Recently il Itas lee11 noticed I l l n l for semigroup conapulaItons nrld for s~lcrlintr, t*rrlrirrgrilnr ntesltes with rnttlfiple lroadcnstirig yicid Jnsler algoriibnas Lhan thew square co?~ntct*prrrls. T l r~ rorltribl~iion oj this paper is Lo y~rouide y c i n n o l l~r r eznrr11jlc 01 a fiinda7nentaI prolltrrl [or WILLCIA t h i s pbelior~ietlott occars. We show i l~n t the prabl~ul o j cotripuli~g lhe convex hull of n sel 4 11 ~o r t e d p o~l i t s in E6e plane 1 1 can be solved it1 O(t) log. 11) firire 011 a rectasgtalar OR d sq1111re mesh of stze fi x fi ruri in 0(7a i) time sn case the H P O~I I~S nre IHI-FIS 111 11 hin(lr*$ Y'IHIIJP, find Figure 1: A 4 x 5 mesh with multiple broadcnsting 1 = t n 0 1 7 1 6 I o g 3~t ) Itrtrr fill. c~l . f r r l pnitrlx rrr Ihc plarlc.