From: Joe Van Dyk <joevandyk@...>
Date: 2005-07-22T04:01:10+09:00
Subject: Re: C extension makes things slower

On 7/21/05, Mauricio Fern�ndez <mfp@acm.org> wrote:
> On Fri, Jul 22, 2005 at 02:05:56AM +0900, Phil Tomson wrote:
> > In article <42DF4F1D.2060607@capitain.de>,
> > Pit Capitain  <pit@capitain.de> wrote:
> > >Phil Tomson schrieb:
> > >> And the results:
> > >> l% ruby point.rb
> > >>   Total time for pure ruby point test: 8.600752
> > >>   ACO_Ext initializing...
> > >>   Total time for extension point test: 6.086567
> > However, here's the result of another run:
> >
> >   Total time for pure ruby point test: 8.051388
> >   ACO_Ext initializing...
> >   Total time for extension point test: 9.212984
> 
> You're doing things like
> 
> static VALUE aco_point_diff(VALUE self, VALUE other){
>   double self_x = NUM2DBL(rb_iv_get(self, "@x"));
>   double self_y = NUM2DBL(rb_iv_get(self, "@y"));
>   double other_x= NUM2DBL(rb_iv_get(other, "@x"));
>   double other_y= NUM2DBL(rb_iv_get(other, "@y"));
>   double xdiffsq= pow( (self_x - other_x),2 );
>   double ydiffsq= pow( (self_y - other_y),2 );
>   return rb_float_new(sqrt( xdiffsq  +  ydiffsq ) );
> 
> }
> 
> when you probably want something resembling
> 
> typedef struct {
>         double x;
>         double y;
> } ACO_Point_Struct;
> 
> static VALUE
> aco_point_diff(VALUE self, VALUE other)
> {
>   ACO_Point_Struct *_self, *_other;
>   double dx, dy;
> 
>   Data_Get_Struct(self, ACO_Point_Struct, _self);
>   Data_Get_Struct(other, ACO_Point_Struct, _other);
> 
>   dx = _self->x - _other->x;
>   dy = _self->y - _other->y;
>   return rb_float_new(sqrt(dx * dx + dy * dy));
> }
> 

Wow, neat.  Does Data_Get_Struct extract out members of a Ruby object
and assign them to corresponding members of a C struct?