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Here is a narrowed-down example, the first case works, but the second one refuses to use the compiled version:

 Compile[{}, Permutations[{1, 2, 3}]][]

 Compile[{}, Permutations[{1, 2, 3}, {2}]][]

Full code:

Compile[{},
  Module[{c, d, e, g, l, m, o, t, w, A = 10^Range[5, 0, -1]}, 
   Do[{c, d, e, g, l, m, o, t, w} = x;
    If[{w, w, w, d, o, t}.A - {g, o, o, g, l, e}.A == {d, o, t, c, o, 
        m}.A, Print@x], {x, Permutations[Range[0, 9], {9}]}]]
  ][]
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1 Answer 1

up vote 4 down vote accepted

In fact, Compile really doesn't work with either of them, a fact revealed by the appearance of the MainEvaluate in the output of CompilePrint.

Needs["CompiledFunctionTools`"]
f1 = Compile[{}, Permutations[{1, 2, 3}]];
f2 = Compile[{}, Permutations[{1, 2, 3}, {2}]];
CompilePrint[f1]

(*
    No argument
    2 Tensor registers
    Underflow checking off
    Overflow checking off
    Integer overflow checking on
    RuntimeAttributes -> {}

    T(I1)0 = {1, 2, 3}
    Result = T(I2)1

1   T(I2)1 = MainEvaluate[ Hold[Permutations][ T(I1)0]]
2   Return
*)

We'd like it to look more like the following, in which MainEvaluate does not appear:

f3 = Compile[{x}, 2/3 - 4 Cos[x^2 + 1]^3,
  CompilationTarget -> "C"];
CompilePrint[f3]

(* Out:
    1 argument
    4 Integer registers
    4 Real registers
    Underflow checking off
    Overflow checking off
    Integer overflow checking on
    RuntimeAttributes -> {}

    R0 = A1
    I3 = 1
    I0 = 2
    I2 = 4
    I1 = 3
    Result = R1

1   R1 = I1
2   R2 = Reciprocal[ R1]
3   R1 = I0
4   R1 = R1 * R2
5   R2 = Square[ R0]
6   R3 = I3
7   R2 = R2 + R3
8   R3 = Cos[ R2]
9   R2 = Power[ R3, I1]
10  R3 = I2
11  R3 = R3 * R2
12  R2 = - R3
13  R1 = R1 + R2
14  Return
*)
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Related: The two "Edit" sections here mathematica.stackexchange.com/a/1101/5 –  rm -rf Feb 26 '13 at 14:35

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