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Export disjoint-set island helpers directly

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Signed-off-by: teerthsharma <teerths57@gmail.com>
This commit is contained in:
teerthsharma
2026-07-20 08:59:54 +05:30
committed by teerthsharma
parent d9c8bcbc8f
commit 8d9f230514
3 changed files with 67 additions and 86 deletions
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src/engine/engine_island.c
+13 -33
View File
@@ -84,7 +84,7 @@ static int arenaAllocIsland(const mjModel* m, mjData* d) {
//-------------------------- flood-fill and graph construction ------------------------------------
// find the canonical root of an active tree and compress its path
static inline int dsuFind(int* parent, int tree) {
int mj_dsuRoot(int* parent, int tree) {
int root = tree;
while (parent[root] != root) {
root = parent[root];
@@ -101,13 +101,13 @@ static inline int dsuFind(int* parent, int tree) {
// initialize all trees as inactive
static inline void dsuInit(int* parent, int ntree) {
void mj_dsuInit(int* parent, int ntree) {
mju_fillInt(parent, -1, ntree);
}
// activate and union two incident trees; -1 denotes a static endpoint
static inline void dsuUnion(int* parent, int tree1, int tree2) {
void mj_dsuMerge(int* parent, int tree1, int tree2) {
if (tree1 == -1 && tree2 == -1) {
mjERROR("self-incidence of the static tree"); // SHOULD NOT OCCUR
return;
@@ -121,8 +121,8 @@ static inline void dsuUnion(int* parent, int tree1, int tree2) {
if (parent[tree1] == parent[tree2]) return;
int root1 = dsuFind(parent, tree1);
int root2 = dsuFind(parent, tree2);
int root1 = mj_dsuRoot(parent, tree1);
int root2 = mj_dsuRoot(parent, tree2);
if (root1 < root2) {
parent[root2] = root1;
} else if (root2 < root1) {
@@ -132,8 +132,8 @@ static inline void dsuUnion(int* parent, int tree1, int tree2) {
// assign deterministic island ids in ascending canonical-root order
static inline int dsuAssign(int* island, int* parent, const int* tree_dofnum, int ntree,
int* nidof) {
int mj_dsuAssign(int* island, int* parent, const int* tree_dofnum, int ntree,
int* nidof) {
int nisland = 0;
*nidof = 0;
for (int tree=0; tree < ntree; tree++) {
@@ -145,7 +145,7 @@ static inline int dsuAssign(int* island, int* parent, const int* tree_dofnum, in
if (parent[tree] == tree) {
island[tree] = nisland++;
} else {
// Union always links the larger root to the smaller root. Since trees are visited in
// union always links the larger root to the smaller root. Since trees are visited in
// ascending order, this predecessor has already been compressed and assigned an island.
parent[tree] = parent[parent[tree]];
island[tree] = island[parent[tree]];
@@ -157,26 +157,6 @@ static inline int dsuAssign(int* island, int* parent, const int* tree_dofnum, in
}
// exported private wrappers for direct unit tests and benchmarks
int _mjPRIVATE_dsuFind(int* parent, int tree) {
return dsuFind(parent, tree);
}
void _mjPRIVATE_dsuInit(int* parent, int ntree) {
dsuInit(parent, ntree);
}
void _mjPRIVATE_dsuUnion(int* parent, int tree1, int tree2) {
dsuUnion(parent, tree1, tree2);
}
int _mjPRIVATE_dsuAssign(int* island, int* parent, const int* tree_dofnum, int ntree, int* nidof) {
return dsuAssign(island, parent, tree_dofnum, ntree, nidof);
}
// find disjoint subgraphs ("islands") given sparse symmetric adjacency matrix
// arguments:
// island (nr) - island index assigned to vertex, -1 if vertex has no edges
@@ -413,10 +393,10 @@ static void unionConstraintTrees(const mjModel* m, const mjData* d, int* parent,
// activate a singleton or union all trees in a multi-tree constraint
if (tree2 == -2) {
dsuUnion(parent, tree1, -1);
mj_dsuMerge(parent, tree1, -1);
} else {
while (tree2 != -2) {
dsuUnion(parent, tree1, tree2);
mj_dsuMerge(parent, tree1, tree2);
tree1 = tree2;
tree2 = treeNext(m, d, i, &iter);
}
@@ -458,7 +438,7 @@ static void unionConstraintTrees(const mjModel* m, const mjData* d, int* parent,
if (tree1 < 0) {
tree1 = tree2;
} else {
dsuUnion(parent, tree1, tree2);
mj_dsuMerge(parent, tree1, tree2);
}
}
}
@@ -483,11 +463,11 @@ void mj_island(const mjModel* m, mjData* d) {
// union direct tree incidence and assign deterministic components
int* efc_tree = mjSTACKALLOC(d, nefc, int);
int* parent = mjSTACKALLOC(d, ntree, int);
dsuInit(parent, ntree);
mj_dsuInit(parent, ntree);
unionConstraintTrees(m, d, parent, efc_tree);
int* tree_island = mjSTACKALLOC(d, ntree, int);
int nidof;
d->nisland = dsuAssign(tree_island, parent, m->tree_dofnum, ntree, &nidof);
d->nisland = mj_dsuAssign(tree_island, parent, m->tree_dofnum, ntree, &nidof);
// no islands found: quick return
if (!d->nisland) {
src/engine/engine_island.h
+6 -5
View File
@@ -23,11 +23,12 @@
extern "C" {
#endif
MJAPI int _mjPRIVATE_dsuFind(int* parent, int tree);
MJAPI void _mjPRIVATE_dsuInit(int* parent, int ntree);
MJAPI void _mjPRIVATE_dsuUnion(int* parent, int tree1, int tree2);
MJAPI int _mjPRIVATE_dsuAssign(int* island, int* parent,
const int* tree_dofnum, int ntree, int* nidof);
// disjoint-set roots are minimum tree indices; mj_dsuRoot requires parent[tree] >= 0
MJAPI void mj_dsuInit(int* parent, int ntree);
MJAPI void mj_dsuMerge(int* parent, int tree1, int tree2);
MJAPI int mj_dsuRoot(int* parent, int tree);
MJAPI int mj_dsuAssign(int* island, int* parent,
const int* tree_dofnum, int ntree, int* nidof);
// find disjoint subgraphs ("islands") given sparse symmetric adjacency matrix