On "A new common subexpression elimination algorithm for realizing low-complexity higher order digital filters"

  • Authors:
  • Chip-Hong Chang;Mathias Faust

  • Affiliations:
  • Center for High Performance Embedded Systems and the Center for Integrated Circuits and Systems, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore;Center for High Performance Embedded Systems and the Center for Integrated Circuits and Systems, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore

  • Venue:
  • IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems
  • Year:
  • 2010

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Abstract

A thorough analysis of the paper above revealed several controversial arguments about the superiority of binary representation over canonical signed digits (CSD) for common subexpression elimination (CSE). It was improper to model the number of logic operators (LO) required after CSE as a linear sum of independently weighted numbers of nonzero bits, common subexpressions and unpaired bits. The logic depth (LD) penalty of binary CSE had been deemphasized by the errors in the reported LD. This comment corrects the LD of contention resolution algorithm, and points out some contradictions with reference to the latest experimentation of binary, CSD and minimal signed digit number representations for CSE. Upon correcting the error in the reported filter lengths for different stopband attenuations of digital advanced mobile phone system specification, the LO and LD data of the CSE algorithms compared in the above paper are recalculated using the corrected filter coefficient sets.