Carry Propagation in Multiplication by Constants
Document Type
Article
Department
Mathematics (HMC)
Publication Date
2011
Abstract
Suppose that a random n-bit number V is multiplied by an odd constant M ≥ 3, by adding shifted versions of the number V corresponding to the 1s in the binary representation of the constant M. Suppose further that the additions are performed by carry-save adders until the number of summands is reduced to two, at which time the final addition is performed by a carry-propagate adder. We show that in this situation the distribution of the length of the longest carry-propagation chain in the final addition is the same (up to terms tending to 0 as n → ∞) as when two independent n-bit numbers are added, and in particular the mean and variance are the same (again up to terms tending to 0). This result applies to all possible orders of performing the carry-save additions.
Rights Information
© 2011 Association for Computing Machinery
Terms of Use & License Information
DOI
10.1145/2000807.2000822
Recommended Citation
Izsak, A. and Pippenger, N. "Carry Propagation in Multiplication by Constants,," ACM Trans. Algorithms, 7:4 (2011) Art. 54, 11. doi: 10.1145/2000807.2000822
