corrected text:
Worth trying first is von Neumann's classical scheme. Divide the value
obtained using the z/Architecture machine instruction CKSUM. Then use its
remainder mod(s), where s is any convenient small prime. The result will often
be an approximately rectangular distribution of the hash values
0, 1, 2, . . . , s - 1.
The use of a composite hashing modulus c is NOT a good idea. Clustering at its
prime factors is all but certain. Using, say, c = 60 = 2^2 x 3 x 5 would yield
clusters at 2, 3, and 5
John Gilmore Ashland, MA 01721-1817 USA
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