<br><font size=2 face="sans-serif">Esben,</font>
<br>
<br><font size=2 face="sans-serif">Error does not seem to exist on branches/devel
but does on trunk (and presumably on stable).</font>
<br>
<br><font size=2 face="sans-serif">Will try and find time to look at it.</font>
<br>
<br><font size=2 face="sans-serif">John Forrest</font>
<br>
<br>
<br>
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<td width=40%><font size=1 face="sans-serif"><b>Esben Mose Hansen <esben@ange.dk></b>
</font>
<br><font size=1 face="sans-serif">Sent by: coin-discuss-bounces@list.coin-or.org</font>
<p><font size=1 face="sans-serif">10/30/2006 10:44 AM</font>
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<div align=center><font size=1 face="sans-serif">Please respond to<br>
Discussions about open source software for Operations Research
<coin-discuss@list.coin-or.org></font></div></table>
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<div align=right><font size=1 face="sans-serif">To</font></div>
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<div align=right><font size=1 face="sans-serif">cc</font></div>
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<div align=right><font size=1 face="sans-serif">Subject</font></div>
<td><font size=1 face="sans-serif">[Coin-discuss] cbc returns non-integer
solution to integer problem</font></table>
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<br><tt><font size=2>Hi list :)<br>
<br>
I hope this is the correct list; it was the closest match I could find
on the <br>
webpage.<br>
<br>
I seem to have hit a bug in cbc. I have a (pure) integer problem, to which
the <br>
cbc solver returns a solution with C000025=0.375. cplex and glpk correctly
<br>
returns a proper solution (with a total cost a bit over 1e6.). Solving
<br>
without using the preprocessor returns the correct answer (but uses 10x
as <br>
much time as glpk). So... is this the correct place for bug reports on
<br>
cbcsolve? Or I am missing something obvious?<br>
<br>
Attached is the original problem in the mps format, and below is a log
of a <br>
session with cbc. <br>
<br>
esben@mosegris:~/ange-fs/externals/solver$ cbc prob.mps -<br>
Coin Cbc and Clp Solver version 1.01.00, build Oct 3 2006<br>
command line - cbc prob.mps -<br>
At line 1 NAME BLANK<br>
At line 2 ROWS<br>
At line 251 COLUMNS<br>
At line 1501 RHS<br>
At line 1589 BOUNDS<br>
At line 1867 ENDATA<br>
Problem BLANK has 247 rows, 277 columns and 2101 elements<br>
Model was imported from ./prob.mps in 0.008001 seconds<br>
Switching to line mode<br>
Coin:solve<br>
Optimal - objective value 6237.92<br>
Cgl0003I 0 fixed, 0 tightened bounds, 88 strengthened rows, 0 substitutions<br>
Cgl0003I 0 fixed, 0 tightened bounds, 88 strengthened rows, 0 substitutions<br>
Cgl0003I 0 fixed, 0 tightened bounds, 80 strengthened rows, 0 substitutions<br>
Cgl0003I 0 fixed, 0 tightened bounds, 80 strengthened rows, 0 substitutions<br>
Cgl0003I 0 fixed, 0 tightened bounds, 80 strengthened rows, 0 substitutions<br>
Cgl0003I 0 fixed, 0 tightened bounds, 80 strengthened rows, 0 substitutions<br>
Cgl0003I 0 fixed, 0 tightened bounds, 80 strengthened rows, 0 substitutions<br>
Cgl0003I 0 fixed, 0 tightened bounds, 80 strengthened rows, 0 substitutions<br>
Cgl0003I 0 fixed, 0 tightened bounds, 80 strengthened rows, 0 substitutions<br>
Cgl0003I 0 fixed, 0 tightened bounds, 80 strengthened rows, 0 substitutions<br>
Cgl0003I 0 fixed, 0 tightened bounds, 80 strengthened rows, 0 substitutions<br>
Cgl0004I processed model has 154 rows, 97 columns (97 integer) and 789
<br>
elements<br>
processed model has 154 rows, 97 columns and 789 elements<br>
Optimal - objective value 6237.51<br>
97 integer variables<br>
Cbc0009I Objective coefficients multiple of 1<br>
cutoff increment increased from 1e-05 to 0.999<br>
<br>
pass 1: obj. 0.00000 --> up = 1 ,
down = 0 - solution found<br>
Cbc0012I Integer solution of 505961 found by heuristic after 1 iterations
and <br>
0 nodes (0.71 seconds)<br>
Cbc0031I 48 added rows had average density of 18.4792<br>
Cbc0013I At root node, 48 cuts changed objective from 6237.51 to 505902
in 100 <br>
passes<br>
Cbc0014I Cut generator 0 (Probing) - 2981 row cuts (26 active), 2 column
cuts <br>
in 1.86412 seconds - new frequency is 1<br>
Cbc0014I Cut generator 1 (Gomory) - 2340 row cuts (16 active), 0 column
cuts <br>
in 0.244013 seconds - new frequency is 1<br>
Cbc0014I Cut generator 2 (Knapsack) - 0 row cuts (0 active), 0 column cuts
in <br>
0.004 seconds - new frequency is -100<br>
Cbc0014I Cut generator 3 (Reduce-and-split) - 178 row cuts (0 active),
0 <br>
column cuts in 0.320027 seconds - new frequency is -100<br>
Cbc0014I Cut generator 4 (Clique) - 0 row cuts (0 active), 0 column cuts
<br>
in -1.75099e-17 seconds - new frequency is -100<br>
Cbc0014I Cut generator 5 (MixedIntegerRounding2) - 64 row cuts (0 active),
0 <br>
column cuts in 0.056004 seconds - new frequency is -100<br>
Cbc0014I Cut generator 6 (FlowCover) - 131 row cuts (0 active), 0 column
cuts <br>
in 0.14401 seconds - new frequency is -100<br>
Cbc0014I Cut generator 7 (TwoMirCuts) - 600 row cuts (6 active), 0 column
cuts <br>
in 0.080004 seconds - new frequency is -100<br>
Cbc0001I Search completed - best objective 505961, took 2887 iterations
and 0 <br>
nodes (4.46 seconds)<br>
Cbc0032I Strong branching done 82 times (3313 iterations), fathomed 1 nodes
<br>
and fixed 18 variables<br>
Cuts at root node changed objective from 6237.51 to 505924<br>
Probing was tried 100 times and created 2981 cuts of which 26 were active
<br>
after adding rounds of cuts ( 1.86412 seconds)<br>
Gomory was tried 100 times and created 2340 cuts of which 16 were active
after <br>
adding rounds of cuts ( 0.244013 seconds)<br>
Knapsack was tried 100 times and created 0 cuts of which 0 were active
after <br>
adding rounds of cuts ( 0.004 seconds)<br>
Reduce-and-split was tried 100 times and created 178 cuts of which 0 were
<br>
active after adding rounds of cuts ( 0.320027 seconds)<br>
Clique was tried 1 times and created 0 cuts of which 0 were active after
<br>
adding rounds of cuts ( -1.75099e-17 seconds)<br>
MixedIntegerRounding2 was tried 100 times and created 64 cuts of which
0 were <br>
active after adding rounds of cuts ( 0.056004 seconds)<br>
FlowCover was tried 100 times and created 131 cuts of which 0 were active
<br>
after adding rounds of cuts ( 0.14401 seconds)<br>
TwoMirCuts was tried 100 times and created 600 cuts of which 6 were active
<br>
after adding rounds of cuts ( 0.080004 seconds)<br>
Result - Finished objective 505961 after 0 nodes and 2887 iterations -
took <br>
4.7683 seconds<br>
Coin:solu $<br>
24 C0000025 1
-3.652224e-17<br>
25 C0000026 0.375
1.1293305e-16<br>
44 C0000045 5
-2.9817938e-14<br>
49 C0000050 7
1.8264526e-14<br>
50 C0000051 1
5<br>
54 C0000055 7
-2.1385815e-14<br>
55 C0000056 1
-2.0385638e-14<br>
59 C0000060 7
2.9942487e-15<br>
60 C0000061 1
4.9042648e-15<br>
62 C0000063 1
2.9317056e-15<br>
64 C0000065 6
-6.539658e-15<br>
65 C0000066 1
-6.362996e-15<br>
69 C0000070 7
1.1726823e-14<br>
70 C0000071 1
7.4609657e-15<br>
74 C0000075 7
2.0091956e-14<br>
75 C0000076 1
2.2095334e-14<br>
77 C0000078 2
2.0459396e-14<br>
79 C0000080 5
2.0459396e-14<br>
80 C0000081 1
2.0725486e-14<br>
84 C0000085 8
2.0826837e-14<br>
89 C0000090 5
-1.1774703e-14<br>
90 C0000091 2
-2.2198539e-14<br>
94 C0000095 4
-1.1476242e-14<br>
95 C0000096 2
-1.1463318e-14<br>
96 C0000097 2
5.3029306e-15<br>
98 C0000099 2
3.9601639e-15<br>
103 C0000104 3
4.9821728e-15<br>
156 C0000157 5
5.3029306e-15<br>
161 C0000162 3
3.0394972e-15<br>
276 C0000277 5
99820<br>
<br>
-- <br>
kind regards, Esben<br>
[attachment "prob.mps.bz2" deleted by John J Forrest/Watson/IBM]
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