122 lines
3.4 KiB
C++
122 lines
3.4 KiB
C++
/*
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* ***** BEGIN GPL LICENSE BLOCK *****
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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* The Original Code is Copyright (C) 2015 Blender Foundation.
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* All rights reserved.
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*
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* Contributor(s): Lukas Toenne,
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* Sergey Sharybin,
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*
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* ***** END GPL LICENSE BLOCK *****
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*/
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/** \file blender/depsgraph/intern/builder/deg_builder_transitive.cc
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* \ingroup depsgraph
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*/
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#include "intern/builder/deg_builder_transitive.h"
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extern "C" {
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#include "MEM_guardedalloc.h"
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}
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#include "intern/nodes/deg_node.h"
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#include "intern/nodes/deg_node_component.h"
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#include "intern/nodes/deg_node_operation.h"
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#include "intern/depsgraph.h"
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#include "util/deg_util_foreach.h"
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namespace DEG {
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/* -------------------------------------------------- */
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/* Performs a transitive reduction to remove redundant relations.
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* http://en.wikipedia.org/wiki/Transitive_reduction
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*
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* XXX The current implementation is somewhat naive and has O(V*E) worst case
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* runtime.
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* A more optimized algorithm can be implemented later, e.g.
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*
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* http://www.sciencedirect.com/science/article/pii/0304397588900321/pdf?md5=3391e309b708b6f9cdedcd08f84f4afc&pid=1-s2.0-0304397588900321-main.pdf
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*
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* Care has to be taken to make sure the algorithm can handle the cyclic case
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* too! (unless we can to prevent this case early on).
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*/
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enum {
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OP_VISITED = 1,
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OP_REACHABLE = 2,
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};
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static void deg_graph_tag_paths_recursive(DepsNode *node)
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{
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if (node->done & OP_VISITED) {
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return;
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}
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node->done |= OP_VISITED;
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foreach (DepsRelation *rel, node->inlinks) {
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deg_graph_tag_paths_recursive(rel->from);
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/* Do this only in inlinks loop, so the target node does not get
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* flagged.
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*/
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rel->from->done |= OP_REACHABLE;
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}
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}
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void deg_graph_transitive_reduction(Depsgraph *graph)
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{
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foreach (OperationDepsNode *target, graph->operations) {
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/* Clear tags. */
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foreach (OperationDepsNode *node, graph->operations) {
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node->done = 0;
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}
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/* mark nodes from which we can reach the target
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* start with children, so the target node and direct children are not
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* flagged.
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*/
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target->done |= OP_VISITED;
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foreach (DepsRelation *rel, target->inlinks) {
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deg_graph_tag_paths_recursive(rel->from);
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}
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/* Remove redundant paths to the target. */
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for (DepsNode::Relations::const_iterator it_rel = target->inlinks.begin();
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it_rel != target->inlinks.end();
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)
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{
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DepsRelation *rel = *it_rel;
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/* Increment in advance, so we can safely remove the relation. */
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++it_rel;
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if (rel->from->type == DEPSNODE_TYPE_TIMESOURCE) {
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/* HACK: time source nodes don't get "done" flag set/cleared. */
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/* TODO: there will be other types in future, so iterators above
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* need modifying.
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*/
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}
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else if (rel->from->done & OP_REACHABLE) {
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OBJECT_GUARDED_DELETE(rel, DepsRelation);
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}
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}
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}
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}
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} // namespace DEG
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