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<div class="moz-cite-prefix">Klaus,<br>
<br>
This is the same problem with CglGomory that was reported before.<br>
<br>
I still don't know why this has started happening - but this is
the bad cut<br>
<br>
Cut with 6 coefficients, cuts off known solutions by 1.82667e-06,
lo=-1.79769e+308, ub=4.5<br>
<br>
Solution was to switch off CglGomory and use CglGMI.<br>
<br>
If anyone has a clue what might be happening - please tell me.<br>
<br>
John Forrest<br>
<br>
On 27/03/15 23:17, Klaus Lux wrote:<br>
</div>
<blockquote cite="mid:5515E525.90307@math.arizona.edu" type="cite">Hi,
<br>
i would like to report a Cbc run, which returns different answers
according to whether I use cbc-2.8.5 or cbc.-2.9.0:
<br>
I have attched the (input) mps file to this email.
<br>
running cbc on cbc290bug.mps by typing
<br>
<br>
import cbc290bug.mps
<br>
solve
<br>
<br>
i get iwith cbc version 2.8.5 an objective vlue of 33 (which seems
to be correct)
<br>
and with cbc version 2.9.0 an objective value of 34.
<br>
Kind regards,
<br>
Klaus Lux.
<br>
:
<br>
Welcome to the CBC MILP Solver
<br>
Version: 2.8.5
<br>
Build Date: Feb 8 2015
<br>
<br>
CoinSolver takes input from arguments ( - switches to stdin)
<br>
Enter ? for list of commands or help
<br>
Coin:At line 1 NAME MOC
<br>
At line 2 ROWS
<br>
At line 114 COLUMNS
<br>
At line 355 RHS
<br>
At line 405 BOUNDS
<br>
At line 418 ENDATA
<br>
Problem MOC has 110 rows, 12 columns and 464 elements
<br>
Coin0008I MOC read with 0 errors
<br>
Coin:Continuous objective value is 29 - 0.00 seconds
<br>
Cgl0003I 0 fixed, 1 tightened bounds, 1 strengthened rows, 0
substitutions
<br>
Cgl0003I 0 fixed, 0 tightened bounds, 1 strengthened rows, 0
substitutions
<br>
Cgl0004I processed model has 53 rows, 11 columns (11 integer) and
302 elements
<br>
Cutoff increment increased from 1e-05 to 0.9999
<br>
Cbc0012I Integer solution of 42 found by DiveCoefficient after 0
iterations and 0 nodes (0.00 seconds)
<br>
Cbc0038I Full problem 53 rows 11 columns, reduced to 13 rows 6
columns
<br>
Cbc0012I Integer solution of 35 found by RINS after 0 iterations
and 0 nodes (0.00 seconds)
<br>
Cbc0038I Full problem 53 rows 11 columns, reduced to 13 rows 6
columns
<br>
Cbc0012I Integer solution of 33 found by DiveCoefficient after 1
iterations and 0 nodes (0.00 seconds)
<br>
Cbc0038I Full problem 53 rows 11 columns, reduced to 18 rows 7
columns
<br>
Cbc0031I 1 added rows had average density of 3
<br>
Cbc0013I At root node, 1 cuts changed objective from 29 to 33 in 3
passes
<br>
Cbc0014I Cut generator 0 (Probing) - 0 row cuts average 0.0
elements, 8 column cuts (8 active) in 0.000 seconds - new
frequency is 1
<br>
Cbc0014I Cut generator 1 (Gomory) - 3 row cuts average 4.7
elements, 0 column cuts (1 active) in 0.000 seconds - new
frequency is 1
<br>
Cbc0014I Cut generator 2 (Knapsack) - 0 row cuts average 0.0
elements, 0 column cuts (0 active) in 0.000 seconds - new
frequency is -100
<br>
Cbc0014I Cut generator 3 (Clique) - 0 row cuts average 0.0
elements, 0 column cuts (0 active) in 0.000 seconds - new
frequency is -100
<br>
Cbc0014I Cut generator 4 (MixedIntegerRounding2) - 0 row cuts
average 0.0 elements, 0 column cuts (0 active) in 0.000 seconds -
new frequency is -100
<br>
Cbc0014I Cut generator 6 (TwoMirCuts) - 2 row cuts average 3.5
elements, 0 column cuts (0 active) in 0.000 seconds - new
frequency is 1
<br>
Cbc0001I Search completed - best objective 33.00000000000001, took
1 iterations and 0 nodes (0.01 seconds)
<br>
Cbc0035I Maximum depth 0, 2 variables fixed on reduced cost
<br>
Cuts at root node changed objective from 29 to 33
<br>
Probing was tried 3 times and created 8 cuts of which 0 were
active after adding rounds of cuts (0.000 seconds)
<br>
Gomory was tried 3 times and created 3 cuts of which 1 were active
after adding rounds of cuts (0.000 seconds)
<br>
Knapsack was tried 3 times and created 0 cuts of which 0 were
active after adding rounds of cuts (0.000 seconds)
<br>
Clique was tried 3 times and created 0 cuts of which 0 were active
after adding rounds of cuts (0.000 seconds)
<br>
MixedIntegerRounding2 was tried 3 times and created 0 cuts of
which 0 were active after adding rounds of cuts (0.000 seconds)
<br>
FlowCover was tried 1 times and created 0 cuts of which 0 were
active after adding rounds of cuts (0.000 seconds)
<br>
TwoMirCuts was tried 3 times and created 2 cuts of which 0 were
active after adding rounds of cuts (0.000 seconds)
<br>
<br>
Result - Optimal solution found
<br>
<br>
Objective value: 33.00000000
<br>
Enumerated nodes: 0
<br>
Total iterations: 1
<br>
Time (CPU seconds): 0.01
<br>
Time (Wallclock seconds): 0.01
<br>
<br>
<br>
<br>
but wiith cbc-2.9.0 I get:Welcome to the CBC MILP Solver
<br>
Version: 2.9.0
<br>
Build Date: Jan 31 2015
<br>
<br>
CoinSolver takes input from arguments ( - switches to stdin)
<br>
Enter ? for list of commands or help
<br>
Coin:At line 1 NAME MOC
<br>
At line 2 ROWS
<br>
At line 114 COLUMNS
<br>
At line 355 RHS
<br>
At line 405 BOUNDS
<br>
At line 418 ENDATA
<br>
Problem MOC has 110 rows, 12 columns and 464 elements
<br>
Coin0008I MOC read with 0 errors
<br>
Coin:Continuous objective value is 29 - 0.00 seconds
<br>
Cgl0003I 0 fixed, 1 tightened bounds, 1 strengthened rows, 0
substitutions
<br>
Cgl0003I 0 fixed, 0 tightened bounds, 1 strengthened rows, 0
substitutions
<br>
Cgl0004I processed model has 37 rows, 11 columns (11 integer (1 of
which binary)) and 250 elements
<br>
Cutoff increment increased from 1e-05 to 0.9999
<br>
Cbc0012I Integer solution of 42 found by DiveCoefficient after 0
iterations and 0 nodes (0.00 seconds)
<br>
Cbc0038I Full problem 37 rows 11 columns, reduced to 13 rows 6
columns
<br>
Cbc0012I Integer solution of 35 found by RINS after 0 iterations
and 0 nodes (0.00 seconds)
<br>
Cbc0012I Integer solution of 34 found by DiveCoefficient after 4
iterations and 0 nodes (0.00 seconds)
<br>
Cbc0031I 1 added rows had average density of 3
<br>
Cbc0013I At root node, 1 cuts changed objective from 29 to 34 in 3
passes
<br>
Cbc0014I Cut generator 0 (Probing) - 0 row cuts average 0.0
elements, 7 column cuts (7 active) in 0.000 seconds - new
frequency is 1
<br>
Cbc0014I Cut generator 1 (Gomory) - 3 row cuts average 4.7
elements, 0 column cuts (0 active) in 0.000 seconds - new
frequency is 1
<br>
Cbc0014I Cut generator 2 (Knapsack) - 0 row cuts average 0.0
elements, 0 column cuts (0 active) in 0.000 seconds - new
frequency is -100
<br>
Cbc0014I Cut generator 3 (Clique) - 0 row cuts average 0.0
elements, 0 column cuts (0 active) in 0.000 seconds - new
frequency is -100
<br>
Cbc0014I Cut generator 4 (MixedIntegerRounding2) - 0 row cuts
average 0.0 elements, 0 column cuts (0 active) in 0.000 seconds -
new frequency is -100
<br>
Cbc0014I Cut generator 5 (FlowCover) - 0 row cuts average 0.0
elements, 0 column cuts (0 active) in 0.000 seconds - new
frequency is -100
<br>
Cbc0014I Cut generator 6 (TwoMirCuts) - 2 row cuts average 3.5
elements, 0 column cuts (0 active) in 0.000 seconds - new
frequency is 1
<br>
Cbc0001I Search completed - best objective 34, took 4 iterations
and 0 nodes (0.00 seconds)
<br>
Cbc0035I Maximum depth 0, 2 variables fixed on reduced cost
<br>
Cuts at root node changed objective from 29 to 34
<br>
Probing was tried 3 times and created 7 cuts of which 0 were
active after adding rounds of cuts (0.000 seconds)
<br>
Gomory was tried 3 times and created 3 cuts of which 0 were active
after adding rounds of cuts (0.000 seconds)
<br>
Knapsack was tried 3 times and created 0 cuts of which 0 were
active after adding rounds of cuts (0.000 seconds)
<br>
Clique was tried 3 times and created 0 cuts of which 0 were active
after adding rounds of cuts (0.000 seconds)
<br>
MixedIntegerRounding2 was tried 3 times and created 0 cuts of
which 0 were active after adding rounds of cuts (0.000 seconds)
<br>
FlowCover was tried 3 times and created 0 cuts of which 0 were
active after adding rounds of cuts (0.000 seconds)
<br>
TwoMirCuts was tried 3 times and created 2 cuts of which 0 were
active after adding rounds of cuts (0.000 seconds)
<br>
<br>
Result - Optimal solution found
<br>
<br>
Objective value: 34.00000000
<br>
Enumerated nodes: 0
<br>
Total iterations: 4
<br>
Time (CPU seconds): 0.01
<br>
Time (Wallclock seconds): 0.01
<br>
<br>
Coin:Total time (CPU seconds): 0.01 (Wallclock
seconds): 0.02
<br>
<br>
<br>
<br>
<br>
<br>
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