Given a set of matrix $M_i$, by picking a sign coefficient $S_i\in\{-1,1\}$
How can I effectively find a combination that the sum $M^*= \sum_{i=1}^N S_iM_i$ is a nonnegative matrix.
i.e. ${M^*}_{i,j}\geq0$ $\forall i,j$
Given a set of matrix $M_i$, by picking a sign coefficient $S_i\in\{-1,1\}$
How can I effectively find a combination that the sum $M^*= \sum_{i=1}^N S_iM_i$ is a nonnegative matrix.
i.e. ${M^*}_{i,j}\geq0$ $\forall i,j$