Changeset 1884
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 Apr 6, 2013 10:08:12 AM (7 years ago)
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trunk/Cbc/README
r1853 r1884 26 26 ========== 27 27 28 Release 2.8 :28 Release 2.8.0: 29 29 30 30 1. Introduced new secondaryStatus 8 to indicate that solving stopped due to an iteration limit. … … 44 44 probability of finding an improved solution by flipping a small number of binary variables), in particular 45 45 when it is applied to the first heuristic solutions found at the root node. 46 46 47 5. An implementation of ZeroHalfCuts by Alberto Caprara is now available. 47 48 By default, these cuts are off. To use add to your command line zerohalfCuts root (or other options) or just zero. … … 49 50 50 51 The implementation of these cuts is described in 51 G. Andreello, A. Caprara, M. Fischetti52 âEmbedding Cuts in a Branch and Cut Framework: a Computational Study with {0,1/2}Cutsâ52 G. Andreello, A. Caprara, and M. Fischetti 53 "Embedding Cuts in a Branch and Cut Framework: a Computational Study with {0,1/2}Cuts" 53 54 INFORMS Journal on Computing 19(2), 229238, 2007 54 6. Allow initialization of random seed by user. Pseudorandom numbers are used in Cbc and Clp. In Clp they 55 http://dx.doi.org/10.1287/ijoc.1050.0162 56 57 6. An alternative implementation of a reduce and split cut generator by Giacomo Nannicini is now available. 58 By default, these cuts are off. To use add to your command line reduce2AndSplitCuts root (or other options). 59 60 The implementation of these cuts is described in 61 G. Cornuejols and G. Nannicini 62 "Practical strategies for generating rank1 split cuts in mixedinteger linear programming" 63 Mathematical Programming Computation 3(4), 281318, 2011 64 http://dx.doi.org/10.1007/s1253201100286 65 66 7. An alternative robust implementation of a Gomory cut generator by Giacomo Nannicini is now available. 67 By default, these cuts are off. To use add to your command line GMI root (or other options). 68 69 The implementation of these cuts is described in 70 G. Cornuejols, F. Margot, and G. Nannicini 71 "On the safety of Gomory cut generators" 72 http://faculty.sutd.edu.sg/~nannicini/index.php?page=publications 73 74 8. Allow initialization of random seed by user. Pseudorandom numbers are used in Cbc and Clp. In Clp they 55 75 are used to break ties in degenerate problems, while in Cbc heuristics such as the Feasibility Pump use them 56 76 to decide whether to round up or down. So if a different pseudorandom seed is given to Clp then you may get … … 58 78 setting randomSeed for Clp and/or randomCbcSeed for Cbc. The special value of 0 tells code to use time of day 59 79 for initial seed. 60 7. Building on this idea Andrea Lodi , Matteo Fischetti , Michele Monaci , Domenico Salvagnin and Andrea Tramontani 80 81 9. Building on this idea Andrea Lodi, Matteo Fischetti, Michele Monaci, Domenico Salvagnin and Andrea Tramontani 61 82 suggest that this idea be be improved by running at the root node with multiple copies of solver, each 62 83 with its own different seed and then passing in the solutions and cuts so that the main solver has a richer 63 84 set of solutions and possibly stronger cuts. This is switched on by setting multipleRootPasses. These can also 64 85 be done in parallel. 86 87 10. Few changes to presolve for special variables and badly scaled problems (in CoinUtils). 65 88 89 11. New option extraVariables <number> which switches on a trivial reformulation to group variables with same cost together. 66 90 67 91
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