min ρ1 (V), ||ρ1||0 k max

The vertices not in support of target distributionρ1 may then be viewed as being matched to (a subset of)14 adjacent vertices that they transfer flow to. Then, we require the vertices in support of optimalρ1 to have a strictly higher signal that the vertices19 not inthe support. In contrast, there are no major computational35 bottlenecks in our approach. In particular, please note that both the projection steps in Algorithm 2 can be solved36 efficiently byexisting algorithms.