Of course I always show my Sudoku example:
A good MIP solver solves this in zero nodes: the presolver will take care of it completely. E.g. for the 81 x 81 problem below I see:
|Starting Gurobi... |
Optimize a model with 26244 Rows, 531441 Columns and 2125764 NonZeros
Presolve removed 26244 rows and 531441 columns
Presolve time: 1.67s
Model and data files:
Now if these solvers would just be as fast on my real models….