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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 * Finds the distance for the closest tile with water/land given a tile
* @param tile the tile to find the distance too * @param tile the tile to find the distance too
* @param water whether to find water or land * @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 * @note FAILS when an industry should be seen as water
*/ */
static uint GetClosestWaterDistance(TileIndex tile, bool water) static uint GetClosestWaterDistance(TileIndex tile, bool water)
{ {
TileIndex t; if (IsTileType(tile, MP_WATER) == water) return 0;
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);
for (; t < MapSize(); t++) { uint max_dist = water ? 0x7F : 0x200;
int dist = DistanceManhattan(tile, t);
if (dist < best_dist) { int x = TileX(tile);
if (!IsTileType(t, MP_VOID) && IsTileType(t, MP_WATER) == water) best_dist = dist; int y = TileY(tile);
} else {
/* When the Y distance between the current row and the 'source' tile uint max_x = MapMaxX();
* is larger than the best distance, we've found the best distance */ uint max_y = MapMaxY();
if ((int)TileY(t) - (int)TileY(tile) > best_dist) break;
if ((int)TileX(t) - (int)TileX(tile) > best_dist) { /* go in a 'spiral' with increasing manhattan distance in each iteration */
/* We can safely skip this many tiles; from here all tiles have a for (uint dist = 1; dist < max_dist; dist++) {
* higher or equal distance than the best distance */ /* next 'diameter' */
t |= MapMaxX(); y--;
continue;
} else if (TileX(tile) < TileX(t)) { /* going counter-clockwise around this square */
/* We can safely skip this many tiles; up to here all tiles have a for (DiagDirection dir = DIAGDIR_BEGIN; dir < DIAGDIR_END; dir++) {
* higher or equal distance than the best distance */ static const int8 ddx[DIAGDIR_END] = { -1, 1, 1, -1};
t += dist - best_dist; static const int8 ddy[DIAGDIR_END] = { 1, 1, -1, -1};
continue;
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 /** Make an analysis of a tile and check for its belonging to the same