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* This file is part of OpenTTD.
* 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.
* 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.
* 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/>.
*/
/** @file yapf_base.hpp Base classes for YAPF. */
#ifndef YAPF_BASE_HPP
#define YAPF_BASE_HPP
#include "../../debug.h"
#include "../../settings_type.h"
/**
* CYapfBaseT - A-star type path finder base class.
* Derive your own pathfinder from it. You must provide the following template argument:
* Types - used as collection of local types used in pathfinder
*
* Requirements for the Types struct:
* ----------------------------------
* The following types must be defined in the 'Types' argument:
* - Types::Tpf - your pathfinder derived from CYapfBaseT
* - Types::NodeList - open/closed node list (look at CNodeList_HashTableT)
* NodeList needs to have defined local type Titem - defines the pathfinder node type.
* Node needs to define local type Key - the node key in the collection ()
*
* For node list you can use template class CNodeList_HashTableT, for which
* you need to declare only your node type. Look at test_yapf.h for an example.
*
*
* Requirements to your pathfinder class derived from CYapfBaseT:
* --------------------------------------------------------------
* Your pathfinder derived class needs to implement following methods:
* inline void PfSetStartupNodes()
* inline void PfFollowNode(Node &org)
* inline bool PfCalcCost(Node &n)
* inline bool PfCalcEstimate(Node &n)
* inline bool PfDetectDestination(Node &n)
*
* For more details about those methods, look at the end of CYapfBaseT
* declaration. There are some examples. For another example look at
* test_yapf.h (part or unittest project).
*/
template <class Types>
class CYapfBaseT {
public:
typedef typename Types::Tpf Tpf; ///< the pathfinder class (derived from THIS class)
typedef typename Types::TrackFollower TrackFollower;
typedef typename Types::NodeList NodeList; ///< our node list
typedef typename Types::VehicleType VehicleType; ///< the type of vehicle
typedef typename NodeList::Titem Node; ///< this will be our node type
typedef typename Node::Key Key; ///< key to hash tables
NodeList m_nodes; ///< node list multi-container
protected:
Node *m_pBestDestNode; ///< pointer to the destination node found at last round
Node *m_pBestIntermediateNode; ///< here should be node closest to the destination if path not found
const YAPFSettings *m_settings; ///< current settings (_settings_game.yapf)
int m_max_search_nodes; ///< maximum number of nodes we are allowed to visit before we give up
const VehicleType *m_veh; ///< vehicle that we are trying to drive
int m_stats_cost_calcs; ///< stats - how many node's costs were calculated
int m_stats_cache_hits; ///< stats - how many node's costs were reused from cache
public:
int m_num_steps; ///< this is there for debugging purposes (hope it doesn't hurt)
public:
/** default constructor */
inline CYapfBaseT()
: m_pBestDestNode(nullptr)
, m_pBestIntermediateNode(nullptr)
, m_settings(&_settings_game.pf.yapf)
, m_max_search_nodes(PfGetSettings().max_search_nodes)
, m_veh(nullptr)
, m_stats_cost_calcs(0)
, m_stats_cache_hits(0)
, m_num_steps(0)
{
}
/** default destructor */
~CYapfBaseT() {}
protected:
/** to access inherited path finder */
inline Tpf& Yapf()
{
return *static_cast<Tpf *>(this);
}
public:
/** return current settings (can be custom - company based - but later) */
inline const YAPFSettings& PfGetSettings() const
{
return *m_settings;
}
/**
* Main pathfinder routine:
* - set startup node(s)
* - main loop that stops if:
* - the destination was found
* - or the open list is empty (no route to destination).
* - or the maximum amount of loops reached - m_max_search_nodes (default = 10000)
* @return true if the path was found
*/
inline bool FindPath(const VehicleType *v)
{
m_veh = v;
Yapf().PfSetStartupNodes();
bool bDestFound = true;
for (;;) {
m_num_steps++;
Node *n = m_nodes.GetBestOpenNode();
if (n == nullptr) {
break;
}
/* if the best open node was worse than the best path found, we can finish */
if (m_pBestDestNode != nullptr && m_pBestDestNode->GetCost() < n->GetCostEstimate()) {
break;
}
Yapf().PfFollowNode(*n);
if (m_max_search_nodes == 0 || m_nodes.ClosedCount() < m_max_search_nodes) {
m_nodes.PopOpenNode(n->GetKey());
m_nodes.InsertClosedNode(*n);
} else {
bDestFound = false;
break;
}
}
bDestFound &= (m_pBestDestNode != nullptr);
if (_debug_yapf_level >= 3) {
UnitID veh_idx = (m_veh != nullptr) ? m_veh->unitnumber : 0;
char ttc = Yapf().TransportTypeChar();
float cache_hit_ratio = (m_stats_cache_hits == 0) ? 0.0f : ((float)m_stats_cache_hits / (float)(m_stats_cache_hits + m_stats_cost_calcs) * 100.0f);
int cost = bDestFound ? m_pBestDestNode->m_cost : -1;
int dist = bDestFound ? m_pBestDestNode->m_estimate - m_pBestDestNode->m_cost : -1;
Debug(yapf, 3, "[YAPF{}]{}{:4d} - {} rounds - {} open - {} closed - CHR {:4.1f}% - C {} D {}",
ttc, bDestFound ? '-' : '!', veh_idx, m_num_steps, m_nodes.OpenCount(), m_nodes.ClosedCount(), cache_hit_ratio, cost, dist
);
}
return bDestFound;
}
/**
* If path was found return the best node that has reached the destination. Otherwise
* return the best visited node (which was nearest to the destination).
*/
inline Node *GetBestNode()
{
return (m_pBestDestNode != nullptr) ? m_pBestDestNode : m_pBestIntermediateNode;
}
/**
* Calls NodeList::CreateNewNode() - allocates new node that can be filled and used
* as argument for AddStartupNode() or AddNewNode()
*/
inline Node& CreateNewNode()
{
Node &node = *m_nodes.CreateNewNode();
return node;
}
/** Add new node (created by CreateNewNode and filled with data) into open list */
inline void AddStartupNode(Node &n)
{
Yapf().PfNodeCacheFetch(n);
/* insert the new node only if it is not there */
if (m_nodes.FindOpenNode(n.m_key) == nullptr) {
m_nodes.InsertOpenNode(n);
} else {
/* if we are here, it means that node is already there - how it is possible?
* probably the train is in the position that both its ends point to the same tile/exit-dir
* very unlikely, but it happened */
}
}
/** add multiple nodes - direct children of the given node */
inline void AddMultipleNodes(Node *parent, const TrackFollower &tf)
{
bool is_choice = (KillFirstBit(tf.m_new_td_bits) != TRACKDIR_BIT_NONE);
for (TrackdirBits rtds = tf.m_new_td_bits; rtds != TRACKDIR_BIT_NONE; rtds = KillFirstBit(rtds)) {
Trackdir td = (Trackdir)FindFirstBit2x64(rtds);
Node &n = Yapf().CreateNewNode();
n.Set(parent, tf.m_new_tile, td, is_choice);
Yapf().AddNewNode(n, tf);
}
}
/**
* In some cases an intermediate node branch should be pruned.
* The most prominent case is when a red EOL signal is encountered, but
* there was a segment change (e.g. a rail type change) before that. If
* the branch would not be pruned, the rail type change location would
* remain the best intermediate node, and thus the vehicle would still
* go towards the red EOL signal.
*/
void PruneIntermediateNodeBranch(Node *n)
{
bool intermediate_on_branch = false;
while (n != nullptr && (n->m_segment->m_end_segment_reason & ESRB_CHOICE_FOLLOWS) == 0) {
if (n == Yapf().m_pBestIntermediateNode) intermediate_on_branch = true;
n = n->m_parent;
}
if (intermediate_on_branch) Yapf().m_pBestIntermediateNode = n;
}
/**
* AddNewNode() - called by Tderived::PfFollowNode() for each child node.
* Nodes are evaluated here and added into open list
*/
void AddNewNode(Node &n, const TrackFollower &tf)
{
/* evaluate the node */
bool bCached = Yapf().PfNodeCacheFetch(n);
if (!bCached) {
m_stats_cost_calcs++;
} else {
m_stats_cache_hits++;
}
bool bValid = Yapf().PfCalcCost(n, &tf);
if (bCached) {
Yapf().PfNodeCacheFlush(n);
}
if (bValid) bValid = Yapf().PfCalcEstimate(n);
/* have the cost or estimate callbacks marked this node as invalid? */
if (!bValid) return;
/* detect the destination */
bool bDestination = Yapf().PfDetectDestination(n);
if (bDestination) {
if (m_pBestDestNode == nullptr || n < *m_pBestDestNode) {
m_pBestDestNode = &n;
}
m_nodes.FoundBestNode(n);
return;
}
/* The new node can be set as the best intermediate node only once we're
* certain it will be finalized by being inserted into the open list. */
bool set_intermediate = m_max_search_nodes > 0 && (m_pBestIntermediateNode == nullptr || (m_pBestIntermediateNode->GetCostEstimate() - m_pBestIntermediateNode->GetCost()) > (n.GetCostEstimate() - n.GetCost()));
/* check new node against open list */
Node *openNode = m_nodes.FindOpenNode(n.GetKey());
if (openNode != nullptr) {
/* another node exists with the same key in the open list
* is it better than new one? */
if (n.GetCostEstimate() < openNode->GetCostEstimate()) {
/* update the old node by value from new one */
m_nodes.PopOpenNode(n.GetKey());
*openNode = n;
/* add the updated old node back to open list */
m_nodes.InsertOpenNode(*openNode);
if (set_intermediate) m_pBestIntermediateNode = openNode;
}
return;
}
/* check new node against closed list */
Node *closedNode = m_nodes.FindClosedNode(n.GetKey());
if (closedNode != nullptr) {
/* another node exists with the same key in the closed list
* is it better than new one? */
int node_est = n.GetCostEstimate();
int closed_est = closedNode->GetCostEstimate();
if (node_est < closed_est) {
/* If this assert occurs, you have probably problem in
* your Tderived::PfCalcCost() or Tderived::PfCalcEstimate().
* The problem could be:
* - PfCalcEstimate() gives too large numbers
* - PfCalcCost() gives too small numbers
* - You have used negative cost penalty in some cases (cost bonus) */
NOT_REACHED();
}
return;
}
/* the new node is really new
* add it to the open list */
m_nodes.InsertOpenNode(n);
if (set_intermediate) m_pBestIntermediateNode = &n;
}
const VehicleType * GetVehicle() const
{
return m_veh;
}
void DumpBase(DumpTarget &dmp) const
{
dmp.WriteStructT("m_nodes", &m_nodes);
dmp.WriteValue("m_num_steps", m_num_steps);
}
/* methods that should be implemented at derived class Types::Tpf (derived from CYapfBaseT) */
#if 0
/** Example: PfSetStartupNodes() - set source (origin) nodes */
inline void PfSetStartupNodes()
{
/* example: */
Node &n1 = *base::m_nodes.CreateNewNode();
.
. // setup node members here
.
base::m_nodes.InsertOpenNode(n1);
}
/** Example: PfFollowNode() - set following (child) nodes of the given node */
inline void PfFollowNode(Node &org)
{
for (each follower of node org) {
Node &n = *base::m_nodes.CreateNewNode();
.
. // setup node members here
.
n.m_parent = &org; // set node's parent to allow back tracking
AddNewNode(n);
}
}
/** Example: PfCalcCost() - set path cost from origin to the given node */
inline bool PfCalcCost(Node &n)
{
/* evaluate last step cost */
int cost = ...;
/* set the node cost as sum of parent's cost and last step cost */
n.m_cost = n.m_parent->m_cost + cost;
return true; // true if node is valid follower (i.e. no obstacle was found)
}
/** Example: PfCalcEstimate() - set path cost estimate from origin to the target through given node */
inline bool PfCalcEstimate(Node &n)
{
/* evaluate the distance to our destination */
int distance = ...;
/* set estimate as sum of cost from origin + distance to the target */
n.m_estimate = n.m_cost + distance;
return true; // true if node is valid (i.e. not too far away :)
}
/** Example: PfDetectDestination() - return true if the given node is our destination */
inline bool PfDetectDestination(Node &n)
{
bool bDest = (n.m_key.m_x == m_x2) && (n.m_key.m_y == m_y2);
return bDest;
}
#endif
};
#endif /* YAPF_BASE_HPP */
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