By K. A. Redish
Communications of the ACM,
January 1971,
Vol. 14 No. 1, Pages 50-51
10.1145/362452.362512
Comments
In his Certification of Algorithm 245 [1], Ralph L. London exhibits a common confusion between an algorithm, its representation, and its implementation on a processor—a code. In the present state of the art we can attempt, in general, to prove an algorithm and to test a code. For example, London states that “… the algorithm TREESORT 3 [2] is proved to perform properly its claimed task of sorting an array M[1:n] into ascending order.” While this is true of the algorithm, it is not true of the code unless we place restrictions on the array elements. The trouble arises in this example from the finite precision of processors; the Boolean expression A ≥ B (real A, B) will usually be implemented as A - B ≥ 0, which can fail due to floating point overflow or underflow.
The full text of this article is premium content
No entries found
Log in to Read the Full Article
Need Access?
Please select one of the options below for access to premium content and features.
Create a Web Account
If you are already an ACM member, Communications subscriber, or Digital Library subscriber, please set up a web account to access premium content on this site.
Join the ACM
Become a member to take full advantage of ACM's outstanding computing information resources, networking opportunities, and other benefits.
Subscribe to Communications of the ACM Magazine
Get full access to 50+ years of CACM content and receive the print version of the magazine monthly.
Purchase the Article
Non-members can purchase this article or a copy of the magazine in which it appears.
