Make tree support deterministic without giving up its parallelism

This commit is contained in:
Hanif Koh
2026-09-06 02:29:27 +08:00
committed by HanifKoh
parent 886d43d37a
commit 60d1ceb580
2 changed files with 83 additions and 30 deletions

View File

@@ -2846,7 +2846,9 @@ void TreeSupport::drop_nodes()
const MinimumSpanningTree& mst = spanning_trees[group_index];
//In the first pass, merge all nodes that are close together.
std::vector<std::pair<const Point, SupportNode*>> nodes_vec(nodes_this_part.begin(), nodes_this_part.end());
tbb::parallel_for_each(nodes_vec.begin(), nodes_vec.end(), [&](const std::pair<const Point, SupportNode*>& entry) {
// Sequential: nodes merge into and invalidate each other in place, so parallel execution
// makes the merge order (and thus the result) depend on thread scheduling.
std::for_each(nodes_vec.begin(), nodes_vec.end(), [&](const std::pair<const Point, SupportNode*>& entry) {
SupportNode* p_node = entry.second;
SupportNode& node = *p_node;
if (!p_node->valid)
@@ -2934,7 +2936,32 @@ void TreeSupport::drop_nodes()
);
//In the second pass, move all middle nodes.
tbb::parallel_for_each(nodes_vec.begin(), nodes_vec.end(), [&](const std::pair<const Point, SupportNode*>& entry) {
// Still parallel: this pass only reads other nodes. Side effects (invalidation, new
// nodes, contact_nodes/unsupported_branch_leaves updates) are recorded per node and
// applied afterwards in node order. Node creation must be deferred too, since
// SupportNode's constructor writes `parent->child = this` on other nodes.
struct PendingNode {
Point position;
int distance_to_top = 0;
int support_roof_layers_below = 0;
bool to_buildplate = false;
SupportNode *parent = nullptr;
bool zero_max_move = false;
bool has_overhang = false;
ExPolygon overhang;
bool clamp_radius = false;
coordf_t parent_radius = 0;
double dist_to_outer = 0;
};
struct PassTwoResult {
bool invalidate = false;
bool unsupported_leaf = false;
std::vector<PendingNode> pending;
};
std::vector<PassTwoResult> pass2_results(nodes_vec.size());
auto pass2_body = [&](size_t node_idx) {
const std::pair<const Point, SupportNode*>& entry = nodes_vec[node_idx];
PassTwoResult& pass2_out = pass2_results[node_idx];
SupportNode* p_node = entry.second;
const SupportNode& node = *p_node;
@@ -2949,14 +2976,16 @@ void TreeSupport::drop_nodes()
ExPolygons overhangs_next = diff_clipped({ node.overhang }, get_collision(0, obj_layer_nr_next));
for(auto& overhang:overhangs_next) {
Point next_pt = overhang.contour.centroid();
SupportNode *next_node = m_ts_data->create_node(next_pt, p_node->distance_to_top + 1, obj_layer_nr_next,
p_node->support_roof_layers_below - (p_node->distance_to_top >= 0 ? 1 : 0),
to_buildplate, p_node, print_z_next, height_next);
next_node->max_move_dist = 0;
next_node->overhang = std::move(overhang);
m_ts_data->m_mutex.lock();
contact_nodes[layer_nr_next].emplace_back(next_node);
m_ts_data->m_mutex.unlock();
PendingNode pending;
pending.position = next_pt;
pending.distance_to_top = p_node->distance_to_top + 1;
pending.support_roof_layers_below = p_node->support_roof_layers_below - (p_node->distance_to_top >= 0 ? 1 : 0);
pending.to_buildplate = to_buildplate;
pending.parent = p_node;
pending.zero_max_move = true;
pending.has_overhang = true;
pending.overhang = std::move(overhang);
pass2_out.pending.emplace_back(std::move(pending));
}
return;
@@ -2973,17 +3002,17 @@ void TreeSupport::drop_nodes()
{
if (support_on_buildplate_only)
{
unsupported_branch_leaves.push_front({ layer_nr, p_node });
pass2_out.unsupported_leaf = true;
}
else {
p_node->valid = false;
pass2_out.invalidate = true;
}
return;
}
// if the link between parent and current is cut by contours, mark current as bottom contact node
if (p_node->parent && intersection_ln({p_node->position, p_node->parent->position}, layer_contours).empty()==false)
{
p_node->valid = false;
pass2_out.invalidate = true;
return;
}
}
@@ -3096,20 +3125,47 @@ void TreeSupport::drop_nodes()
}
auto next_collision = get_collision(0, obj_layer_nr_next);
const bool to_buildplate = !is_inside_ex(m_ts_data->m_layer_outlines[obj_layer_nr_next], next_layer_vertex);
SupportNode * next_node = m_ts_data->create_node(next_layer_vertex, node.distance_to_top + 1, obj_layer_nr_next,
node.support_roof_layers_below - (node.distance_to_top >= 0 ? 1 : 0),
to_buildplate, p_node, print_z_next, height_next);
// don't increase radius if next node will collide partially with the object (STUDIO-7883)
to_outside = projection_onto(next_collision, next_node->position);
to_outside = projection_onto(next_collision, next_layer_vertex);
direction_to_outer = to_outside - node.position;
double dist_to_outer = unscale_(direction_to_outer.cast<double>().norm());
next_node->radius = std::max(node.radius, std::min(next_node->radius, dist_to_outer));
get_max_move_dist(next_node);
m_ts_data->m_mutex.lock();
contact_nodes[layer_nr_next].push_back(next_node);
m_ts_data->m_mutex.unlock();
PendingNode pending;
pending.position = next_layer_vertex;
pending.distance_to_top = node.distance_to_top + 1;
pending.support_roof_layers_below = node.support_roof_layers_below - (node.distance_to_top >= 0 ? 1 : 0);
pending.to_buildplate = to_buildplate;
pending.parent = p_node;
pending.clamp_radius = true;
pending.parent_radius = node.radius;
pending.dist_to_outer = dist_to_outer;
pass2_out.pending.emplace_back(std::move(pending));
};
tbb::parallel_for(tbb::blocked_range<size_t>(0, nodes_vec.size()),
[&pass2_body](const tbb::blocked_range<size_t>& node_range) {
for (size_t node_idx = node_range.begin(); node_idx < node_range.end(); ++ node_idx)
pass2_body(node_idx);
});
// Apply the recorded side effects in node order.
for (size_t node_idx = 0; node_idx < nodes_vec.size(); ++ node_idx) {
PassTwoResult& pass2_out = pass2_results[node_idx];
for (PendingNode& pending : pass2_out.pending) {
SupportNode* next_node = m_ts_data->create_node(pending.position, pending.distance_to_top, obj_layer_nr_next,
pending.support_roof_layers_below, pending.to_buildplate, pending.parent, print_z_next, height_next);
if (pending.zero_max_move)
next_node->max_move_dist = 0;
if (pending.has_overhang)
next_node->overhang = std::move(pending.overhang);
if (pending.clamp_radius) {
next_node->radius = std::max(pending.parent_radius, std::min(next_node->radius, pending.dist_to_outer));
get_max_move_dist(next_node);
}
contact_nodes[layer_nr_next].push_back(next_node);
}
if (pass2_out.unsupported_leaf)
unsupported_branch_leaves.push_front({ layer_nr, nodes_vec[node_idx].second });
if (pass2_out.invalidate)
nodes_vec[node_idx].second->valid = false;
}
);
}
#ifdef SUPPORT_TREE_DEBUG_TO_SVG

View File

@@ -2382,13 +2382,10 @@ static void merge_influence_areas(
size_t num_buckets_initial;
{
// How many buckets per first merge iteration?
const size_t num_threads = tbb::this_task_arena::max_concurrency();
// 4 buckets per thread if possible,
const size_t num_buckets_min = (input_size + 2) / 4;
// 2 buckets per thread otherwise.
const size_t num_buckets_max = input_size / 2;
num_buckets_initial = num_buckets_min >= num_threads ? num_buckets_min : num_buckets_max;
const size_t bucket_size = num_buckets_min >= num_threads ? 4 : 2;
// Fixed at 4: merging is not associative, so sizing buckets off max_concurrency() made
// results depend on the core count of the slicing machine.
const size_t bucket_size = 4;
num_buckets_initial = (input_size + 2) / 4;
// Fill in the buckets.
SupportElementMerging *it = influence_areas.data();
// Reserve one more bucket to keep a single influence area which will not be merged in the first iteration.