mujoco

// Copyright 2023 DeepMind Technologies Limited
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef MUJOCO_SRC_ENGINE_ENGINE_ISLAND_H_
#define MUJOCO_SRC_ENGINE_ENGINE_ISLAND_H_

#include <mujoco/mjdata.h>
#include <mujoco/mjexport.h>
#include <mujoco/mjmodel.h>

#ifdef __cplusplus
extern "C" {
#endif

// disjoint-set roots are minimum tree indices; mj_dsuRoot requires parent[tree] >= 0
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
MJAPI int mj_floodFill(int* island, int nr, const int* rownnz, const int* rowadr, const int* colind,
                       int* stack);

//-------------------------- top-level API for island construction ---------------------------------

// discover islands:
//   nisland, island_dofadr, dof_island, dof_islandnext, island_efcadr, efc_island, efc_islandnext
MJAPI void mj_island(const mjModel* m, mjData* d);

#ifdef __cplusplus
}
#endif

#endif  // MUJOCO_SRC_ENGINE_ENGINE_ISLAND_H_