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(svn r25423) -Fix: integer overflows in MCF solver

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fonsinchen 2013-06-17 20:37:31 +00:00
parent d9985c3331
commit b923eb31a8
1 changed files with 14 additions and 4 deletions
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18
src/linkgraph/linkgraphjob.h
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@ -351,14 +351,14 @@ public:
/**
* Get ratio of free * 16 (so that we get fewer 0) /
* total capacity + 1 (so that we don't divide by 0).
* max(total capacity, 1) (so that we don't divide by 0).
* @param free Free capacity.
* @param total Total capacity.
* @return free * 16 / (total + 1).
* @return free * 16 / max(total, 1).
*/
inline static int GetCapacityRatio(int free, int total)
inline static int GetCapacityRatio(int free, uint total)
{
return (free << 4) / (total + 1);
return Clamp(free, PATH_CAP_MIN_FREE, PATH_CAP_MAX_FREE) * PATH_CAP_MULTIPLIER / max(total, 1U);
}
/**
@ -400,6 +400,16 @@ public:
void Fork(Path *base, uint cap, int free_cap, uint dist);
protected:
/**
* Some boundaries to clamp agains in order to avoid integer overflows.
*/
enum PathCapacityBoundaries {
PATH_CAP_MULTIPLIER = 16,
PATH_CAP_MIN_FREE = (INT_MIN + 1) / PATH_CAP_MULTIPLIER,
PATH_CAP_MAX_FREE = (INT_MAX - 1) / PATH_CAP_MULTIPLIER
};
uint distance; ///< Sum(distance of all legs up to this one).
uint capacity; ///< This capacity is min(capacity) fom all edges.
int free_capacity; ///< This capacity is min(edge.capacity - edge.flow) for the current run of Dijkstra.