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(svn r16652) -Codechange: use less strict, but faster check for quickly bailing out in FindTrainCollideEnum() (Bilbo) 

-Codechange: shuffle the code a bit
release/1.0
smatz 2009-06-24 23:59:20 +00:00
parent d45b27c46b
commit 029fb9bdee
1 changed files with 35 additions and 32 deletions
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63
src/train_cmd.cpp
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@ -3530,6 +3530,16 @@ static uint CountPassengersInTrain(const Train *v)
*/
static uint TrainCrashed(Train *v)
{
/* Try to re-reserve track under already crashed train too */
for (const Train *u = v; u != NULL; u = u->Next()) {
TrackBits trackbits = u->track;
if (trackbits == TRACK_BIT_WORMHOLE) {
/* Vehicle is inside a wormhole, v->track contains no useful value then. */
trackbits = DiagDirToDiagTrackBits(GetTunnelBridgeDirection(u->tile));
}
TryReserveRailTrack(u->tile, TrackBitsToTrack(trackbits));
}
/* do not crash train twice */
if (v->vehstatus & VS_CRASHED) return 0;
@ -3543,51 +3553,44 @@ static uint TrainCrashed(Train *v)
}
struct TrainCollideChecker {
Vehicle *v; ///< vehicle we are testing for collision
uint num; ///< number of dead if train collided
Train *v; ///< vehicle we are testing for collision
uint num; ///< number of victims if train collided
};
static Vehicle *FindTrainCollideEnum(Vehicle *v, void *data)
{
TrainCollideChecker *tcc = (TrainCollideChecker*)data;
if (v->type != VEH_TRAIN) return NULL;
/* not a train or in depot */
if (v->type != VEH_TRAIN || Train::From(v)->track == TRACK_BIT_DEPOT) return NULL;
/* get first vehicle now to make most usual checks faster */
Vehicle *coll = v->First();
Train *coll = Train::From(v)->First();
/* can't collide with own wagons */
if (coll == tcc->v) return NULL;
/* can't collide with own wagons && can't crash in depot && the same height level */
if (coll != tcc->v && Train::From(v)->track != TRACK_BIT_DEPOT && abs(v->z_pos - tcc->v->z_pos) < 6) {
int x_diff = v->x_pos - tcc->v->x_pos;
int y_diff = v->y_pos - tcc->v->y_pos;
/* Needed to disable possible crash of competitor train in station by building diagonal track at its end.
* The second check is false when (abs(first), abs(second)) is: a) 5, 0 b) 4, <=3 c) 3, <=4, d) 2-, <=5
* Sum of these two is at most 2 + 5 == 4 + 3 == 7. So we can just test if sum of abs() is > 7 to prevent
* multiplying. Simply, when sum of abs() is >= 8, the sum of squares can't be <= 25.
* Even gcc3.4 seems to do abs() branchless (using arithmetics or conditional moves). */
if (abs(x_diff) + abs(y_diff) > 7 || x_diff * x_diff + y_diff * y_diff > 25) return NULL;
/* Do fast calculation to check whether trains are not in close vicinity
* and quickly reject trains distant enough for any collision.
* Differences are shifted by 7, mapping range [-7 .. 8] into [0 .. 15]
* Differences are then ORed and then we check for any higher bits */
uint hash = (y_diff + 7) | (x_diff + 7);
if (hash & ~15) return NULL;
/* Slower check using multiplication */
if (x_diff * x_diff + y_diff * y_diff > 25) return NULL;
/* Happens when there is a train under bridge next to bridge head */
if (abs(v->z_pos - tcc->v->z_pos) > 5) return NULL;
/* crash both trains */
tcc->num += TrainCrashed(Train::From(tcc->v));
tcc->num += TrainCrashed(Train::From(coll));
tcc->num += TrainCrashed(tcc->v);
tcc->num += TrainCrashed(coll);
/* Try to reserve all tiles directly under the crashed trains.
* As there might be more than two trains involved, we have to do that for all vehicles */
const Train *u;
FOR_ALL_TRAINS(u) {
if ((u->vehstatus & VS_CRASHED) && u->track != TRACK_BIT_DEPOT) {
TrackBits trackbits = u->track;
if (trackbits == TRACK_BIT_WORMHOLE) {
/* Vehicle is inside a wormhole, v->track contains no useful value then. */
trackbits = DiagDirToDiagTrackBits(GetTunnelBridgeDirection(u->tile));
}
TryReserveRailTrack(u->tile, TrackBitsToTrack(trackbits));
}
}
}
return NULL;
return NULL; // continue searching
}
/**