LBFGSHessian: return a positive number of Hessian nonzeros. Should be replaced with has_curvature()

Author: cvanaret

uno/ingredients/hessian_models/quasi_newton/LBFGSHessian.cpp

@@ -39,8 +39,9 @@ namespace uno {
       this->Hessian_approximation = DenseMatrix<double>(this->dimension, this->dimension);
    }
 
-   size_t LBFGSHessian::number_nonzeros(const Model& /*model*/) const {
-      throw std::runtime_error("LBFGSHessian::number_nonzeros should not be called");
+   size_t LBFGSHessian::number_nonzeros(const Model& model) const {
+      // return dummy number for now
+      return model.number_variables * model.number_variables;
    }
 
    void LBFGSHessian::initialize_statistics(Statistics& statistics, const Options& options) const {

uno/model/Model.cpp

@@ -28,4 +28,4 @@ namespace uno {
       const double upper_bound_violation = std::max(0., constraint_value - this->constraint_upper_bound(constraint_index));
       return std::max(lower_bound_violation, upper_bound_violation);
    }
-} // namespace
+} // namespace