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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 A (somehwat outdated) user's manual is available here: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
32Release 2.8.1:
33
34   Ted, please fill this in!
35
36Release 2.8.0:
37
381. Introduced new secondaryStatus 8 to indicate that solving stopped due to an iteration limit.
39
402. Solution pool is now accessible via the command line and the CbcMain* interface.
41
423. New mipstart option to read an initial feasible solution from a file. Only values for discrete
43   variables need to be provided.
44
454. Added Proximity Search heuristic by Fischetti and Monaci (off by default):
46   The simplest way to switch it on using stand-alone version is "-proximity on".
47
48   Proximity Search is the new "No-Neighborhood Search" 0-1 MIP refinement heuristic recently proposed by
49   Fischetti and Monaci (2012). The idea is to define a sub-MIP without additional constraints but with a
50   modified objective function intended to attract the search in the proximity of the incumbent. The approach
51   works well for 0-1 MIPs whose solution landscape is not too irregular (meaning the there is reasonable
52   probability of finding an improved solution by flipping a small number of binary variables), in particular
53   when it is applied to the first heuristic solutions found at the root node.
54   
555. An implementation of Zero-Half-Cuts by Alberto Caprara is now available.
56   By default, these cuts are off.  To use add to your command line -zerohalfCuts root (or other options) or just -zero.
57   So far, they may help only on a small subset of problems and may need some tuning.
58
59   The implementation of these cuts is described in
60   G. Andreello, A. Caprara, and M. Fischetti
61   "Embedding Cuts in a Branch and Cut Framework: a Computational Study with {0,1/2}-Cuts"
62   INFORMS Journal on Computing 19(2), 229-238, 2007
63   http://dx.doi.org/10.1287/ijoc.1050.0162
64
656. An alternative implementation of a reduce and split cut generator by Giacomo Nannicini is now available.
66   By default, these cuts are off.  To use add to your command line -reduce2AndSplitCuts root (or other options).
67
68   The implementation of these cuts is described in
69   G. Cornuejols and G. Nannicini
70   "Practical strategies for generating rank-1 split cuts in mixed-integer linear programming"
71   Mathematical Programming Computation 3(4), 281-318, 2011
72   http://dx.doi.org/10.1007/s12532-011-0028-6
73
747. An alternative robust implementation of a Gomory cut generator by Giacomo Nannicini is now available.
75   By default, these cuts are off.  To use add to your command line -GMI root (or other options).
76
77   The implementation of these cuts is described in
78   G. Cornuejols, F. Margot, and G. Nannicini
79   "On the safety of Gomory cut generators"
80   http://faculty.sutd.edu.sg/~nannicini/index.php?page=publications
81
828. To encourage the use of some of the more exotic/expensive cut generators a parameter -slowcutpasses has been added.
83   The idea is that the code does these cuts just a few times - less than the more usual cuts.  The default is 10.
84   The cut generators identified by "may be slow" at present are just Lift and project and ReduceAndSplit (both versions).
85   
869. Allow initialization of random seed by user.  Pseudo-random numbers are used in Cbc and Clp.  In Clp they
87   are used to break ties in degenerate problems, while in Cbc heuristics such as the Feasibility Pump use them   
88   to decide whether to round up or down.  So if a different pseudo-random seed is given to Clp then you may get
89   a different continuous optimum and so different cuts and heuristic solutions. This can be switched on by
90   setting randomSeed for Clp and/or randomCbcSeed for Cbc.  The special value of 0 tells code to use time of day
91   for initial seed.
92   
9310. Building on this idea, Andrea Lodi, Matteo Fischetti, Michele Monaci, Domenico Salvagnin, Yuji Shinano, and Andrea Tramontani
94   suggest that this idea be improved by running at the root node with multiple copies of solver, each
95   with its own different seed and then passing in the solutions and cuts so that the main solver has a richer
96   set of solutions and possibly stronger cuts.  This is switched on by setting -multipleRootPasses.  These can also
97   be done in parallel.
98 
9911. Few changes to presolve for special variables and badly scaled problems (in CoinUtils).
100
10112. New option -extraVariables <number> which switches on a trivial re-formulation that introduces extra integer variables
102    to group together variables with same cost.
103
10413. For some problems, cut generators and general branching work better if the problem would be infeasible if the cost is too high.
105    If the new option -constraintFromCutoff is set, the objective function is added as a constraint which rhs is set to the current
106    cutoff value (objective value of best known solution).
107
108Release 2.7.8:
109   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.
110
1111. Change message when LP simplex iteration limit is hit from "Exiting on maximum nodes"
112   to "Exiting on maximum number of iterations"
113
1142. Fix for using overlapping SOS.
115
1163. Fixes in buildsystem.
117
118Release 2.7.7:
119   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.
120
1211. Fix to report interruption on user event if SIGINT is received by CbcSolver.
122   model->status() should now be 5 if this event happened.
123   Added method CbcModel::sayEventHappened() to make cbc stop due to an 'user event'.
124
1252. Other minor fixes.
126
127Release 2.7.6:
128   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.
129
1301. Fixes to build system.
131
1322. Other minor fixes.
133
134Release 2.7.5:
135   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.
136
1371. Fixes to get AMPL interface working again.
138
1392. More fixes to MSVC++ files.
140
141Release 2.7.4:
142   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.
143
1441. Minor bugfixes.
145
146Release 2.7.3:
147   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.
148
1491. Minor bugfixes.
150
1512. Fixes to MSVC++ files.
152
153Release 2.7.2:
154   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.
155
1561. Allow row/column names for GMPL models.
157
1582. Added CbcModel::haveMultiThreadSupport() to indicate whether Cbc library has been compiled with multithread support.
159
1603. Added CbcModel::waitingForMiniBranchAndBound() to indicate whether sub-MIP heuristic is currently running.
161
1624. Cbc shell should work with readline if configured with --enable-gnu-packages.
163
1645. Support for compressed input files (.gz, .bz2) is now enabled by default.
165
1666. Fix problems with relative gap tolerance > 100% and further bugs.
167
1687. Fixes for MSVC++ Version 9 files.
169
1708. Minor fixes in buildsystem; update to BuildTools 0.7.1.
171
172Release 2.7.1:
173   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.
174
1751. Fixes to MSVC++ files
176
177Release 2.7.0:
178
1791. License has been changed to the EPL.
180
1812. Support for MSVC++ version 10 added.
182
1833. Support for BuildTools version 0.7 to incorporate recent enhancements,
184including proper library versioning in Linux, prohibiting installation of
185private headers, etc.
186
1874. Updated externals to new stable versions of dependent projects.
188
1895. Improvements to heuristics.
190
1916. New options for cut generation.
192
1937. Improved reporting of results.
194
1958. Improvements to documentation.
196
1979. Minor bug fixes.
198
199SUPPORT
200=======
201
2021. List Serve
203
204CBC users should use the Cbc mailing list. To subscribe, go to
205http://list.coin-or.org/mailman/listinfo/cbc
206
2073. Bug Reports
208
209Bug reports should be reported on the CBC development web site at
210
211https://projects.coin-or.org/Cbc/newticket
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