我试过使用 scalac -optimise版本 2.7.7。当时我从未得到任何性能改进，但编译时间更长。
Scala 2.9.0 的情况是否更好？该标志目前涵盖哪些优化？
请您参考如下方法:
奇怪，居然还有similar question on the scala-user group :
Rex Kerr当时的回答(五月):
I have never found a case where production code was significantly sped up by using
-optimise, at least when using the Sun JVM. I grant that in some cases it could happen, but it seems to apply similar optimizations to what the JVM does already. Perhaps if there are limits on optimization depth, using -optimise would remove a few layers and then allow the JVM to get a few more. But I mostly don't even bother testing it any more, given how many cases (dozens) I've tried it where the runtime hasn't changed measurably.I expect it would have an impact on VMs that are more conservative (e.g. JRockit) or less sophisticated (e.g. Dalvik).
Ismael Juma添加:
The scala distribution is actually compiled with -optimise, but indeed it's not on unless the argument is passed to scalac.
Is it not mature enough, or could it lead to bugs, changed semantic, etc ?
据我了解，团队决定保守并启用
它仅用于 Scala 分布作为初始步骤(在 Scala 中
2.8.0)。也许考虑在下一个扩展它是个好主意
主要发布。
对于'-optimise的影响'(以及其他因素)在 Scala2.9 中，请参阅此 scala-language thread called "Scala2.9 slower?" .
I'm a bit concerned. After seeing that
-optimizereally does optimize "for comprehensions" on 2.9.0, I then benchmarked the code, and discovered it was about 2.5 times slower than 2.8.1.
结果留下了……复杂的感觉。
