From: ptkwt@... (Phil Tomson)
Date: 2005-07-22T05:40:57+09:00
Subject: Re: C extension makes things slower

In article <20050721175902.GH2279@tux-chan>,
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));
>}
>
 
Thanks, that's _MUCH_ (and consistently) faster:

  $ ruby point.rb
  Total time for pure ruby point test: 6.977688
  ACO_Ext initializing...
  Total time for extension point test: 2.777282


And now my real application that uses point is much faster too:
  $ruby TSP.rb
  -->best tour in gen 0: 8667.97295111485
  -->global best tour is: 8128.7749762166
  Total time: 3.635439

....used to be something like 22 seconds.

Oh, for the sake of complete documentation in case someone has similar 
questions in the future:

I had to add an allocate function so here's the new version of aco_ext.c:

//aco_ext.c
#include "ruby.h"
#include <math.h>
#include <stdio.h>

static int id_x;
static int id_y;
static int id_equal;

typedef struct {
        double x;
        double y;
} ACO_Point_Struct;

static void aco_point_free(void* p){
  free(p);
}

static VALUE aco_point_alloc(VALUE klass) {
  VALUE object;
  ACO_Point_Struct* point = (ACO_Point_Struct*)malloc(sizeof( 
ACO_Point_Struct));
  object = Data_Wrap_Struct(klass,0,aco_point_free,point);
  return object;
}

static VALUE aco_point_init(VALUE self, VALUE x, VALUE y){
  ACO_Point_Struct* _self ;
  //double x, y;
  Data_Get_Struct(self, ACO_Point_Struct, _self);
  _self->x = NUM2DBL(x);
  _self->y = NUM2DBL(y);
  return self;
}

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));
}

static VALUE aco_point_equal(VALUE self, VALUE other){
  ACO_Point_Struct *_self;
  ACO_Point_Struct *_other;
  double x, y;
  Data_Get_Struct(self, ACO_Point_Struct, _self);
  Data_Get_Struct(other, ACO_Point_Struct, _other); 
  return((_self->x == _other->x) && (_self->y == _other->y));
}

VALUE cACOMod;
VALUE cACOPoint;
VALUE cACOGraph;

void Init_ACO_Ext() {
  printf("ACO_Ext initializing...\n");
  cACOMod = rb_define_module("ACO");
  cACOPoint = rb_define_class_under(cACOMod,"Point",rb_cObject);
  cACOGraph = rb_define_class_under(cACOMod,"Graph",rb_cObject);
  rb_define_alloc_func(cACOPoint, aco_point_alloc);
  rb_define_method(cACOPoint,"initialize",aco_point_init,2);
  rb_define_method(cACOPoint,"-",aco_point_diff,1);
  rb_define_method(cACOPoint,"==",aco_point_equal,1);
    
  id_x      = rb_intern("x");
  id_y      = rb_intern("y");
  id_equal  = rb_intern("==");
}
//end aco_ext.c


Phil