Noun
subproblem (plural subproblems)
A problem whose solution contributes to the solution of a larger problem.
A simpler variant of divide and conquer is called a decrease and conquer algorithm, that solves an identical subproblem and uses the solution of this subproblem to solve the bigger problem. Source: Internet
Von Neumann's method used a pivoting algorithm between simplices, with the pivoting decision determined by a nonnegative least squares subproblem with a convexity constraint ( projecting the zero-vector onto the convex hull of the active simplex ). Source: Internet