Author ygale
Date 2004-05-17.13:09:27
SpamBayes Score
Marked as misclassified
Logged In: YES 

Tim, your test fixture is very nice.

I verified your result that there are no collisions
over the fixture set for the algorithm you specified.
Based on that result, I would recommend that we
NOT use your algorithm.

The probability of no collisions is near zero for
250000 random samples taken from a set of 2^32
elements. So the result shows that your algorithm
is far from a good hash function, though it is
constructed to be great for that specific fixture set.

I ran my algorithm on your fixture set using the
table of 64 constants taken from MD5. I got 13
collisions, a reasonable result.

It is not true that I repeat multipliers (very often) -
note that I increment the elements of the table each
time around, so the sequence repeats itself only
after 2^38 tuple elements. Also, my algorithm runs
at esentially the same speed as the current one:
no additional multiplies, only a few adds and increments
and such.
Date User Action Args
2007-08-23 14:21:13adminlinkissue942952 messages
2007-08-23 14:21:13admincreate