Semis section not working as expected.

[svigerske]

Issue created by migration from Trac.

Original creator: richiarora

Original creation time: 2018-01-10 15:28:11

Assignee: @tkralphs

Version: 2.9.8

Keywords: semis

Hi

I am using version 2.9.9 of cbc in ubuntu 17.10 docker image.
My test.lp file has following content:

Maximize
 obj: x1 + 2 x2 + 3 x3 + x4
Subject To
 c1: - x1 + x2 + x3 + 10 x4 <= 20
 c2: x1 - 3 x2 + x3 <= 30
 c3: x2 - 3.5 x4 = 0
Bounds
 0 <= x1 <= 40
 2 <= x4 <= 3
General
 x4
Semis
 x1 x2 x3

When trying with semis section i get error
"terminate called after throwing an instance of 'CoinError'
Aborted"

on mac i get:
libc++abi.dylib: terminating with uncaught exception of type CoinError
Abort trap: 6

However if I comment out Semis it works fine.
I was hoping that Semis are supported.
Am I doing something wrong?

My command is : cbc -presolve on -import test.lp solve solu out.txt

On further analysis i found out when in cbc prompt i type "import test.lp" it fails and shows same error is

Thanks

[svigerske]

Looks good with current Cbc/master:

Welcome to the CBC MILP Solver 
Version: Trunk (unstable) 
Build Date: Mar 12 2019 
Revision Number: 2526 

command line - ./cbc issue183.lp (default strategy 1)
 CoinLpIO::readLp(): Maximization problem reformulated as minimization
Continuous objective value is -125.208 - 0.00 seconds
Cgl0004I processed model has 3 rows, 4 columns (1 integer (0 of which binary)) and 9 elements
Cbc0036I Heuristics switched off as 3 branching objects are of wrong type
Cbc0031I 1 added rows had average density of 4
Cbc0013I At root node, 1 cuts changed objective from -125.20833 to -122.5 in 2 passes
Cbc0014I Cut generator 0 (Probing) - 0 row cuts average 0.0 elements, 0 column cuts (0 active)  in 0.000 seconds - new frequency is -100
Cbc0014I Cut generator 1 (Gomory) - 1 row cuts average 4.0 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
Cbc0004I Integer solution of -122.5 found after 1 iterations and 0 nodes (0.00 seconds)
Cbc0001I Search completed - best objective -122.5, took 1 iterations and 0 nodes (0.00 seconds)
Cbc0035I Maximum depth 0, 0 variables fixed on reduced cost
Cuts at root node changed objective from -125.208 to -122.5
Probing was tried 2 times and created 0 cuts of which 0 were active after adding rounds of cuts (0.000 seconds)
Gomory was tried 2 times and created 1 cuts of which 0 were active after adding rounds of cuts (0.000 seconds)
Knapsack was tried 2 times and created 0 cuts of which 0 were active after adding rounds of cuts (0.000 seconds)
Clique was tried 2 times and created 0 cuts of which 0 were active after adding rounds of cuts (0.000 seconds)
MixedIntegerRounding2 was tried 2 times and created 0 cuts of which 0 were active after adding rounds of cuts (0.000 seconds)
FlowCover was tried 2 times and created 0 cuts of which 0 were active after adding rounds of cuts (0.000 seconds)
TwoMirCuts was tried 1 times and created 0 cuts of which 0 were active after adding rounds of cuts (0.000 seconds)
ZeroHalf was tried 1 times and created 0 cuts of which 0 were active after adding rounds of cuts (0.000 seconds)
3 bounds tightened after postprocessing


Result - Optimal solution found

Objective value:                -122.50000000
Enumerated nodes:               0
Total iterations:               1
Time (CPU seconds):             0.00
Time (Wallclock seconds):       0.02

Total time (CPU seconds):       0.00   (Wallclock seconds):       0.02

See also https://list.coin-or.org/pipermail/cbc/2018-January/002347.html