demands.cpp

00001 /* $Id$ */
00002 
00003 /*
00004  * This file is part of OpenTTD.
00005  * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
00006  * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
00007  * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
00008  */
00009 
00012 #include "demands.h"
00013 #include "../station_base.h"
00014 #include "../settings_type.h"
00015 #include "../newgrf_cargo.h"
00016 #include "../cargotype.h"
00017 #include "../core/math_func.hpp"
00018 #include <list>
00019 
00020 typedef std::list<NodeID> NodeList;
00021 
00030 void SymmetricScaler::SetDemands(LinkGraphComponent * graph, NodeID from_id, NodeID to_id, uint demand_forw)
00031 {
00032   if (graph->GetNode(from_id).demand > 0) {
00033     uint demand_back = demand_forw * this->mod_size / 100;
00034     uint undelivered = graph->GetNode(to_id).undelivered_supply;
00035     if (demand_back > undelivered) {
00036       demand_back = undelivered;
00037       demand_forw = max(1U, demand_back * 100 / this->mod_size);
00038     }
00039     this->Scaler::SetDemands(graph, to_id, from_id, demand_back);
00040   }
00041 
00042   this->Scaler::SetDemands(graph, from_id, to_id, demand_forw);
00043 }
00044 
00053 FORCEINLINE void Scaler::SetDemands(LinkGraphComponent * graph, NodeID from_id, NodeID to_id, uint demand_forw)
00054 {
00055   Edge &forward = graph->GetEdge(from_id, to_id);
00056   forward.demand += demand_forw;
00057   forward.unsatisfied_demand += demand_forw;
00058   graph->GetNode(from_id).undelivered_supply -= demand_forw;
00059 }
00060 
00065 template<class Tscaler>
00066 void DemandCalculator::CalcDemand(LinkGraphComponent *graph, Tscaler scaler)
00067 {
00068   NodeList supplies;
00069   NodeList demands;
00070   uint num_supplies = 0;
00071   uint num_demands = 0;
00072 
00073   for(NodeID node = 0; node < graph->GetSize(); node++) {
00074     Node &n = graph->GetNode(node);
00075     scaler.AddNode(n);
00076     if (n.supply > 0) {
00077       supplies.push_back(node);
00078       num_supplies++;
00079     }
00080     if (n.demand > 0) {
00081       demands.push_back(node);
00082       num_demands++;
00083     }
00084   }
00085 
00086   if (num_supplies == 0 || num_demands == 0) return;
00087 
00088   /* mean acceptance attributed to each node. If the distribution is
00089    * symmetric this is relative to remote supply, otherwise it is
00090    * relative to remote demand.
00091    */
00092   scaler.SetDemandPerNode(num_demands);
00093   uint chance = 0;
00094 
00095   while(!supplies.empty() && !demands.empty()) {
00096     NodeID node1 = supplies.front();
00097     supplies.pop_front();
00098 
00099     Node &from = graph->GetNode(node1);
00100 
00101     for(uint i = 0; i < num_demands; ++i) {
00102       assert(!demands.empty());
00103       NodeID node2 = demands.front();
00104       demands.pop_front();
00105       if (node1 == node2) {
00106         if (demands.empty() && supplies.empty()) {
00107           /* only one node with supply and demand left */
00108           return;
00109         } else {
00110           demands.push_back(node2);
00111           continue;
00112         }
00113       }
00114       Node &to = graph->GetNode(node2);
00115 
00116       int32 supply = scaler.EffectiveSupply(from, to);
00117       assert(supply > 0);
00118 
00119       /* scale the distance by mod_dist around max_distance */
00120       int32 distance = this->max_distance - (this->max_distance -
00121           (int32)graph->GetEdge(node1, node2).distance) * this->mod_dist / 100;
00122 
00123       /* scale the accuracy by distance around accuracy / 2 */
00124       int32 divisor = this->accuracy * (this->mod_dist - 50) / 100 +
00125           this->accuracy * distance / this->max_distance + 1;
00126 
00127       assert(divisor > 0);
00128 
00129       uint demand_forw = 0;
00130       if (divisor <= supply) {
00131         /* at first only distribute demand if
00132          * effective supply / accuracy divisor >= 1
00133          * Others are too small or too far away to be considered.
00134          */
00135         demand_forw = supply / divisor;
00136       } else if (++chance > this->accuracy * num_demands * num_supplies) {
00137         /* After some trying, if there is still supply left, distribute
00138          * demand also to other nodes.
00139          */
00140         demand_forw = 1;
00141       }
00142 
00143       demand_forw = min(demand_forw, from.undelivered_supply);
00144 
00145       scaler.SetDemands(graph, node1, node2, demand_forw);
00146 
00147       if (scaler.DemandLeft(to)) {
00148         demands.push_back(node2);
00149       } else {
00150         num_demands--;
00151       }
00152 
00153       if (from.undelivered_supply == 0) break;
00154 
00155     }
00156     if (from.undelivered_supply != 0) {
00157       supplies.push_back(node1);
00158     } else {
00159       num_supplies--;
00160     }
00161   }
00162 }
00163 
00168 DemandCalculator::DemandCalculator(LinkGraphComponent *graph) :
00169   max_distance(MapSizeX() + MapSizeY() + 1)
00170 {
00171   CargoID cargo = graph->GetCargo();
00172   const LinkGraphSettings &settings = graph->GetSettings();
00173 
00174   this->accuracy = settings.accuracy;
00175   this->mod_dist = settings.demand_distance;
00176   if (this->mod_dist > 100) {
00177     /* increase effect of mod_dist > 100 */
00178     int over100 = this->mod_dist - 100;
00179     this->mod_dist = 100 + over100 * over100;
00180   }
00181 
00182   switch (settings.GetDistributionType(cargo)) {
00183   case DT_SYMMETRIC:
00184     this->CalcDemand<SymmetricScaler>(graph, SymmetricScaler(settings.demand_size));
00185     break;
00186   case DT_ASYMMETRIC:
00187     this->CalcDemand<AsymmetricScaler>(graph, AsymmetricScaler());
00188     break;
00189   default:
00190     NOT_REACHED();
00191   }
00192 }