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Fix fixed overflow when pathfinding across smallish maps

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This was SVN commit r7500.
This commit is contained in:
Ykkrosh 2010-05-03 19:12:42 +00:00
parent 646c218b2e
commit 04018773fd
1 changed files with 10 additions and 3 deletions
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13
source/simulation2/components/CCmpPathfinder.cpp
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@ -220,8 +220,8 @@ public:
REGISTER_COMPONENT_TYPE(Pathfinder)
const u32 g_CostPerTile = 256; // base cost to move between adjacent tiles
// Base cost to move between adjacent tiles
const u32 g_CostPerTile = 256;
/**
* Tile data for A* computation.
@ -500,7 +500,14 @@ static u32 CalculateHeuristic(u16 i, u16 j, u16 iGoal, u16 jGoal, u16 rGoal)
fixed rdist = dist - fixed::FromInt(rGoal);
rdist = rdist.Absolute();
return (rdist * (int)g_CostPerTile).ToInt_RoundToZero();
// To avoid overflows on large distances we have to convert to int before multiplying
// by the full tile cost, which means we lose some accuracy over short distances,
// so do a partial multiplication here.
// (This will overflow if sqrt(2)*tilesPerSide*premul >= 32768, so
// premul=32 means max tilesPerSide=724)
const int premul = 32;
cassert(g_CostPerTile % premul == 0);
return (rdist * premul).ToInt_RoundToZero() * (g_CostPerTile / premul);
#else
return (abs((int)i - (int)iGoal) + abs((int)j - (int)jGoal)) * g_CostPerTile;