Semi-continuous challenge

I have carefully chosen these six problems so that it should be quite difficult to solve them all efficiently with a given parametric optimisation method, that is to say by keeping the same parameter set. They are placed in ascending order of theoretical difficulty. For each case, the minimal value is zero, and the objective is to find a function value smaller than 10. I also give the C source code in the appendix. . Name Difficulty Formula Search space Objective