Changes from stable/2.7/Cbc/README at r1804 to stable/2.8/Cbc/README at r1902
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stable/2.8/Cbc/README
r1804 r1902 26 26 ========== 27 27 28 Release 2.8.0: 29 30 1. Introduced new secondaryStatus 8 to indicate that solving stopped due to an iteration limit. 31 32 2. Solution pool is now accessible via the command line and the CbcMain* interface. 33 34 3. New mipstart option to read an initial feasible solution from a file. Only values for discrete 35 variables need to be provided. 36 37 4. Added Proximity Search heuristic by Fischetti and Monaci (off by default): 38 The simplest way to switch it on using standalone version is "proximity on". 39 40 Proximity Search is the new "NoNeighborhood Search" 01 MIP refinement heuristic recently proposed by 41 Fischetti and Monaci (2012). The idea is to define a subMIP without additional constraints but with a 42 modified objective function intended to attract the search in the proximity of the incumbent. The approach 43 works well for 01 MIPs whose solution landscape is not too irregular (meaning the there is reasonable 44 probability of finding an improved solution by flipping a small number of binary variables), in particular 45 when it is applied to the first heuristic solutions found at the root node. 46 47 5. An implementation of ZeroHalfCuts by Alberto Caprara is now available. 48 By default, these cuts are off. To use add to your command line zerohalfCuts root (or other options) or just zero. 49 So far, they may help only on a small subset of problems and may need some tuning. 50 51 The implementation of these cuts is described in 52 G. Andreello, A. Caprara, and M. Fischetti 53 "Embedding Cuts in a Branch and Cut Framework: a Computational Study with {0,1/2}Cuts" 54 INFORMS Journal on Computing 19(2), 229238, 2007 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. To encourage the use of some of the more exotic/expensive cut generators a parameter slowcutpasses has been added. 75 The idea is that the code does these cuts just a few times  less than the more usual cuts. The default is 10. 76 The cut generators identified by "may be slow" at present are just Lift and project and ReduceAndSplit (both versions). 77 78 9. Allow initialization of random seed by user. Pseudorandom numbers are used in Cbc and Clp. In Clp they 79 are used to break ties in degenerate problems, while in Cbc heuristics such as the Feasibility Pump use them 80 to decide whether to round up or down. So if a different pseudorandom seed is given to Clp then you may get 81 a different continuous optimum and so different cuts and heuristic solutions. This can be switched on by 82 setting randomSeed for Clp and/or randomCbcSeed for Cbc. The special value of 0 tells code to use time of day 83 for initial seed. 84 85 10. Building on this idea, Andrea Lodi, Matteo Fischetti, Michele Monaci, Domenico Salvagnin, Yuji Shinano, and Andrea Tramontani 86 suggest that this idea be improved by running at the root node with multiple copies of solver, each 87 with its own different seed and then passing in the solutions and cuts so that the main solver has a richer 88 set of solutions and possibly stronger cuts. This is switched on by setting multipleRootPasses. These can also 89 be done in parallel. 90 91 11. Few changes to presolve for special variables and badly scaled problems (in CoinUtils). 92 93 12. New option extraVariables <number> which switches on a trivial reformulation that introduces extra integer variables 94 to group together variables with same cost. 95 96 13. For some problems, cut generators and general branching work better if the problem would be infeasible if the cost is too high. 97 If the new option constraintFromCutoff is set, the objective function is added as a constraint which rhs is set to the current 98 cutoff value (objective value of best known solution). 99 28 100 Release 2.7.8: 29 101 Look at https://projects.coinor.org/Cbc/changeset?old_path=%2Freleases%2F2.7.7&new_path=%2Freleases%2F2.7.8 to see all changes. … … 102 174 103 175 3. Support for BuildTools version 0.7 to incorporate recent enhancements, 104 105 176 including proper library versioning in Linux, prohibiting installation of 177 private headers, etc. 106 178 107 179 4. Updated externals to new stable versions of dependent projects.
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