At Fri, 28 Feb 2014 10:50:11 -0500, Stephen Bloch wrote: > > On Feb 28, 2014, at 10:34 AM, Vincent St-Amour <stamo...@ccs.neu.edu> wrote: > > > This code is probably the problem: > > > > (require/typed racket/unsafe/ops > > [(unsafe-fx+ index+) [Index Index -> Index]] > > [unsafe-fx+ [Fixnum Fixnum -> Fixnum]] > > [unsafe-fx- (Fixnum Fixnum -> Fixnum)] > > [unsafe-fl+ (Flonum Flonum -> Flonum)] > > [unsafe-fl- (Flonum Flonum -> Flonum)] > > [unsafe-fl* (Flonum Flonum -> Flonum)] > > ) > > > > TR already provides types for these functions, so you can use: > > > > (require racket/unsafe/ops) > > > > `require/typed' adds contracts to its imports (for safe typed-untyped > > interop), which add a significant cost (85% of the running time, > > according to the contract profiler). > > Yike! Thanks; I never would have thought of that. > > There’s probably something in the documentation about “require/typed” > as a source of inefficiency, but for whatever reason I didn’t stumble > upon it.
The "typed-untyped interaction" section of the TR guide does mention the overhead of contracts. I'll add mentions elsewhere in the docs (probably in the caveats and optimization sections). > > Removing the `require/typed' (except for `index+') brings the running > > time (of the portion you were profiling) down from 22s to 15s. Replacing > > the `index+'s with generic `+' and `assert's (to enforce `Index' > > results) brings the running time down to 2.5s. > > Generic ‘+’, not ‘unsafe-fx+’? In this case, Typed Racket optimized it automatically based on the type information, as confirmed by optimization coach. > Should I be using racket/unsafe/ops at all? I would recommend first seeing whether TR already optimizes operations for you. If it doesn't, you can try adjusting the types. If that doesn't work, then unsafe operations are a good option. I tend to use them as a last resort. Unsafe fixnum operations, specifically, are not usually a significant improvement over generic arithmetic, because the fixnum case is already on the fast path of generic operations, and fixnums are not boxed (unlike flonums). Vincent ____________________ Racket Users list: http://lists.racket-lang.org/users
