Re: [Caml-list] Optimizing pure-functional streams

[Simon Cruanes <simon.cruanes.2007@m4x.org>]

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Hello,

Iterators in OCaml have been the topic of many discussions. Another
option for fast iterators is https://github.com/c-cube/sequence ,
which (with flambda) should compile down to loops and tests on this kind
of benchmark. With the attached additional file on 4.04.0+flambda,
I obtain the following (where sequence is test-seq):

$ for i in test-* ; do echo $i ; time ./$i ; done
test-c_loop
5000000100000000
./$i  0.08s user 0.00s system 97% cpu 0.085 total
test-f_loop
5000000100000000
./$i  0.10s user 0.00s system 96% cpu 0.100 total
test-loop
5000000100000000
./$i  0.18s user 0.00s system 97% cpu 0.184 total
test-seq
5000000100000000
./$i  0.11s user 0.00s system 97% cpu 0.113 total
test-stream
5000000100000000
./$i  0.44s user 0.00s system 98% cpu 0.449 total


Note that sequence is imperative underneath, but can be safely used as a
functional structure.

-- 
Simon Cruanes

http://weusepgp.info/
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type 'a seq = ('a -> unit) -> unit

let enum high k =
  for i = 1 to high do k i done
[@@inline always]

let sum s =
  let n = ref 0 in
  s (fun x -> n := !n + x);
  !n
[@@inline always]

let filter pred seq k =
  seq (fun x -> if pred x then k x)
[@@inline always]

let map f seq k =
  seq (fun x -> k (f x))
[@@inline always]

let high = 1000 * 1000 * 100

let res = enum high
	|> filter (fun x -> x mod 2 = 0)
	|> map (( * ) 2)
	|> sum

let _ = Printf.printf "%d\n" res

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