[Symphony] Same version of symphony built with different -O options produces different solutions

[Michael Hennebry]

On Thu, 15 Sep 2011, Peter Moceyunas wrote:

> On 9/15/2011 8:58 AM, Ted Ralphs wrote:
>> Hi Pete,
>> 
>> Do the differences you are observing have to do with changes in the optimal 
>> solution value or just what (alternative) optimal solution is actually 
>> produced and/or how long it takes to produce it (what the search tree looks 
>> like)?
> The objective function values are identical, so I am seeing alternate optimal 
> solutions. The alternate solutions are correct.

It seems that for some reason you want to get the same
solution regardless of platform and build parameters.

As others have noted, it can be done, but it can be expensive.

Assumed goal:
Low cost when there is only one optimal solution.
Solve more or less as usual.
Note the bound on any pruned branches.
If the best pruned branch is worse than the optimal solution found,
said optimal solution is unique.
If not, you have a new equality.
add a new objective and resolve.

-- 
Michael   hennebry at web.cs.ndsu.NoDak.edu
"Pessimist: The glass is half empty.
Optimist:   The glass is half full.
Engineer:   The glass is twice as big as it needs to be."