Does OR Tools SCIP solver not employ constraints?

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No, OR Tools SCIP solver employs constraints. SCIP (Solving Constraint Integer Programs) is a constraint integer programming solver that can handle linear and nonlinear problems with continuous and/or integer variables. It uses constraint propagation to reduce the search space and can prove optimality or infeasibility of a problem. SCIP also supports a wide range of constraints including linear, quadratic, and nonlinear constraints.