Those interested in the mathematics of hashing should, predictably, consult Knuth. The 2nd volume, Sorting and searching, of TACP, any edition, contains a section called Hash functions.
On page 509 of the 1st edition there appears the summarizing text: Such considerations suggest that we choose M to be a prime number such that r^k = +|-a modulo M for small k and a. Knuth explains his notation there, and I will not rehearse it here. --jg -- John Gilmore, Ashland, MA 01721 - USA Avant d'imprimer cet e-mail, réfléchissons à l'impact sur l'environnement.
