source: releases/2.9.1/Cbc/README

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merge r1938 from stable/2.8

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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 A (somehwat outdated) user's manual is available here: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 2.8.3:
29
301. Fix for handling SOS.
31
32Release 2.8.2:
33
341. Fixed recognition of Glpk source in main configure.
35
362. Minor bugfixes in CoinUtils, Clp, and Cbc.
37
38Release 2.8.1:
39
40   Ted, please fill this in!
41
42Release 2.8.0:
43
441. Introduced new secondaryStatus 8 to indicate that solving stopped due to an iteration limit.
45
462. Solution pool is now accessible via the command line and the CbcMain* interface.
47
483. New mipstart option to read an initial feasible solution from a file. Only values for discrete
49   variables need to be provided.
50
514. Added Proximity Search heuristic by Fischetti and Monaci (off by default):
52   The simplest way to switch it on using stand-alone version is "-proximity on".
53
54   Proximity Search is the new "No-Neighborhood Search" 0-1 MIP refinement heuristic recently proposed by
55   Fischetti and Monaci (2012). The idea is to define a sub-MIP without additional constraints but with a
56   modified objective function intended to attract the search in the proximity of the incumbent. The approach
57   works well for 0-1 MIPs whose solution landscape is not too irregular (meaning the there is reasonable
58   probability of finding an improved solution by flipping a small number of binary variables), in particular
59   when it is applied to the first heuristic solutions found at the root node.
60   
615. An implementation of Zero-Half-Cuts by Alberto Caprara is now available.
62   By default, these cuts are off.  To use add to your command line -zerohalfCuts root (or other options) or just -zero.
63   So far, they may help only on a small subset of problems and may need some tuning.
64
65   The implementation of these cuts is described in
66   G. Andreello, A. Caprara, and M. Fischetti
67   "Embedding Cuts in a Branch and Cut Framework: a Computational Study with {0,1/2}-Cuts"
68   INFORMS Journal on Computing 19(2), 229-238, 2007
69   http://dx.doi.org/10.1287/ijoc.1050.0162
70
716. An alternative implementation of a reduce and split cut generator by Giacomo Nannicini is now available.
72   By default, these cuts are off.  To use add to your command line -reduce2AndSplitCuts root (or other options).
73
74   The implementation of these cuts is described in
75   G. Cornuejols and G. Nannicini
76   "Practical strategies for generating rank-1 split cuts in mixed-integer linear programming"
77   Mathematical Programming Computation 3(4), 281-318, 2011
78   http://dx.doi.org/10.1007/s12532-011-0028-6
79
807. An alternative robust implementation of a Gomory cut generator by Giacomo Nannicini is now available.
81   By default, these cuts are off.  To use add to your command line -GMI root (or other options).
82
83   The implementation of these cuts is described in
84   G. Cornuejols, F. Margot, and G. Nannicini
85   "On the safety of Gomory cut generators"
86   http://faculty.sutd.edu.sg/~nannicini/index.php?page=publications
87
888. To encourage the use of some of the more exotic/expensive cut generators a parameter -slowcutpasses has been added.
89   The idea is that the code does these cuts just a few times - less than the more usual cuts.  The default is 10.
90   The cut generators identified by "may be slow" at present are just Lift and project and ReduceAndSplit (both versions).
91   
929. Allow initialization of random seed by user.  Pseudo-random numbers are used in Cbc and Clp.  In Clp they
93   are used to break ties in degenerate problems, while in Cbc heuristics such as the Feasibility Pump use them   
94   to decide whether to round up or down.  So if a different pseudo-random seed is given to Clp then you may get
95   a different continuous optimum and so different cuts and heuristic solutions. This can be switched on by
96   setting randomSeed for Clp and/or randomCbcSeed for Cbc.  The special value of 0 tells code to use time of day
97   for initial seed.
98   
9910. Building on this idea, Andrea Lodi, Matteo Fischetti, Michele Monaci, Domenico Salvagnin, Yuji Shinano, and Andrea Tramontani
100   suggest that this idea be improved by running at the root node with multiple copies of solver, each
101   with its own different seed and then passing in the solutions and cuts so that the main solver has a richer
102   set of solutions and possibly stronger cuts.  This is switched on by setting -multipleRootPasses.  These can also
103   be done in parallel.
104 
10511. Few changes to presolve for special variables and badly scaled problems (in CoinUtils).
106
10712. New option -extraVariables <number> which switches on a trivial re-formulation that introduces extra integer variables
108    to group together variables with same cost.
109
11013. For some problems, cut generators and general branching work better if the problem would be infeasible if the cost is too high.
111    If the new option -constraintFromCutoff is set, the objective function is added as a constraint which rhs is set to the current
112    cutoff value (objective value of best known solution).
113
114Release 2.7.8:
115   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.
116
1171. Change message when LP simplex iteration limit is hit from "Exiting on maximum nodes"
118   to "Exiting on maximum number of iterations"
119
1202. Fix for using overlapping SOS.
121
1223. Fixes in buildsystem.
123
124Release 2.7.7:
125   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.
126
1271. Fix to report interruption on user event if SIGINT is received by CbcSolver.
128   model->status() should now be 5 if this event happened.
129   Added method CbcModel::sayEventHappened() to make cbc stop due to an 'user event'.
130
1312. Other minor fixes.
132
133Release 2.7.6:
134   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.
135
1361. Fixes to build system.
137
1382. Other minor fixes.
139
140Release 2.7.5:
141   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.
142
1431. Fixes to get AMPL interface working again.
144
1452. More fixes to MSVC++ files.
146
147Release 2.7.4:
148   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.
149
1501. Minor bugfixes.
151
152Release 2.7.3:
153   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.
154
1551. Minor bugfixes.
156
1572. Fixes to MSVC++ files.
158
159Release 2.7.2:
160   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.
161
1621. Allow row/column names for GMPL models.
163
1642. Added CbcModel::haveMultiThreadSupport() to indicate whether Cbc library has been compiled with multithread support.
165
1663. Added CbcModel::waitingForMiniBranchAndBound() to indicate whether sub-MIP heuristic is currently running.
167
1684. Cbc shell should work with readline if configured with --enable-gnu-packages.
169
1705. Support for compressed input files (.gz, .bz2) is now enabled by default.
171
1726. Fix problems with relative gap tolerance > 100% and further bugs.
173
1747. Fixes for MSVC++ Version 9 files.
175
1768. Minor fixes in buildsystem; update to BuildTools 0.7.1.
177
178Release 2.7.1:
179   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.
180
1811. Fixes to MSVC++ files
182
183Release 2.7.0:
184
1851. License has been changed to the EPL.
186
1872. Support for MSVC++ version 10 added.
188
1893. Support for BuildTools version 0.7 to incorporate recent enhancements,
190including proper library versioning in Linux, prohibiting installation of
191private headers, etc.
192
1934. Updated externals to new stable versions of dependent projects.
194
1955. Improvements to heuristics.
196
1976. New options for cut generation.
198
1997. Improved reporting of results.
200
2018. Improvements to documentation.
202
2039. Minor bug fixes.
204
205SUPPORT
206=======
207
2081. List Serve
209
210CBC users should use the Cbc mailing list. To subscribe, go to
211http://list.coin-or.org/mailman/listinfo/cbc
212
2133. Bug Reports
214
215Bug reports should be reported on the CBC development web site at
216
217https://projects.coin-or.org/Cbc/newticket
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