ochafik
commented
9 years ago Hello,
Thanks for your report !
Loops on general ranges is indeed not supported yet (only inline ranges are), because they're quite a bit more difficult to handle.
Of course in the case of ranges with constant bounds as in your example, the compiler plugin to reach the definition and proceed as usual, but things get nastier when the bounds are general expressions (which is usually the case).
In the general case we'd have to extract the start, end, step and inclusive values of the Range, and the loop code would be more complex, since the way to iterate depends on both the sign of step and the inclusive parameter. Having different loops and a dynamic switch is not an option (code bloat + JIT dispersion), so we'd have weird conditionals in the while loop's condition that would make it slower (albeit probably not that much slower)... Given the complexity, I'm putting this under low priority, even though for sure it would be a nice to have !
Cheers
zOlive
Google Code Info: Author: olivier.chafik Created On: 2011-07-06T15:59:17.000Z
From @ochafik on September 1, 2011 18:34
In Scala, if you run the test
object P005 extends App{ val t = System.currentTimeMillis
val r = (1 to 20) def isDivis(x:Int) = r forall {x % _ == 0} def find(n:Int):Int = if (isDivis(n)) n else find (n+2)
println (find (2)) println((System.currentTimeMillis - t)/1000.0) }
the forall is not optimized to a while loop, and runs in the same time as without ScalaCL.
If you replace the "r" with its value (1 to 20), i.e. def isDivis(x:Int) = (1 to 20) forall {x % _ == 0} it is optimized and runs over 4 times faster.
I think we should be able to get the same performance in both cases, since r is immutable, we know it will still be (1 to 20).
Google Code Info: Issue #: 76 Author: bungle...@googlemail.com Created On: 2011-07-05T22:34:16.000Z Closed On:
Copied from original issue: ochafik/nativelibs4java#78