Author: Larry Griffiths
Date: 19:20:00 09/16/00
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On September 16, 2000 at 19:25:56, Robert Hyatt wrote: > >This last thing suggests that maybe your hash keys are not as random as they >should be. I have done some hash testing and I don't see any "holes". IE I >can quickly write over nearly *every* position. I detect this by simply running >a search, then counting how many entries are from this search, vs previous >searches. I can get 99% easily... I have a Hash Graph that shows the used and unused entries visually. I do a HashKey%HASHTABLEENTRIES to get a pointer into my hashtable. When I do not have a hashtable that is a power of 2, then my visual graph shows two regions where one of the regions appears to have many more dots in it that the other region of the hash table. Kind of like the following using characters... ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, ................................ ................................ ................................ ................................ where the "," part of the hash table has less unused entries than the "." portion. It only seems to do this when the hash table size is not a power of 2. I will try some more testing to see if the bands hold true for other non powers of 2. Larry.
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