Re: Hash table performance
On Mon, 23 Nov 2009, Jon Harrop wrote:
Also, some influential people on the JVM Languages mailing list were
discussing what they perceived to be the main issues with the JVM today
and they flagged lack of value types as a major issue. This benchmark
seems to have verified their findings.
Yes, it's something i've been wanting for years. The trouble is that there
are a few little things in java's semantics that make adding value types
(by which i really mean inlined objects, since we're talking about
implementation technique rather than semantics at this point) under the
hood amazingly hard. Adding them as a language-level feature would get
round this, but would be a big change at this point in java's life cycle.
Moreover, I am amazed that I watched a lecture where a guy from Azul
Systems described the enormous lengths they'd gone to in creating a
scalable hash table built upon the JVM for parallel machines. Their
implementation would have to scale across at least 32 cores (far more
than any of today's consumer-level machines) just to catch up with the
CLR!
As long as you only want to store doubles in it. I imagine that if you're
using object keys, the CLR's advantage is rather smaller.
tom
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...
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