fact: Definition sumprod {k} n := sumprod_down (@sumprod_up k n) None.
imports: Init.Wf Recdef Reals mathcomp(all_ssreflect perm zmodp matrix ssralg) mathcomp(Rstruct) ssrR Reals_ext f2 subgraph_partition tanner fdist channel pproba linearcode ssralg_ext tanner_partition summary ldpc checksum