Sbt and the Fast Scala Compiler?

Question

Does sbt make use of fsc? For test purposes I am compiling a 500-line program on a fairly slow Ubuntu machine (Atom N270). Three successive compile times were 77s, 66s, and 66s.

I then compiled the file with fsc from the command line. Now my times were 80s, 25s, 18s. Better! That implies to me sbt is not using fsc. Am I right? If so, why doesn't it use it?

I may try getting sbt to explicitly use fsc to compile, though I am not sure I will figure out the config. Has anyone done this?

Thanks!

Answer 1

SBT cannot benefit from the Fast Scala Compiler when you run it interactively (with our without using its continuous build mode) because the Scala compiler classes are loaded and get "warmed up" and JIT-ed, which is the entirety of fsc's advantage.