Minimizing total wire length by flipping modules

Block flipping and white space distribution for wirelength minimization

“…The optimal block flipping problem has been proven to be NP-complete [6]. However, many heuristics [7][8][9][10][11][12][13] were proposed to obtain sub-optimal solutions. A symbolic algorithm [14] based on Boolean decision diagram (BDD) was proposed that can solve the problem optimally to obtain the minimum wirelength for small-sized circuits, e.g.…”

Flipping Modules to MinimizeMaximum Wire Length

“…The problem of minimizing the ETL by flipping modules as well as by rotating modules has been studied earlier by Yamada and Liu [7], Libeskind-Hadas and Liu [6], Ahn [1], and Chong and Sahni [2]. The starting point of all these studies is an already placed module set.…”

NP-hard module rotation problems

“…Chong and Sahni [CHON92] show that ETLF is linearly solvable for the case when the modules are arranged as a matrix in which wires connect only pairs of modules that are in adjacent columns. They also show that ETLF is polynomially solvable for standard cell designs in which wires connect modules in adjacent columns and either the number of module columns is two or the number of modules dependent on any other module is bounded by some constant.…”

“…Chong and Sahni [CHON92] also evaluate a simple greedy heuristic that attempts to minimize ETL by flipping modules. Experimental results reported by them indicate this heuristic is superior to the neural network approach of [LIBE89].…”