Consider the computations at a node in the message passing algorithms. Assume that the node has incoming and outgoing messages x = (x1, x2, . . . , xn) and y = (y1, y2, . . . , yn), respectively. In this paper, we investigate a class of structures that can be adopted by the node for computing y from x, where each yj, j = 1, 2, . . . , n is computed via a binary tree with leaves x excluding xj. We have three main contributions regarding this class of structures. First, we prove that the minimum complexity of such a structure is 3n − 6, and if a structure has such complexity, its minimum latency is δ + log(n − 2 δ ) with δ = log(n/2) . Second, we prove that the minimum latency of such a structure is log(n − 1) , and if a structure has such latency, its minimum complexity is n log(n − 1) when n − 1 is a power of two. Third, given (n, τ ) with τ ≥ log(n − 1) , we propose a construction for a structure which likely has the minimum complexity among structures with latencies at most τ . Our construction method runs in O(n 3 log 2 (n)) time, and the obtained structure has complexity at most (generally much smaller than) n log(n) − 2.