1 Introduction and..

Dinitrogen Coordination to a High-Spin Diiron(I/II) Species

International audienceDinitrogen coordination to iron centers underpins industrial and biological fixation in the Haber-Bosch process and by the FeM cofactors in the nitrogenase enzymes. The latter employ local high-spin metal centers; however, iron-dinitrogen coordination chemistry remains dominated by low-valent states, contrasting the enzyme systems. Here, we report a high-spin mixed-valent cis-(mu-1,2-dinitrogen)diiron(I/II) complex [(FeBr)(2)(mu-N-2)L-bis](-) (2), where [L-bis](-) is a bis(beta-diketiminate) cyclophane. Field-applied Mossbauer spectra, dc and ac magnetic susceptibility measurements, and computational methods support a delocalized S=(7)/(2) Fe2N2 unit with D=-5.23 cm(-1) and consequent slow magnetic relaxation