[Cbc] bug in Cbc-2.9.0?
John Forrest
john.forrest at fastercoin.com
Sat Mar 28 14:42:33 EDT 2015
Klaus,
This is the same problem with CglGomory that was reported before.
I still don't know why this has started happening - but this is the bad cut
Cut with 6 coefficients, cuts off known solutions by 1.82667e-06,
lo=-1.79769e+308, ub=4.5
Solution was to switch off CglGomory and use CglGMI.
If anyone has a clue what might be happening - please tell me.
John Forrest
On 27/03/15 23:17, Klaus Lux wrote:
> Hi,
> 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:
> I have attched the (input) mps file to this email.
> running cbc on cbc290bug.mps by typing
>
> import cbc290bug.mps
> solve
>
> i get iwith cbc version 2.8.5 an objective vlue of 33 (which seems to
> be correct)
> and with cbc version 2.9.0 an objective value of 34.
> Kind regards,
> Klaus Lux.
> :
> Welcome to the CBC MILP Solver
> Version: 2.8.5
> Build Date: Feb 8 2015
>
> CoinSolver takes input from arguments ( - switches to stdin)
> Enter ? for list of commands or help
> Coin:At line 1 NAME MOC
> At line 2 ROWS
> At line 114 COLUMNS
> At line 355 RHS
> At line 405 BOUNDS
> At line 418 ENDATA
> Problem MOC has 110 rows, 12 columns and 464 elements
> Coin0008I MOC read with 0 errors
> Coin:Continuous objective value is 29 - 0.00 seconds
> Cgl0003I 0 fixed, 1 tightened bounds, 1 strengthened rows, 0
> substitutions
> Cgl0003I 0 fixed, 0 tightened bounds, 1 strengthened rows, 0
> substitutions
> Cgl0004I processed model has 53 rows, 11 columns (11 integer) and 302
> elements
> Cutoff increment increased from 1e-05 to 0.9999
> Cbc0012I Integer solution of 42 found by DiveCoefficient after 0
> iterations and 0 nodes (0.00 seconds)
> Cbc0038I Full problem 53 rows 11 columns, reduced to 13 rows 6 columns
> Cbc0012I Integer solution of 35 found by RINS after 0 iterations and 0
> nodes (0.00 seconds)
> Cbc0038I Full problem 53 rows 11 columns, reduced to 13 rows 6 columns
> Cbc0012I Integer solution of 33 found by DiveCoefficient after 1
> iterations and 0 nodes (0.00 seconds)
> Cbc0038I Full problem 53 rows 11 columns, reduced to 18 rows 7 columns
> Cbc0031I 1 added rows had average density of 3
> Cbc0013I At root node, 1 cuts changed objective from 29 to 33 in 3 passes
> 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
> 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
> 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
> 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
> 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
> 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
> Cbc0001I Search completed - best objective 33.00000000000001, took 1
> iterations and 0 nodes (0.01 seconds)
> Cbc0035I Maximum depth 0, 2 variables fixed on reduced cost
> Cuts at root node changed objective from 29 to 33
> Probing was tried 3 times and created 8 cuts of which 0 were active
> after adding rounds of cuts (0.000 seconds)
> Gomory was tried 3 times and created 3 cuts of which 1 were active
> after adding rounds of cuts (0.000 seconds)
> Knapsack was tried 3 times and created 0 cuts of which 0 were active
> after adding rounds of cuts (0.000 seconds)
> Clique was tried 3 times and created 0 cuts of which 0 were active
> after adding rounds of cuts (0.000 seconds)
> MixedIntegerRounding2 was tried 3 times and created 0 cuts of which 0
> were active after adding rounds of cuts (0.000 seconds)
> FlowCover was tried 1 times and created 0 cuts of which 0 were active
> after adding rounds of cuts (0.000 seconds)
> TwoMirCuts was tried 3 times and created 2 cuts of which 0 were active
> after adding rounds of cuts (0.000 seconds)
>
> Result - Optimal solution found
>
> Objective value: 33.00000000
> Enumerated nodes: 0
> Total iterations: 1
> Time (CPU seconds): 0.01
> Time (Wallclock seconds): 0.01
>
>
>
> but wiith cbc-2.9.0 I get:Welcome to the CBC MILP Solver
> Version: 2.9.0
> Build Date: Jan 31 2015
>
> CoinSolver takes input from arguments ( - switches to stdin)
> Enter ? for list of commands or help
> Coin:At line 1 NAME MOC
> At line 2 ROWS
> At line 114 COLUMNS
> At line 355 RHS
> At line 405 BOUNDS
> At line 418 ENDATA
> Problem MOC has 110 rows, 12 columns and 464 elements
> Coin0008I MOC read with 0 errors
> Coin:Continuous objective value is 29 - 0.00 seconds
> Cgl0003I 0 fixed, 1 tightened bounds, 1 strengthened rows, 0
> substitutions
> Cgl0003I 0 fixed, 0 tightened bounds, 1 strengthened rows, 0
> substitutions
> Cgl0004I processed model has 37 rows, 11 columns (11 integer (1 of
> which binary)) and 250 elements
> Cutoff increment increased from 1e-05 to 0.9999
> Cbc0012I Integer solution of 42 found by DiveCoefficient after 0
> iterations and 0 nodes (0.00 seconds)
> Cbc0038I Full problem 37 rows 11 columns, reduced to 13 rows 6 columns
> Cbc0012I Integer solution of 35 found by RINS after 0 iterations and 0
> nodes (0.00 seconds)
> Cbc0012I Integer solution of 34 found by DiveCoefficient after 4
> iterations and 0 nodes (0.00 seconds)
> Cbc0031I 1 added rows had average density of 3
> Cbc0013I At root node, 1 cuts changed objective from 29 to 34 in 3 passes
> 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
> 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
> 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
> 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
> 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
> 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
> 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
> Cbc0001I Search completed - best objective 34, took 4 iterations and 0
> nodes (0.00 seconds)
> Cbc0035I Maximum depth 0, 2 variables fixed on reduced cost
> Cuts at root node changed objective from 29 to 34
> Probing was tried 3 times and created 7 cuts of which 0 were active
> after adding rounds of cuts (0.000 seconds)
> Gomory was tried 3 times and created 3 cuts of which 0 were active
> after adding rounds of cuts (0.000 seconds)
> Knapsack was tried 3 times and created 0 cuts of which 0 were active
> after adding rounds of cuts (0.000 seconds)
> Clique was tried 3 times and created 0 cuts of which 0 were active
> after adding rounds of cuts (0.000 seconds)
> MixedIntegerRounding2 was tried 3 times and created 0 cuts of which 0
> were active after adding rounds of cuts (0.000 seconds)
> FlowCover was tried 3 times and created 0 cuts of which 0 were active
> after adding rounds of cuts (0.000 seconds)
> TwoMirCuts was tried 3 times and created 2 cuts of which 0 were active
> after adding rounds of cuts (0.000 seconds)
>
> Result - Optimal solution found
>
> Objective value: 34.00000000
> Enumerated nodes: 0
> Total iterations: 4
> Time (CPU seconds): 0.01
> Time (Wallclock seconds): 0.01
>
> Coin:Total time (CPU seconds): 0.01 (Wallclock seconds):
> 0.02
>
>
>
>
>
>
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