Author: Bas Hamstra
Date: 09:50:12 05/29/04
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On May 29, 2004 at 11:10:47, James Swafford wrote: >In a recent post, Tord suggested setting a flag in >the search when the hash table suggests a fail high, and >testing whether the search would indeed fail high. > >The idea seems so simple I'm embarassed I haven't thought >of it before. :) > >I've been 'pretty sure' for a long time that I've got some >nasty hash bugs. I'm in the mood to exterminate them. > >Last night I implemented Tord's idea and, to my dismay >(but not to my surprise) my hash table is saying 'fail >high' when the search wouldn't have failed high. And- >it doesn't take very long. :) > >This seems like a nasty thing to debug. I'm comtemplating >how I might go about it. I'm hoping some of you can >provide some suggestions... > >-- >James What you describe is not a good way of finding HT bugs, IMO. To start with, hash can cause inconsistent search results, even with completely bugfree code. Want to track hash bugs? Do this: write code to completely recalculate hashkey from scratch. Compare this key with the incremental key at every node. Analyze and fix differences until they are all gone. Bas.
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