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From Grant Ingersoll <>
Subject Re: [jira] Commented: (MAHOUT-6) Need a matrix implementation
Date Wed, 12 Mar 2008 20:22:41 GMT
Not to mention, we are very young here, and the usual quote about  
optimization applies, so I'd say we not worry too much about  
performance just yet.

Do note, however, that committers can get a free Open Source license  
for YourKit just by asking them.  Same goes for other tools, too, like  
IntelliJ, etc.


On Mar 11, 2008, at 4:15 AM, Dawid Weiss wrote:

>> Try turning on verbose gc.
> Benchmarking is a difficult stuff, really. Much harder than folks  
> usually consider it. Looking at GC, for example, you have to be  
> aware not only of the GC type used (and its settings), but also of  
> the machine the benchmarking is run on.
> In Jason's case, if he's running 64-bit server JVM on a multi-core  
> machine, then the JVM is using a parallel GC and is effectively  
> running behind the scenes :)
> You can also try using YouKit profiler -- it's does really good job  
> at showing heap/ GC usage.
> I am far from being an expert in JVM architecture, but I think boxed  
> primitive types do have very special optimization at low-level and  
> since so produce very little overhead. Also, the collections inside  
> JDK have been optimized heavily since their initial releases. Much  
> like reg-exes: we recently compared a code that used Pattern class  
> and hand-crafted parsing code. The hand-crafted code was 100%  
> faster, but much longer and more difficult to read.
> Dawid

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