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Improvements of the monotonous infill ordering:

Browse source 
Calculate the initial path length and set the initial pheromone level
accordingly.
Implemented a stopping criterion to ant colony optimization.
Fixed some compilation warnings.
This commit is contained in:
bubnikv 2020-05-06 18:27:25 +02:00
parent d7b12c6e19
commit 0940db7b2e
1 changed files with 228 additions and 25 deletions
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253
src/libslic3r/Fill/FillRectilinear2.cpp
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@ -1361,7 +1361,6 @@ static void traverse_graph_generate_polylines(
continue;
}
dont_connect:
// No way to continue the current polyline. Take the rest of the line up to the outer contour.
// This will finish the polyline, starting another polyline at a new point.
going_up ? ++ it : -- it;
@ -1442,6 +1441,8 @@ struct MonotonousRegionLink
AntPath *next_flipped;
};
// Matrix of paths (AntPath) connecting ends of MontonousRegions.
// AntPath lengths and their derived visibilities refer to the length of the perimeter line if such perimeter segment exists.
class AntPathMatrix
{
public:
@ -1456,6 +1457,12 @@ public:
// From end of one region to the start of another region, both flipped or not flipped.
m_matrix(regions.size() * regions.size() * 4, AntPath{ -1., -1., initial_pheromone}) {}
void update_inital_pheromone(float initial_pheromone)
{
for (AntPath &ap : m_matrix)
ap.pheromone = initial_pheromone;
}
AntPath& operator()(const MonotonousRegion &region_from, bool flipped_from, const MonotonousRegion &region_to, bool flipped_to)
{
int row = 2 * int(&region_from - m_regions.data()) + flipped_from;
@ -1478,7 +1485,7 @@ public:
// Just apply the Eucledian distance of the end points.
path.length = unscale<float>(Vec2f(vline_to.pos - vline_from.pos, vline_to.intersections[i_to].pos() - vline_from.intersections[i_from].pos()).norm());
}
path.visibility = 1. / (path.length + EPSILON);
path.visibility = 1.f / (path.length + float(EPSILON));
}
return path;
}
@ -1497,7 +1504,7 @@ private:
const ExPolygonWithOffset &m_poly_with_offset;
const std::vector<SegmentedIntersectionLine> &m_segs;
// From end of one region to the start of another region, both flipped or not flipped.
//FIXME one may possibly use sparse representation of the matrix.
//FIXME one may possibly use sparse representation of the matrix, likely using hashing.
std::vector<AntPath> m_matrix;
};
@ -1724,7 +1731,98 @@ static std::vector<MonotonousRegion> generate_montonous_regions(std::vector<Segm
return monotonous_regions;
}
static void connect_monotonous_regions(std::vector<MonotonousRegion> &regions, std::vector<SegmentedIntersectionLine> &segs)
// Traverse path, calculate length of the draw for the purpose of optimization.
// This function is very similar to polylines_from_paths() in the way how it traverses the path, but
// polylines_from_paths() emits a path, while this function just calculates the path length.
static float montonous_region_path_length(const MonotonousRegion &region, bool dir, const ExPolygonWithOffset &poly_with_offset, const std::vector<SegmentedIntersectionLine> &segs)
{
// From the initial point (i_vline, i_intersection), follow a path.
int i_intersection = region.left_intersection_point(dir);
int i_vline = region.left.vline;
float total_length = 0.;
bool no_perimeter = false;
Vec2f last_point;
for (;;) {
const SegmentedIntersectionLine &vline = segs[i_vline];
const SegmentIntersection *it = &vline.intersections[i_intersection];
const bool going_up = it->is_low();
if (no_perimeter)
total_length += (last_point - Vec2f(vline.pos, (it + (going_up ? - 1 : 1))->pos())).norm();
int iright = it->right_horizontal();
if (going_up) {
// Traverse the complete vertical segment up to the inner contour.
for (;;) {
do {
++ it;
iright = std::max(iright, it->right_horizontal());
assert(it->is_inner());
} while (it->type != SegmentIntersection::INNER_HIGH || (it + 1)->type != SegmentIntersection::OUTER_HIGH);
int inext = it->vertical_up();
if (inext == -1 || it->vertical_up_quality() != SegmentIntersection::LinkQuality::Valid)
break;
assert(it->iContour == vline.intersections[inext].iContour);
it = vline.intersections.data() + inext;
}
} else {
// Going down.
assert(it->is_high());
assert(i_intersection > 0);
for (;;) {
do {
-- it;
if (int iright_new = it->right_horizontal(); iright_new != -1)
iright = iright_new;
assert(it->is_inner());
} while (it->type != SegmentIntersection::INNER_LOW || (it - 1)->type != SegmentIntersection::OUTER_LOW);
int inext = it->vertical_down();
if (inext == -1 || it->vertical_down_quality() != SegmentIntersection::LinkQuality::Valid)
break;
assert(it->iContour == vline.intersections[inext].iContour);
it = vline.intersections.data() + inext;
}
}
if (i_vline == region.right.vline)
break;
int inext = it->right_horizontal();
if (inext != -1 && it->next_on_contour_quality == SegmentIntersection::LinkQuality::Valid) {
// Summarize length of the connection line along the perimeter.
//FIXME should it be weighted with a lower weight than non-extruding connection line? What weight?
// Taking half of the length.
total_length += 0.5f * float(measure_perimeter_horizontal_segment_length(poly_with_offset, segs, i_vline, it - vline.intersections.data(), inext));
// Don't add distance to the next vertical line start to the total length.
no_perimeter = false;
i_intersection = inext;
} else {
// Finish the current vertical line,
going_up ? ++ it : -- it;
assert(it->is_outer());
assert(it->is_high() == going_up);
// Mark the end of this vertical line.
last_point = Vec2f(vline.pos, it->pos());
// Remember to add distance to the last point.
no_perimeter = true;
if (inext == -1) {
// Find the end of the next overlapping vertical segment.
const SegmentedIntersectionLine &vline_right = segs[i_vline + 1];
const SegmentIntersection *right = going_up ?
&vertical_run_top(vline_right, vline_right.intersections[iright]) : &vertical_run_bottom(vline_right, vline_right.intersections[iright]);
i_intersection = int(right - vline_right.intersections.data());
} else
i_intersection = inext;
}
++ i_vline;
}
return unscale<float>(total_length);
}
static void connect_monotonous_regions(std::vector<MonotonousRegion> &regions, const ExPolygonWithOffset &poly_with_offset, std::vector<SegmentedIntersectionLine> &segs)
{
// Map from low intersection to left / right side of a monotonous region.
using MapType = std::pair<SegmentIntersection*, MonotonousRegion*>;
@ -1816,6 +1914,20 @@ static void connect_monotonous_regions(std::vector<MonotonousRegion> &regions, s
}
}
#endif /* NDEBUG */
// Fill in sum length of connecting lines of a region. This length is used for optimizing the infill path for minimum length.
for (MonotonousRegion &region : regions) {
region.len1 = montonous_region_path_length(region, false, poly_with_offset, segs);
region.len2 = montonous_region_path_length(region, true, poly_with_offset, segs);
// Subtract the smaller length from the longer one, so we will optimize just with the positive difference of the two.
if (region.len1 > region.len2) {
region.len1 -= region.len2;
region.len2 = 0;
} else {
region.len2 -= region.len1;
region.len1 = 0;
}
}
}
// Raad Salman: Algorithms for the Precedence Constrained Generalized Travelling Salesperson Problem
@ -1851,6 +1963,7 @@ inline void print_ant(const std::string& fmt, TArgs&&... args) {
}
// Find a run through monotonous infill blocks using an 'Ant colony" optimization method.
// http://www.scholarpedia.org/article/Ant_colony_optimization
static std::vector<MonotonousRegionLink> chain_monotonous_regions(
std::vector<MonotonousRegion> &regions, const ExPolygonWithOffset &poly_with_offset, const std::vector<SegmentedIntersectionLine> &segs, std::mt19937_64 &rng)
{
@ -1940,14 +2053,18 @@ static std::vector<MonotonousRegionLink> chain_monotonous_regions(
};
#endif /* NDEBUG */
// How many times to repeat the ant simulation.
constexpr int num_rounds = 10;
// How many times to repeat the ant simulation (number of ant generations).
constexpr int num_rounds = 25;
// After how many rounds without an improvement to exit?
constexpr int num_rounds_no_change_exit = 8;
// With how many ants each of the run will be performed?
constexpr int num_ants = 10;
// Base (initial) pheromone level.
constexpr float pheromone_initial_deposit = 0.5f;
const int num_ants = std::min<int>(regions.size(), 10);
// Base (initial) pheromone level. This value will be adjusted based on the length of the first greedy path found.
float pheromone_initial_deposit = 0.5f;
// Evaporation rate of pheromones.
constexpr float pheromone_evaporation = 0.1f;
// Evaporation rate to diversify paths taken by individual ants.
constexpr float pheromone_diversification = 0.1f;
// Probability at which to take the next best path. Otherwise take the the path based on the cost distribution.
constexpr float probability_take_best = 0.9f;
// Exponents of the cost function.
@ -1956,6 +2073,73 @@ static std::vector<MonotonousRegionLink> chain_monotonous_regions(
AntPathMatrix path_matrix(regions, poly_with_offset, segs, pheromone_initial_deposit);
// Find an initial path in a greedy way, set the initial pheromone value to 10% of the cost of the greedy path.
{
// Construct the first path in a greedy way to calculate an initial value of the pheromone value.
queue = queue_initial;
left_neighbors_unprocessed = left_neighbors_unprocessed_initial;
assert(validate_unprocessed());
// Pick the last of the queue.
MonotonousRegionLink path_end { queue.back(), false };
queue.pop_back();
-- left_neighbors_unprocessed[path_end.region - regions.data()];
float total_length = path_end.region->length(false);
while (! queue.empty() || ! path_end.region->right_neighbors.empty()) {
// Chain.
MonotonousRegion &region = *path_end.region;
bool dir = path_end.flipped;
NextCandidate next_candidate;
next_candidate.probability = 0;
for (MonotonousRegion *next : region.right_neighbors) {
int &unprocessed = left_neighbors_unprocessed[next - regions.data()];
assert(unprocessed > 1);
if (left_neighbors_unprocessed[next - regions.data()] == 2) {
// Dependencies of the successive blocks are satisfied.
AntPath &path1 = path_matrix(region, dir, *next, false);
AntPath &path2 = path_matrix(region, dir, *next, true);
if (path1.visibility > next_candidate.probability)
next_candidate = { next, &path1, &path1, path1.visibility, false };
if (path2.visibility > next_candidate.probability)
next_candidate = { next, &path2, &path2, path2.visibility, true };
}
}
bool from_queue = next_candidate.probability == 0;
if (from_queue) {
for (MonotonousRegion *next : queue) {
AntPath &path1 = path_matrix(region, dir, *next, false);
AntPath &path2 = path_matrix(region, dir, *next, true);
if (path1.visibility > next_candidate.probability)
next_candidate = { next, &path1, &path1, path1.visibility, false };
if (path2.visibility > next_candidate.probability)
next_candidate = { next, &path2, &path2, path2.visibility, true };
}
}
// Move the other right neighbors with satisified constraints to the queue.
for (MonotonousRegion *next : region.right_neighbors)
if (-- left_neighbors_unprocessed[next - regions.data()] == 1 && next_candidate.region != next)
queue.emplace_back(next);
if (from_queue) {
// Remove the selected path from the queue.
auto it = std::find(queue.begin(), queue.end(), next_candidate.region);
assert(it != queue.end());
*it = queue.back();
queue.pop_back();
}
// Extend the path.
MonotonousRegion *next_region = next_candidate.region;
bool next_dir = next_candidate.dir;
total_length += next_region->length(next_dir) + path_matrix(*path_end.region, path_end.flipped, *next_region, next_dir).length;
path_end = { next_region, next_dir };
assert(left_neighbors_unprocessed[next_region - regions.data()] == 1);
left_neighbors_unprocessed[next_region - regions.data()] = 0;
}
// Set an initial pheromone value to 10% of the greedy path's value.
pheromone_initial_deposit = 0.1 / total_length;
path_matrix.update_inital_pheromone(pheromone_initial_deposit);
}
// Probability (unnormalized) of traversing a link between two monotonous regions.
auto path_probability = [pheromone_alpha, pheromone_beta](AntPath &path) {
return pow(path.pheromone, pheromone_alpha) * pow(path.visibility, pheromone_beta);
@ -1966,8 +2150,10 @@ static std::vector<MonotonousRegionLink> chain_monotonous_regions(
++ irun;
#endif /* SLIC3R_DEBUG_ANTS */
for (int round = 0; round < num_rounds; ++ round)
int num_rounds_no_change = 0;
for (int round = 0; round < num_rounds && num_rounds_no_change < num_rounds_no_change_exit; ++ round)
{
bool improved = false;
for (int ant = 0; ant < num_ants; ++ ant)
{
// Find a new path following the pheromones deposited by the previous ants.
@ -1977,6 +2163,8 @@ static std::vector<MonotonousRegionLink> chain_monotonous_regions(
left_neighbors_unprocessed = left_neighbors_unprocessed_initial;
assert(validate_unprocessed());
// Pick randomly the first from the queue at random orientation.
//FIXME picking the 1st monotonous region should likely be done based on accumulated pheromone level as well,
// but the inefficiency caused by the random pick of the 1st monotonous region is likely insignificant.
int first_idx = std::uniform_int_distribution<>(0, int(queue.size()) - 1)(rng);
path.emplace_back(MonotonousRegionLink{ queue[first_idx], rng() > rng.max() / 2 });
*(queue.begin() + first_idx) = std::move(queue.back());
@ -2051,7 +2239,7 @@ static std::vector<MonotonousRegionLink> chain_monotonous_regions(
for (std::vector<NextCandidate>::iterator it_next_candidate = next_candidates.begin(); it_next_candidate != next_candidates.begin() + num_direct_neighbors; ++ it_next_candidate)
if ((queue.empty() || it_next_candidate->region != queue.back()) && it_next_candidate->region != take_path->region)
queue.emplace_back(it_next_candidate->region);
if (take_path - next_candidates.begin() >= num_direct_neighbors) {
if (size_t(take_path - next_candidates.begin()) >= num_direct_neighbors) {
// Remove the selected path from the queue.
auto it = std::find(queue.begin(), queue.end(), take_path->region);
assert(it != queue.end());
@ -2083,8 +2271,10 @@ static std::vector<MonotonousRegionLink> chain_monotonous_regions(
path.back().flipped == path.back().region->flips ? path.back().region->right.high : path.back().region->right.low,
path.back().flipped == path.back().region->flips ? path.back().region->right.low : path.back().region->right.high);
// Update pheromones along this link.
take_path->link->pheromone = (1.f - pheromone_evaporation) * take_path->link->pheromone + pheromone_evaporation * pheromone_initial_deposit;
// Update pheromones along this link, see Ant Colony System (ACS) update rule.
// http://www.scholarpedia.org/article/Ant_colony_optimization
// The goal here is to lower the pheromone trace for paths taken to diversify the next path picked in the same batch of ants.
take_path->link->pheromone = (1.f - pheromone_diversification) * take_path->link->pheromone + pheromone_diversification * pheromone_initial_deposit;
assert(validate_unprocessed());
}
@ -2104,18 +2294,33 @@ static std::vector<MonotonousRegionLink> chain_monotonous_regions(
if (path_length < best_path_length) {
best_path_length = path_length;
std::swap(best_path, path);
#if 0 // #if ! defined(SLIC3R_DEBUG_ANTS) && ! defined(ndebug)
if (round == 0 && ant == 0)
std::cout << std::endl;
std::cout << Slic3r::format("round %1% ant %2% path length %3%", round, ant, path_length) << std::endl;
#endif
if (path_length == 0)
// Perfect path found.
goto end;
improved = true;
}
}
// Reinforce the path feromones with the best path.
float total_cost = best_path_length + EPSILON;
// Reinforce the path pheromones with the best path.
float total_cost = best_path_length + float(EPSILON);
for (size_t i = 0; i + 1 < path.size(); ++ i) {
MonotonousRegionLink &link = path[i];
link.next->pheromone = (1.f - pheromone_evaporation) * link.next->pheromone + pheromone_evaporation / total_cost;
}
if (improved)
num_rounds_no_change = 0;
else
++ num_rounds_no_change;
}
return best_path;
end:
return best_path;
}
// Traverse path, produce polylines.
@ -2195,7 +2400,6 @@ static void polylines_from_paths(const std::vector<MonotonousRegionLink> &path,
int inext = it->vertical_up();
if (inext == -1 || it->vertical_up_quality() != SegmentIntersection::LinkQuality::Valid)
break;
const Polygon &poly = poly_with_offset.contour(it->iContour);
assert(it->iContour == vline.intersections[inext].iContour);
emit_perimeter_segment_on_vertical_line(poly_with_offset, segs, i_vline, it->iContour, it - vline.intersections.data(), inext, *polyline, it->has_left_vertical_up());
it = vline.intersections.data() + inext;
@ -2215,7 +2419,6 @@ static void polylines_from_paths(const std::vector<MonotonousRegionLink> &path,
int inext = it->vertical_down();
if (inext == -1 || it->vertical_down_quality() != SegmentIntersection::LinkQuality::Valid)
break;
const Polygon &poly = poly_with_offset.contour(it->iContour);
assert(it->iContour == vline.intersections[inext].iContour);
emit_perimeter_segment_on_vertical_line(poly_with_offset, segs, i_vline, it->iContour, it - vline.intersections.data(), inext, *polyline, it->has_right_vertical_down());
it = vline.intersections.data() + inext;
@ -2285,8 +2488,8 @@ bool FillRectilinear2::fill_surface_by_lines(const Surface *surface, const FillP
ExPolygonWithOffset poly_with_offset(
surface->expolygon,
- rotate_vector.first,
scale_(this->overlap - (0.5 - INFILL_OVERLAP_OVER_SPACING) * this->spacing),
scale_(this->overlap - 0.5 * this->spacing));
float(scale_(this->overlap - (0.5 - INFILL_OVERLAP_OVER_SPACING) * this->spacing)),
float(scale_(this->overlap - 0.5 * this->spacing)));
if (poly_with_offset.n_contours_inner == 0) {
// Not a single infill line fits.
//FIXME maybe one shall trigger the gap fill here?
@ -2317,7 +2520,7 @@ bool FillRectilinear2::fill_surface_by_lines(const Surface *surface, const FillP
size_t n_vlines = (bounding_box.max(0) - bounding_box.min(0) + line_spacing - 1) / line_spacing;
coord_t x0 = bounding_box.min(0);
if (params.full_infill())
x0 += (line_spacing + SCALED_EPSILON) / 2;
x0 += (line_spacing + coord_t(SCALED_EPSILON)) / 2;
#ifdef SLIC3R_DEBUG
static int iRun = 0;
@ -2359,7 +2562,7 @@ bool FillRectilinear2::fill_surface_by_lines(const Surface *surface, const FillP
bool monotonous_infill = params.monotonous; // || params.density > 0.99;
if (monotonous_infill) {
std::vector<MonotonousRegion> regions = generate_montonous_regions(segs);
connect_monotonous_regions(regions, segs);
connect_monotonous_regions(regions, poly_with_offset, segs);
if (! regions.empty()) {
std::mt19937_64 rng;
std::vector<MonotonousRegionLink> path = chain_monotonous_regions(regions, poly_with_offset, segs, rng);
@ -2478,10 +2681,10 @@ Polylines FillCubic::fill_surface(const Surface *surface, const FillParams &para
params3.dont_connect = true;
Polylines polylines_out;
coordf_t dx = sqrt(0.5) * z;
if (! fill_surface_by_lines(surface, params2, 0.f, dx, polylines_out) ||
! fill_surface_by_lines(surface, params2, float(M_PI / 3.), - dx, polylines_out) ||
if (! fill_surface_by_lines(surface, params2, 0.f, float(dx), polylines_out) ||
! fill_surface_by_lines(surface, params2, float(M_PI / 3.), - float(dx), polylines_out) ||
// Rotated by PI*2/3 + PI to achieve reverse sloping wall.
! fill_surface_by_lines(surface, params3, float(M_PI * 2. / 3.), dx, polylines_out)) {
! fill_surface_by_lines(surface, params3, float(M_PI * 2. / 3.), float(dx), polylines_out)) {
printf("FillCubic::fill_surface() failed to fill a region.\n");
}
return polylines_out;