Re: Compile a Module
- To: mathgroup at smc.vnet.net
- Subject: [mg83172] Re: Compile a Module
- From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
- Date: Tue, 13 Nov 2007 07:02:27 -0500 (EST)
- Organization: Uni Leipzig
- References: <fhbnuc$r4s$1@smc.vnet.net>
- Reply-to: kuska at informatik.uni-leipzig.de
Hi,
cAlongAway =
Compile[{{tip, _Real, 1}, {end, _Real, 1}, {calc, _Real, 1}},
Module[{mid, r, theta},
mid = (tip + end)/2;
r = Sqrt[Dot[calc - mid, calc - mid]];
theta = VectorAngle[calc - mid, end - mid];
{r Cos[theta], r Sin[theta]}]]
??
but you see when you look ino the compiled code
there is still the call to VectorAngle[] and usual such
a call degrade the execution speed of the
compiled function.
Regards
Jens
JOHN ERB wrote:
> Can the following module be compiled?
> It needs to be used 10^4 times in my program.
> It is used to calculate the distance parallel and perpendicular
> to the midpoint of 2D line segment with reference to a point of interest (calc).
>
> AlongAway[{tip_,end_,calc_}]:=Module[{mid,r,theta,along,away},
> mid=(tip+end)/2;
> r=Sqrt[Dot[calc-mid,calc-mid]];
> theta=VectorAngle[calc-mid,end-mid];
> along=r Cos[theta];
> away=r Sin[theta];
> {along,away}]
>
> AlongAway[{{-1, 0}, {1, 0}, {2, 1}}]
> (* answer is {2,1} *)
>
> (* the code below does not seem to work *)
> cAlongAway=Compile[{{tip,_Real},{end,_Real},{calc,_Real}},AlongAway]
>
> John C. Erb
>