large datasets under a lower bound on the quality and an upper bound on the cost of the subsample.1 Note that we implicitly assume that reordering of the trials does not influence the relevant properties of the experimental design.2 In some experimental situations, the set of available design points can be modeled as a continuous domain. However, in many applications, the design space is finite. This is the case if each factor has -in principle or effectively -only a finite number of levels that the experimenter can select, or if the optimal design problem corresponds to data sub-selection (see the examples in Section 6). Moreover, the method proposed in this paper can also be useful for solving the problems with continuous design spaces; cf. Section 5.3 The symbols R, R + , N, N 0 , and R k×n denote the sets of real, non-negative real, natural, non-negative integer numbers, and the set of all k × n real matrices, respectively. 4 Therefore, we do not represent designs by normalized (probability) measures, as is frequently done in optimal design, but by non-normalized vectors of numbers of trials.12 Note that the matrix Q + p is symmetric, as is the matrix Q − p defined below, because tr(M 1 H 1 M 2 H 2 ) = tr(M 1 H 2 M 2 H 1 ) for the symmetric non-negative definite matrices M 1 , M 2 , H 1 , and H 2 .