One of the core ideas in YALMIP is to rely on external solvers for the low-level numerical solution of optimization problem. YALMIP concentrates on efficient modeling and high-level algorithms.
Linear programming can be solved by quadratic programming which can be solved by second-order cone programming which can be solved by semidefinite programming. Hence, in theory, you only need a semidefinite programming solver if you only solve linear problems. In practice though, dedicated solvers are recommended.
If you solve non-trivial linear and quadratic programs (and nonconvex problems via BMIBNB, a dedicated LP/QP solver is recommended. Most examples in this Wiki have been generated using MOSEK, GUROBI and CPLEX. All these solvers have academic licenses giving access to full unlimited versions.
If you intend to solve large problems or other problem classes, you are advised to download several solvers to find one that works best for your problem.
And finally, there are no free lunches and you get what you pay for (unless you’re in academia!).
Available solvers by problem class
A simple categorization is as follows (the definitions of free and commercial depends slightly on the solver, please see the specific comments in the solver description)
Linear programming (free)
Mixed Integer Linear programming (free)
Linear programming (commercial)
Mixed Integer Linear programming (commercial)
Quadratic programming (free)
Quadratic programming (commercial)
Mixed Integer Quadratic programming (commercial)
Second-order cone programming (free)
Second-order cone programming (commercial)
Mixed Integer Second-order cone programming (commercial)
Semidefinite programming (free)
Semidefinite programming (commercial)
General nonlinear programming and other solvers
By exploiting the optimization infrastructure in YALMIP, it is fairly easy to develop algorithms based on the external solvers. This has motivated development of mixed integer conic solvers (BNB, CUTSDP), indefinite quadratic programming (BMIBNB, KKTQP ), simple quasi-convex problems (bisection), sum-of-squares and semidefinite relaxation modules (solvesos, solvemoment) and a global solver for pretty much any nonlinear problem (BMIBNB), just to mention some of the most important modules in YALMIP.