java.util.HashMap issues -- SimpleORM Benchmarking

I have been tidying up the benchmarks, and I have installed and 
tested against Oracle 11g.

The Netbeans profiling suggests that our main performance issue is 
the HashMap in SDataSet.  We are getting *Many* collisions, with our 
Equals method sometimes being called dozens of times per hash lookup 
(SDataSet.contains).

I checked the hash code, and the values returned look fine -- no 
duplicates.  I tried making the hash map huge, still lots of collisions.

Then I looked at the strange hash code in Java, which is well described in
   http://hioctane.blogspot.com/2005/09/some-insight-into-hashmap-and-hashcode.html

And sure enough, after passing our hash code through their secondary 
hasher we get lots of collisions.

So a better hash map would be good.  Does anyone have one or want to build one?

Set  SDataSet.TRACE_HASH to true to see the traces.

For our (relatively) slow querySequential test the hash takes 140 ms 
out of 203 ms.
(This is actually the fastest test, at 203 micro seconds/record, 
which makes the hash problem visible.)

Anthony



Dr Anthony Berglas, [email protected]       Mobile: +61 4 4838 8874
Just because it is possible to push twigs along the ground with ones nose
does not necessarily mean that is the best way to collect firewood.


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