Re: large parametrized polymorphic variant type combinations take forever to compile

[Sam Steingold <sds@gnu.org>]

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Jacques Garrigue wrote:
> 
> Could you send me your real code, so that I can see whether something
> unexpected is happening?

here is some more information:
file http://sds.podval.org/data/small.zip includes 6 files:

small1.ml small2.ml : define large (~1,000 variants) polymorphic variant
types (non-parametric).
compilation time: ~20 sec each.
small.ml : use small1.ml & small2.ml:
================ small.ml ====================
type t3 = [
| Small1.t1
| Small2.t2
]

let f ~fa ~fb ~fc = function
  | # Small1.t1 as x -> Small1.f ~fa ~fb x
  | # Small2.t2 as x -> Small2.f ~fa ~fb ~fc x
================ small.ml ====================
compilation time:
real    1m28.063s
user    1m8.628s
sys     0m0.828s

smallp1.ml smallp2.ml : define large (~1,000 variants) parametric
polymorphic variant types.
compilation time: ~20 sec each (same as non-parametric)
small_p.ml: use smallp1.ml smallp2.ml:
================ small_p.ml ====================
type ('a,'b,'c) t3 = [
| ('a,'b) Smallp1.t1
| ('a,'b,'c) Smallp2.t2
]

let f ~fa ~fb ~fc = function
  | # Smallp1.t1 as x -> Smallp1.f ~fa ~fb x
  | # Smallp2.t2 as x -> Smallp2.f ~fa ~fb ~fc x
================ small_p.ml ====================
compilation time:
real    29m31.639s
user    25m49.929s
sys     0m10.937s

note that the use of type parameters increased compilation time of "|#"
by a factor of 20!

$ ocamlc -version
3.09.3

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