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    <p>Not a flood of responses here :) but apparently some interest, so I'll try to answer my own question with what I've learned over the past few days:</p> <ul> <li>With the 1.1 optimization approach (Java primitives and mutable arrays) ~4x slower than optimized Java is about as fast as it goes. </li> <li>The 1.2 constructs <code>definterface</code> and <code>deftype</code> are <strong>more than twice as fast</strong>, coming within ~1.7x (+70%) of Java with shorter, simpler and cleaner code than for 1.1.</li> </ul> <p>Here are the implementations:</p> <ul> <li><a href="http://github.com/j-g-faustus/Clojure-test-code/blob/master/shootout/nbody.clj" rel="noreferrer">Clojure 1.1 approach</a></li> <li><a href="http://github.com/j-g-faustus/Clojure-test-code/blob/master/shootout/nbody_type.clj" rel="noreferrer">Clojure 1.2 approach</a></li> </ul> <p><a href="http://wiki.github.com/j-g-faustus/Clojure-test-code/" rel="noreferrer">More details</a> including "lessons learned", JVM version and profiling screenshots.</p> <p>Subjectively speaking, optimizing the 1.2 code was a breeze compared to optimizing 1.1, so this is very good news for Clojure number crunching. (Actually close to amazing :)</p> <p>The 1.2 testing used the current master branch, I did not try any of the new numeric branches. From what I can gather the new ideas currently being discussed </p> <ul> <li>may make non-optimized numerics faster</li> <li>may speed up the 1.1 version of this benchmark</li> <li>will probably not speed up the 1.2 version, it is already as "close to the metal" as it is likely to get.</li> </ul> <p><strong>Disclaimers:</strong></p> <ul> <li>Clojure 1.2 is not released yet, so 1.2 benchmark results are preliminary.</li> <li>This is one particular benchmark on physics calculations. It is relevant to floating point number crunching, but irrelevant to performance in areas like string parsing, concurrency or web request handling.</li> </ul>
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    1. POClojure number crunching performance
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    1. COYou should try the numeric branches, looking over your code I see places where you will get unnecessarily get boxing under the 1.2 master branch.
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    2. COThanks for the tip. The equiv branch had some impact on the 1.1 version, no noticable difference for the 1.2 version. There may be alternative implementations where the difference is more significant. The equiv branch still looks good, especially primitive type hints and :static.
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    3. COThank your very much for your highly interesting contribution. I especially enjoyed reading the detailed analysis. I compiled the 1.2 version and compared it with the Java example in several runs and it was on average only 1.5x slower. Two questions have been evoked on my part. As you stated in your analysis the code is not idiomatic because it makes use of mutable variables. How much slower would the code perform if immutable variables were used? How much effort would be involved in parallelizing the mutable or the immutable version?
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      1. USStefan Schmidt
 

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