[codahale]

The hash array mapped trie was committed to trunk 3 months ago and was first released in 2.8.0.RC1 (which no one uses due to various bugs) and is now available in 2.8.0.RC2 (which very few people are using due to binary incompatibility).

In contrast, Clojure's PersistentHashMap dates back to 2007 and was in both the 1.0 and 1.1.0 releases.

[Artemidoros]

Is it unreasonable to expect that Scala's persistent collections will work comparably to Closure's when 2.8 final is released?

[codahale]

That doesn't sound unreasonable, no -- at some point in the future, Scala's hash array mapped trie will be robust and highly optimized. If your plan is to wait until then, you might be able to speed things up by helping them out yourself.

In the meantime, I benchmarked Yoink's PeristentHashMap against 2.8.0.RC2's immutable.HashMap by a) creating a map of 100,000 sequential keys and then removing them all, and b) creating a map of 100,000 random keys and then removing 100,000 random keys. In the first case, Yoink was 20.7041% (±1.83693%) faster. In the second case, Yoink was 24.7834% (±4.17055%) faster. (Student's t distribution, 95% confidence interval, source is in src/test on the GitHub project and I used ministat for the statistical analysis [a cross-platform port of which is also available on my GitHub page].)

So to summarize, I have a provably faster hash array mapped trie at almost zero cost right now because I spent a few hours with a "good learning experience."

[Artemidoros]

I'm not disputing that Clojure's data structures right now are more performant than Scala's or that your project was worthless. I even apologized in case my original post was badly worded.

What I wanted to confer was that, you _might_ have been wasting a lot of effort because I assumed that you might not have been informed about work of the Scala team that has a high likelihood of obsoleting your project in the near future. Obviously you were informed and my notice was inappropriate. Be assured it won't happen again.

If increasing the performance by about 1/4 for your use cases - compared to the current beta - is valuable for you, great! For me it wouldn't have been worth a few hours. 'A good learning experience' would have. But obviously your values are different.