Re: Compile
- To: mathgroup at smc.vnet.net
- Subject: [mg45280] Re: Compile
- From: Maxim <dontsendhere@.>
- Date: Sat, 27 Dec 2003 05:00:18 -0500 (EST)
- References: <bsd5h7$rb0$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Bill Rowe wrote:
> On 12/24/03 at 4:35 AM, dontsendhere@. (Maxim) wrote:
>
> > Not exactly. An elementary test shows that with both settings for Compiled the first
> > argument of Plot is evaluated in a non-standard way, as it should be (Mathematica Book,
> > A.4.2):
>
> > In[1]:=
> > Plot[Random[], {x, 0, 1}, Compiled -> True]
> > Plot[Random[], {x, 0, 1}, Compiled -> False]
>
> > (plots an irregular curve, not a straight line for one pre-evaluated value of Random[]).
>
> I don't see how this demonstrates your point. If you Compile an elementary (one pre-defined by Mathematica, i.e., not defined with Mathematica code) function I would expect no difference between the compiled and un-compiled versions. That is, I would expect the Mathematica interpreter to execucte some compiled code when it sees the token Random. And I would expect Compile to simply point to this compiled code.
>
> I would expect the only cases where Compile would make a difference is when the expression to be compiled is a sequence of operations defined by Mathematica code.
> --
> To reply via email subtract one hundred and four
My claim was: the first argument of Plot is evaluated in a non-standard way, that is, wrapping it in Evaluate would change the outcome. Do you not see how the example Plot[Random[],{x,0,1}] demonstrates this point? The argument that the effect of Compiled might change for some more complicated expressions is just speculation. I can make up a more complicated construct, like
Module[{y},
y[arg_] := Module[{ans}, ans = arg; ans += Random[]];
Plot[y[x], {x, 0, 1}]
]
How should Compiled 'make a difference' here? If you think that y[x] will be pre-evaluated, you're wrong.
Maxim Rytin
m.r at prontomail.com