source: stable/2.8/Cbc/README @ 1929

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1CBC README
2==========
3
4Welcome to the README for the COIN Branch and Cut Solver (CBC). CBC is
5distributed under the Eclipse Public License and is freely redistributable.
6All source code and documentation is Copyright IBM and others. This README may
7be redistributed freely.
8
9DOCUMENTATION
10=============
11
12For a quick start guide, please see the INSTALL file in this distribution. A (somehwat outdated) user's manual is available here:
13
14http://www.coin-or.org/Cbc
15
16More up-to-date automatically generated documentation of the source code can
17be found here:
18
19http://www.coin-or.org/Doxygen/Cbc/
20
21Further information can be found here:
22
23http://projects.coin-or.org/Cbc
24
25WHAT'S NEW
26==========
27
28Release 2.8.2:
29
301. Fixed recognition of Glpk source in main configure.
31
322. Minor bugfixes in CoinUtils, Clp, and Cbc.
33
34Release 2.8.1:
35
36   Ted, please fill this in!
37
38Release 2.8.0:
39
401. Introduced new secondaryStatus 8 to indicate that solving stopped due to an iteration limit.
41
422. Solution pool is now accessible via the command line and the CbcMain* interface.
43
443. New mipstart option to read an initial feasible solution from a file. Only values for discrete
45   variables need to be provided.
46
474. Added Proximity Search heuristic by Fischetti and Monaci (off by default):
48   The simplest way to switch it on using stand-alone version is "-proximity on".
49
50   Proximity Search is the new "No-Neighborhood Search" 0-1 MIP refinement heuristic recently proposed by
51   Fischetti and Monaci (2012). The idea is to define a sub-MIP without additional constraints but with a
52   modified objective function intended to attract the search in the proximity of the incumbent. The approach
53   works well for 0-1 MIPs whose solution landscape is not too irregular (meaning the there is reasonable
54   probability of finding an improved solution by flipping a small number of binary variables), in particular
55   when it is applied to the first heuristic solutions found at the root node.
56   
575. An implementation of Zero-Half-Cuts by Alberto Caprara is now available.
58   By default, these cuts are off.  To use add to your command line -zerohalfCuts root (or other options) or just -zero.
59   So far, they may help only on a small subset of problems and may need some tuning.
60
61   The implementation of these cuts is described in
62   G. Andreello, A. Caprara, and M. Fischetti
63   "Embedding Cuts in a Branch and Cut Framework: a Computational Study with {0,1/2}-Cuts"
64   INFORMS Journal on Computing 19(2), 229-238, 2007
65   http://dx.doi.org/10.1287/ijoc.1050.0162
66
676. An alternative implementation of a reduce and split cut generator by Giacomo Nannicini is now available.
68   By default, these cuts are off.  To use add to your command line -reduce2AndSplitCuts root (or other options).
69
70   The implementation of these cuts is described in
71   G. Cornuejols and G. Nannicini
72   "Practical strategies for generating rank-1 split cuts in mixed-integer linear programming"
73   Mathematical Programming Computation 3(4), 281-318, 2011
74   http://dx.doi.org/10.1007/s12532-011-0028-6
75
767. An alternative robust implementation of a Gomory cut generator by Giacomo Nannicini is now available.
77   By default, these cuts are off.  To use add to your command line -GMI root (or other options).
78
79   The implementation of these cuts is described in
80   G. Cornuejols, F. Margot, and G. Nannicini
81   "On the safety of Gomory cut generators"
82   http://faculty.sutd.edu.sg/~nannicini/index.php?page=publications
83
848. To encourage the use of some of the more exotic/expensive cut generators a parameter -slowcutpasses has been added.
85   The idea is that the code does these cuts just a few times - less than the more usual cuts.  The default is 10.
86   The cut generators identified by "may be slow" at present are just Lift and project and ReduceAndSplit (both versions).
87   
889. Allow initialization of random seed by user.  Pseudo-random numbers are used in Cbc and Clp.  In Clp they
89   are used to break ties in degenerate problems, while in Cbc heuristics such as the Feasibility Pump use them   
90   to decide whether to round up or down.  So if a different pseudo-random seed is given to Clp then you may get
91   a different continuous optimum and so different cuts and heuristic solutions. This can be switched on by
92   setting randomSeed for Clp and/or randomCbcSeed for Cbc.  The special value of 0 tells code to use time of day
93   for initial seed.
94   
9510. Building on this idea, Andrea Lodi, Matteo Fischetti, Michele Monaci, Domenico Salvagnin, Yuji Shinano, and Andrea Tramontani
96   suggest that this idea be improved by running at the root node with multiple copies of solver, each
97   with its own different seed and then passing in the solutions and cuts so that the main solver has a richer
98   set of solutions and possibly stronger cuts.  This is switched on by setting -multipleRootPasses.  These can also
99   be done in parallel.
100 
10111. Few changes to presolve for special variables and badly scaled problems (in CoinUtils).
102
10312. New option -extraVariables <number> which switches on a trivial re-formulation that introduces extra integer variables
104    to group together variables with same cost.
105
10613. For some problems, cut generators and general branching work better if the problem would be infeasible if the cost is too high.
107    If the new option -constraintFromCutoff is set, the objective function is added as a constraint which rhs is set to the current
108    cutoff value (objective value of best known solution).
109
110Release 2.7.8:
111   Look at https://projects.coin-or.org/Cbc/changeset?old_path=%2Freleases%2F2.7.7&new_path=%2Freleases%2F2.7.8 to see all changes.
112
1131. Change message when LP simplex iteration limit is hit from "Exiting on maximum nodes"
114   to "Exiting on maximum number of iterations"
115
1162. Fix for using overlapping SOS.
117
1183. Fixes in buildsystem.
119
120Release 2.7.7:
121   Look at https://projects.coin-or.org/Cbc/changeset?old_path=%2Freleases%2F2.7.6&new_path=%2Freleases%2F2.7.7 to see all changes.
122
1231. Fix to report interruption on user event if SIGINT is received by CbcSolver.
124   model->status() should now be 5 if this event happened.
125   Added method CbcModel::sayEventHappened() to make cbc stop due to an 'user event'.
126
1272. Other minor fixes.
128
129Release 2.7.6:
130   Look at https://projects.coin-or.org/Cbc/changeset?old_path=%2Freleases%2F2.7.5&new_path=%2Freleases%2F2.7.6 to see all changes.
131
1321. Fixes to build system.
133
1342. Other minor fixes.
135
136Release 2.7.5:
137   Look at https://projects.coin-or.org/Cbc/changeset?old_path=%2Freleases%2F2.7.4&new_path=%2Freleases%2F2.7.5 to see all changes.
138
1391. Fixes to get AMPL interface working again.
140
1412. More fixes to MSVC++ files.
142
143Release 2.7.4:
144   Look at https://projects.coin-or.org/Cbc/changeset?old_path=%2Freleases%2F2.7.3&new_path=%2Freleases%2F2.7.4 to see all changes.
145
1461. Minor bugfixes.
147
148Release 2.7.3:
149   Look at https://projects.coin-or.org/Cbc/changeset?old_path=%2Freleases%2F2.7.2&new_path=%2Freleases%2F2.7.3 to see all changes.
150
1511. Minor bugfixes.
152
1532. Fixes to MSVC++ files.
154
155Release 2.7.2:
156   Look at https://projects.coin-or.org/Cbc/changeset?old_path=%2Freleases%2F2.7.1&new_path=%2Freleases%2F2.7.2 to see all changes.
157
1581. Allow row/column names for GMPL models.
159
1602. Added CbcModel::haveMultiThreadSupport() to indicate whether Cbc library has been compiled with multithread support.
161
1623. Added CbcModel::waitingForMiniBranchAndBound() to indicate whether sub-MIP heuristic is currently running.
163
1644. Cbc shell should work with readline if configured with --enable-gnu-packages.
165
1665. Support for compressed input files (.gz, .bz2) is now enabled by default.
167
1686. Fix problems with relative gap tolerance > 100% and further bugs.
169
1707. Fixes for MSVC++ Version 9 files.
171
1728. Minor fixes in buildsystem; update to BuildTools 0.7.1.
173
174Release 2.7.1:
175   Look at https://projects.coin-or.org/Cbc/changeset?old_path=%2Freleases%2F2.7.0&new_path=%2Freleases%2F2.7.1 to see all changes.
176
1771. Fixes to MSVC++ files
178
179Release 2.7.0:
180
1811. License has been changed to the EPL.
182
1832. Support for MSVC++ version 10 added.
184
1853. Support for BuildTools version 0.7 to incorporate recent enhancements,
186including proper library versioning in Linux, prohibiting installation of
187private headers, etc.
188
1894. Updated externals to new stable versions of dependent projects.
190
1915. Improvements to heuristics.
192
1936. New options for cut generation.
194
1957. Improved reporting of results.
196
1978. Improvements to documentation.
198
1999. Minor bug fixes.
200
201SUPPORT
202=======
203
2041. List Serve
205
206CBC users should use the Cbc mailing list. To subscribe, go to
207http://list.coin-or.org/mailman/listinfo/cbc
208
2093. Bug Reports
210
211Bug reports should be reported on the CBC development web site at
212
213https://projects.coin-or.org/Cbc/newticket
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