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pathfinding.cpp
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pathfinding.cpp
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/*
* Copyright (c) 2017, 2018 Florian Jung
*
* This file is part of factorio-bot.
*
* factorio-bot is free software: you can redistribute it and/or
* modify it under the terms of the GNU General Public License,
* version 3, as published by the Free Software Foundation.
*
* factorio-bot 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 factorio-bot. If not, see <http://www.gnu.org/licenses/>.
*/
#pragma GCC optimize "-O2"
#define DEBUG_PATHFINDING
#include <vector>
#include <cmath>
#include <algorithm>
#include <unordered_set>
#ifdef DEBUG_PATHFINDING
#include "logging.hpp"
#endif
#include <boost/heap/binomial_heap.hpp>
#include <cassert>
#include "pathfinding.hpp"
#include "worldmap.hpp"
#include "factorio_io.h"
#include "pos.hpp"
#include "area.hpp"
using namespace std;
using namespace pathfinding;
/** controls the exactness-speed-tradeoff.
* if set to 1.0, this equals the textbook A*-algorithm, which
* requires that the heuristic may under- but never overestimate
* the true distance to the goal. (the direct line as used fulfils
* this).
* if set to >1, this results in a potential overestimation of the
* distance by that factor. This greatly speeds up the algorithm, at
* the cost of up results worse by up to this factor.
*/
constexpr double OVERAPPROXIMATE=1.1;
static double heuristic(const Pos& p, const Pos& goal)
{
Pos tmp = p-goal;
return sqrt(tmp.x*tmp.x+tmp.y*tmp.y)*OVERAPPROXIMATE; // FIXME overapproximation for speed
}
vector<Pos> cleanup_path(const vector<Pos>& path)
{
vector<Pos> result;
if (path.empty())
return result;
Pos dir(0,0);
for (size_t i=1; i<path.size(); i++)
{
Pos newdir = path[i-1] - path[i];
if (newdir != dir)
result.push_back(path[i-1]);
}
result.push_back(path.back());
return result;
}
vector<Pos> a_star(const Pos& start, const Area_f& end, WorldMap<walk_t>& map, double allowed_distance, double min_distance, double length_limit, double size)
{
return cleanup_path(a_star_raw(start, end, map, allowed_distance, min_distance, length_limit, size));
}
vector<Pos> a_star_raw(const Pos& start, const Area_f& end, WorldMap<walk_t>& map, double allowed_distance, double min_distance, double length_limit, double size)
{
#ifdef DEBUG_PATHFINDING
Logger log("pathfinding");
#endif
log << "a_star from " << start.str() << " to " << end.str() << " (allowed_distance=" << allowed_distance << ", min_distance=" << min_distance << ", length_limit="<<length_limit<<", size="<<size<<endl;
if (ceil(min_distance) >= allowed_distance)
throw invalid_argument("ceil(min_distance) must be smaller than allowed distance");
Area view_area = end;
view_area = view_area.expand(start);
view_area.normalize();
auto view = map.view(view_area.left_top, view_area.right_bottom, Pos(0,0));
assert(size<=1.);
vector<Pos> result;
boost::heap::binomial_heap<Entry> openlist;
vector<walk_t*> needs_cleanup;
view.at(start).openlist_handle = openlist.push(Entry(start,0.));
needs_cleanup.push_back(&view.at(start));
Logger verboselog("verbose");
int n_iterations = 0;
while (!openlist.empty())
{
verboselog << "in iteration #" << n_iterations << ": openlist has size " << openlist.size() << flush;
auto current = openlist.top();
verboselog << ", top is " << current.pos.str() << ", f=" << current.f << endl;
openlist.pop();
n_iterations++;
if (current.f >= length_limit*OVERAPPROXIMATE) // this (and any subsequent) entry is guaranteed
break; // to exceed the length_limit.
if (distance(current.pos,end) <= allowed_distance && distance(current.pos,end) >= min_distance)
{
// found goal.
Pos p = current.pos;
result.push_back(p);
while (p != start)
{
p = view.at(p).predecessor;
result.push_back(p);
}
reverse(result.begin(), result.end());
#ifdef DEBUG_PATHFINDING
for (auto pos : result) log << pos.str() << " - ";
log<<endl;
#endif
goto a_star_cleanup;
}
view.at(current.pos).in_closedlist = true;
// expand node
verboselog << "\tsuccessors: ";
Pos steps[] = {Pos(-1,-1), Pos(0, -1), Pos(1,-1),
Pos(-1, 0), Pos(1, 0),
Pos(-1, 1), Pos(0, 1), Pos(1, 1)};
for (const Pos& step : steps)
{
Pos successor = current.pos + step;
bool can_walk = false;
if (step.x == 0) // walking in vertical direction
{
auto x = current.pos.x;
auto y = min(current.pos.y, successor.y);
can_walk = view.at(x-1, y).margins[EAST] >= size/2 && view.at(x, y).margins[WEST] >= size/2 && view.at(x-1,y).can_walk && view.at(x,y).can_walk;
}
else if (step.y == 0) // walking in horizontal direction
{
auto x = min(current.pos.x, successor.x);
auto y = current.pos.y;
can_walk = view.at(x, y-1).margins[SOUTH] >= size/2 && view.at(x, y).margins[NORTH] >= size/2 && view.at(x,y-1).can_walk && view.at(x,y).can_walk;
}
else // walking diagonally
{
auto x = min(current.pos.x, successor.x);
auto y = min(current.pos.y, successor.y);
const auto& v = view.at(x,y);
can_walk = (v.margins[0]>=0.5 && v.margins[1]>=0.5 && v.margins[2]>=0.5 && v.margins[3]>=0.5) && v.can_walk && (view.at(x+step.x, y).can_walk || view.at(x, y+step.y).can_walk);
}
if (can_walk)
{
verboselog << "; " << successor.str() << flush;
auto& succ = view.at(successor);
if (succ.in_closedlist)
continue;
verboselog << "*" << flush;
double cost = sqrt(step.x*step.x + step.y*step.y);
double new_g = view.at(current.pos).g_val + cost;
if (succ.openlist_handle != openlist_handle_t() && succ.g_val < new_g) // ignore this successor, when a better way is already known
continue;
verboselog << "!" << flush;
double f = new_g + heuristic(successor, end.center());
succ.predecessor = current.pos;
succ.g_val = new_g;
verboselog << "f="<<f<<",g="<<new_g<<flush;
if (succ.openlist_handle != openlist_handle_t())
{
openlist.update(succ.openlist_handle, Entry(successor, f));
}
else
{
verboselog << "(new)" << flush;
succ.openlist_handle = openlist.push(Entry(successor, f));
needs_cleanup.push_back(&succ);
}
}
}
verboselog << endl;
}
a_star_cleanup:
for (walk_t* w : needs_cleanup)
{
w->openlist_handle = pathfinding::openlist_handle_t();
w->in_closedlist = false;
}
#ifdef DEBUG_PATHFINDING
log << "took " << n_iterations << " iterations or " << (n_iterations / max(1.0, (start-end.center()).len())) << " it/dist" << endl;
#endif
return result;
}