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Change: Use bitmap for free unit ID generation. (#12165)

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This improves performance of finding the next free unit number for a vehicle.

Based loosely on pool's used slot bitmap.
This commit is contained in:
Peter Nelson
2024-02-25 12:36:13 +00:00
committed by GitHub
parent 8afef45d4e
commit 56cf89d189
7 changed files with 68 additions and 56 deletions
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72
src/vehicle.cpp
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@@ -846,6 +846,8 @@ void Vehicle::PreDestructor()
DeleteGroupHighlightOfVehicle(this);
}
Company::Get(this->owner)->freeunits[this->type].ReleaseID(this->unitnumber);
if (this->type == VEH_AIRCRAFT && this->IsPrimaryVehicle()) {
Aircraft *a = Aircraft::From(this);
Station *st = GetTargetAirportIfValid(a);
@@ -1816,44 +1818,50 @@ VehicleEnterTileStatus VehicleEnterTile(Vehicle *v, TileIndex tile, int x, int y
}
/**
* Initializes the structure. Vehicle unit numbers are supposed not to change after
* struct initialization, except after each call to this->NextID() the returned value
* is assigned to a vehicle.
* @param type type of vehicle
* @param owner owner of vehicles
* Find first unused unit number.
* This does not mark the unit number as used.
* @returns First unused unit number.
*/
FreeUnitIDGenerator::FreeUnitIDGenerator(VehicleType type, CompanyID owner) : cache(nullptr), maxid(0), curid(0)
UnitID FreeUnitIDGenerator::NextID() const
{
/* Find maximum */
for (const Vehicle *v : Vehicle::Iterate()) {
if (v->type == type && v->owner == owner) {
this->maxid = std::max<UnitID>(this->maxid, v->unitnumber);
}
}
if (this->maxid == 0) return;
/* Reserving 'maxid + 2' because we need:
* - space for the last item (with v->unitnumber == maxid)
* - one free slot working as loop terminator in FreeUnitIDGenerator::NextID() */
this->cache = CallocT<bool>(this->maxid + 2);
/* Fill the cache */
for (const Vehicle *v : Vehicle::Iterate()) {
if (v->type == type && v->owner == owner) {
this->cache[v->unitnumber] = true;
}
for (auto it = std::begin(this->used_bitmap); it != std::end(this->used_bitmap); ++it) {
BitmapStorage available = ~(*it);
if (available == 0) continue;
return static_cast<UnitID>(std::distance(std::begin(this->used_bitmap), it) * BITMAP_SIZE + FindFirstBit(available) + 1);
}
return static_cast<UnitID>(this->used_bitmap.size() * BITMAP_SIZE + 1);
}
/** Returns next free UnitID. Supposes the last returned value was assigned to a vehicle. */
UnitID FreeUnitIDGenerator::NextID()
/**
* Use a unit number. If the unit number is not valid it is ignored.
* @param index Unit number to use.
* @returns Unit number used.
*/
UnitID FreeUnitIDGenerator::UseID(UnitID index)
{
if (this->maxid <= this->curid) return ++this->curid;
if (index == 0 || index == UINT16_MAX) return index;
while (this->cache[++this->curid]) { } // it will stop, we reserved more space than needed
index--;
return this->curid;
size_t slot = index / BITMAP_SIZE;
if (slot >= this->used_bitmap.size()) this->used_bitmap.resize(slot + 1);
SetBit(this->used_bitmap[index / BITMAP_SIZE], index % BITMAP_SIZE);
return index + 1;
}
/**
* Release a unit number. If the unit number is not valid it is ignored.
* @param index Unit number to release.
*/
void FreeUnitIDGenerator::ReleaseID(UnitID index)
{
if (index == 0 || index == UINT16_MAX) return;
index--;
assert(index / BITMAP_SIZE < this->used_bitmap.size());
ClrBit(this->used_bitmap[index / BITMAP_SIZE], index % BITMAP_SIZE);
}
/**
@@ -1876,9 +1884,7 @@ UnitID GetFreeUnitNumber(VehicleType type)
const Company *c = Company::Get(_current_company);
if (c->group_all[type].num_vehicle >= max_veh) return UINT16_MAX; // Currently already at the limit, no room to make a new one.
FreeUnitIDGenerator gen(type, _current_company);
return gen.NextID();
return c->freeunits[type].NextID();
}