[Freeciv-Dev] Re: warmap patch and gotohand

[Thue Janus Kristensen <thue@xxxxxxx>]

On Fri, 05 May 2000, Nicolas BRUNEL wrote:
> > But what abouT such places in the code as (advmillitary.c)
> > 
> >            c = (warmap.cost[bx][by] + m - 1) / m + 1 + 
> >                 warmap.seacost[x][y] / boatspeed; /* kluge */ 
> > 
> > Here the ai clearly have a movecostmap for both a boat and a unit at the
> > same time.
> 
> You're rigth it is used. But, is it initialized ?
> I changed the code a long time ago. Here the original code :
> 
> Index: gotohand.c
> ===================================================================
> RCS file: /home/freeciv/CVS/freeciv/server/gotohand.c,v
> retrieving revision 1.27
> retrieving revision 1.28
> diff -u -r1.27 -r1.28
> --- gotohand.c        1999/01/28 17:26:10     1.27
> +++ gotohand.c        1999/02/03 18:46:32     1.28
> @@ -65,25 +65,11 @@
>  
>  void init_warmap(int orig_x, int orig_y, enum unit_move_type which)
>  {
> -  int x, y, i, j;
> -  int maxcost = THRESHOLD * 6 + 2; /* should be big enough without being TOO 
> big */
> -  for (x = 0; x < map.xsize; x++) {
> -    if (x > orig_x)
> -      i = MIN(x - orig_x, orig_x + map.xsize - x);
> -    else
> -      i = MIN(orig_x - x, x + map.xsize - orig_x);      
> -    for (y = 0; y < map.ysize; y++) {
> -      if (y > orig_y)
> -        j = MAX(y - orig_y, i);
> -      else
> -        j = MAX(orig_y - y, i);
> -      j *= 3; /* can be speed up */
> -      if (j < maxcost) j = maxcost;
> -      if (j > 255) j = 255;
> -      if (which == LAND_MOVING) warmap.cost[x][y] = j; /* one if by land */
> -      else warmap.seacost[x][y] = j;
> -    }
> -  }
> +  int x, y;
> +  for (x = 0; x < map.xsize; x++) 
> +    for (y = 0; y < map.ysize; y++) 
> +      if (which == LAND_MOVING) warmap.cost[x][y] = 255; /* one if by land */
> +      else warmap.seacost[x][y] = 255;
>    if (which == LAND_MOVING) warmap.cost[orig_x][orig_y] = 0;
>    else warmap.seacost[orig_x][orig_y] = 0;
>  }  
> 
>    There was at the middle a square with value maxcost. Then, it was 
> real_map_distance * 3. It couldn't get bigger than 255. I though it was
> faster to set it to 255.
> 
> As you see for a land moving unit, the sea cost isn't initialized ! 

Well, thats the trick I guess. if you wanted to have a warmap of a
seaunit and a land unit at the same time, you would generate the warmap
for them one at a time. So you would
generate_warmap(seaunit)
generate_warmap((landunit)
If the seacost was initialized when the warmap for the land unit was
created the seaunit warmap would be deleted.

> Well, it isn't initialized here. Between generate_warmap and
> really_generate_warmap, seacost and cost is initialized. Usually, generate 
> warmap is called for a unit. Then really_generate_warmap is called for a
> ferryboat. It is done in find_something_to_kill and
> auto_settler_findwork. Many lines are shared between gotohand.c settlers.c
> and the ai code. So, yes, it's better to keep warmap.seacost
> untouched. With global variables, there is alway the risk to have a side
> effect.  
>  
>    To try to optimize the shortest path algorithm have a look at dijkstra 
> shortest path algorithm.
> 
> Bye and happy coding,

-Thue