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(svn r14417) -Codechange: rewrite GetClosestWaterDistance(), now it is ~100 times faster than pre-r14416 in average case

This commit is contained in:
smatz 2008-09-29 18:56:36 +00:00
parent e65771f25c
commit a858d0993f
1 changed files with 40 additions and 26 deletions
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66
src/newgrf_industries.cpp
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@ -45,41 +45,55 @@ IndustryType MapNewGRFIndustryType(IndustryType grf_type, uint32 grf_id)
* Finds the distance for the closest tile with water/land given a tile
* @param tile the tile to find the distance too
* @param water whether to find water or land
* @return distance to nearest water (max 0x7F) / land (max 0x1FF; 0x200 if there is no land)
* @note FAILS when an industry should be seen as water
*/
static uint GetClosestWaterDistance(TileIndex tile, bool water)
{
TileIndex t;
int best_dist;
for (t = 0; t < MapSize(); t++) {
if (!IsTileType(t, MP_VOID) && IsTileType(t, MP_WATER) == water) break;
}
if (t == MapSize() && !water) return 0x200;
best_dist = DistanceManhattan(tile, t);
if (IsTileType(tile, MP_WATER) == water) return 0;
for (; t < MapSize(); t++) {
int dist = DistanceManhattan(tile, t);
if (dist < best_dist) {
if (!IsTileType(t, MP_VOID) && IsTileType(t, MP_WATER) == water) best_dist = dist;
} else {
/* When the Y distance between the current row and the 'source' tile
* is larger than the best distance, we've found the best distance */
if ((int)TileY(t) - (int)TileY(tile) > best_dist) break;
if ((int)TileX(t) - (int)TileX(tile) > best_dist) {
/* We can safely skip this many tiles; from here all tiles have a
* higher or equal distance than the best distance */
t |= MapMaxX();
continue;
} else if (TileX(tile) < TileX(t)) {
/* We can safely skip this many tiles; up to here all tiles have a
* higher or equal distance than the best distance */
t += dist - best_dist;
continue;
uint max_dist = water ? 0x7F : 0x200;
int x = TileX(tile);
int y = TileY(tile);
uint max_x = MapMaxX();
uint max_y = MapMaxY();
/* go in a 'spiral' with increasing manhattan distance in each iteration */
for (uint dist = 1; dist < max_dist; dist++) {
/* next 'diameter' */
y--;
/* going counter-clockwise around this square */
for (DiagDirection dir = DIAGDIR_BEGIN; dir < DIAGDIR_END; dir++) {
static const int8 ddx[DIAGDIR_END] = { -1, 1, 1, -1};
static const int8 ddy[DIAGDIR_END] = { 1, 1, -1, -1};
int dx = ddx[dir];
int dy = ddy[dir];
/* each side of this square has length 'dist' */
for (uint a = 0; a < dist; a++) {
/* MP_VOID tiles are not checked (interval is [0; max) for IsInsideMM())*/
if (IsInsideMM(x, 0, max_x) && IsInsideMM(y, 0, max_y)) {
TileIndex t = TileXY(x, y);
if (IsTileType(t, MP_WATER) == water) return dist;
}
x += dx;
y += dy;
}
}
}
return min(best_dist, water ? 0x7F : 0x1FF);
if (!water) {
/* no land found - is this a water-only map? */
for (TileIndex t = 0; t < MapSize(); t++) {
if (!IsTileType(t, MP_VOID) && !IsTileType(t, MP_WATER)) return 0x1FF;
}
}
return max_dist;
}
/** Make an analysis of a tile and check for its belonging to the same