On 8/19/14, 12:01 PM, Ary Borenszweig wrote:
On 8/19/14, 11:51 AM, bearophile wrote:
Ary Borenszweig:
Then here someone from the team says he can't say a way to improve the
performance by an order of magnitude:
https://www.mail-archive.com/[email protected]/msg02856.html
(but I don't know how true is that)
Can't they remove some type inference from the language?
Type inference is handy (but I write down all type signatures in
Haskell, sometimes even for nested functions) but if it costs so much in
compilation time then perhaps isn't it a good idea to remove some type
inference from Rust?
Bye,
bearophile
Crystal has *global* type inference. If you look at the compiler's code
you will find very few type annotations (mostly for generic types and
for arguments types restrictions). Compiling the compiler takes 6
seconds (recompiling it takes 3 seconds).
D also has auto, Nimrod has let, and both compilers are very fast.
I don't think type inference is what makes their compiler slow.
Here are the full stats:
$ time CFG_VERSION=1 CFG_RELEASE=0 rustc -Z time-passes src/librustc/lib.rs
time: 0.519 s parsing
time: 0.026 s gated feature checking
time: 0.000 s crate injection
time: 0.170 s configuration 1
time: 0.083 s plugin loading
time: 0.000 s plugin registration
time: 1.803 s expansion
time: 0.326 s configuration 2
time: 0.309 s maybe building test harness
time: 0.321 s prelude injection
time: 0.363 s assigning node ids and indexing ast
time: 0.023 s checking that all macro invocations are gone
time: 0.031 s external crate/lib resolution
time: 0.046 s language item collection
time: 1.250 s resolution
time: 0.027 s lifetime resolution
time: 0.000 s looking for entry point
time: 0.023 s looking for plugin registrar
time: 0.063 s freevar finding
time: 0.126 s region resolution
time: 0.025 s loop checking
time: 0.047 s stability index
time: 0.126 s type collecting
time: 0.050 s variance inference
time: 0.265 s coherence checking
time: 17.294 s type checking
time: 0.044 s check static items
time: 0.190 s const marking
time: 0.037 s const checking
time: 0.378 s privacy checking
time: 0.080 s intrinsic checking
time: 0.070 s effect checking
time: 0.843 s match checking
time: 0.184 s liveness checking
time: 1.569 s borrow checking
time: 0.518 s kind checking
time: 0.033 s reachability checking
time: 0.204 s death checking
time: 0.835 s lint checking
time: 0.000 s resolving dependency formats
time: 25.645 s translation
time: 1.325 s llvm function passes
time: 0.766 s llvm module passes
time: 40.950 s codegen passes
time: 46.521 s LLVM passes
time: 0.607 s running linker
time: 3.372 s linking
real 1m46.062s
user 1m41.727s
sys 0m3.333s
So apparently type checking takes a long time, and also generating the
llvm code. But it seems waaaay too much for what it is.
Also, the list seems way too big. It's ok from a purist point of view,
to make the compiler nice and clean. But that's not a good way to make a
fast compiler.
The sad thing is that Mozilla is behind the project, so people are
really excited about it. Other languages don't have a big corporation
behind them and have faster compilers (and nicer languages, I think ^_^).
