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Presolves in some GAMS solvers can signal execution errors problems (e.g. OSL, CPLEX, CONOPT). Circumstances where we have seen errors arise.
| • | Presolve can, in relatively simple problems, essentially eliminate the problem. This generally occurs because presolves commonly substitute away bounds and equality constraints to simplify the problem and may in effect simplify the problem out of existence. |
| • | Presolve may detect the problem is unbounded or infeasible and terminate. |
| • | CONOPT may investigate the problem and stop citing scaling inadequacies. |
In such cases, the LST file solution is often mysterious and unusual. Each is illustrated below.
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