[Bonmin] Assertion in OsiSimpleInteger::createBranch()

[Stefan Vigerske]

Hi,

it sounds as if Bonmin tries to branch on a fixed integer variable.
You might want to trace who created this OsiBranchingInformation and why 
this has happened.

Also consider upgrading to Bonmin 1.8.5 or 1.8.6 first. Bonmin 1.8.4 is 
21 months old.

Stefan

On 06/20/2017 03:16 PM, David Wilkinson wrote:
> This is a Bonmin question, but I haven't seen any activity in the Bonmin 
> group for a while, so I am sending to the Ipopt group also.
> 
> I am using Bonmin 1.8.4 with "B-BB" algorithm to solve a problem with 
> two integer variables, both with lower bound 0 and upper bound 3, with 
> an initial guess of (1,1). I am seeing an assertion error in 
> OsiSimpleInteger::createBranch() around line 626 of 
> OsiBranchingObject.cpp. The purpose of the assertion is to check that 
> the upper bound for the variable under consideration is greater than the 
> lower bound. When I hit the assertion, the value of columnNumber_ is 0, 
> and both info->lower_[0] and info->upper_[0] are 0.0, so the assertion 
> is correctly triggered.
> 
> Since assertions are not supposed to happen, I initially suspected user 
> (me) error in setting up the problem, but I do not think so, because our 
> driver program repeatedly requests optimizations of a similar type (with 
> different objective and constraint functions, but the same bounds), and 
> several such optimizations have been done correctly before this one. It 
> may be that these optimizations do not fully satisfy the Bonmin 
> convexity requirements, but surely this should not cause an assertion in 
> the code? Our program will tolerate cases where Bonmin fails and emits 
> an exception, and indeed if I throw an exception in 
> OsiSimpleInteger::createBranch() instead of the assertion, our program 
> continues with other successful Bonmin optimizations.
> 
> Any ideas?
> 
> Thanks,
> 
> David Wilkinson
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