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Merged
merged 2 commits into from
Jul 23, 2025
Merged

Optimize Dijkstra and Prim's Algorithms Using Internal Node IDs #687

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366d1e7
added optimization to dijkstra and prim
Jul 17, 2025
10b80c0
Merge branch 'main' into node-ids
prex03 Jul 17, 2025
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82 changes: 45 additions & 37 deletions pydatastructs/graphs/_backend/cpp/AdjacencyList.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,10 @@ typedef struct {
std::vector<AdjacencyListGraphNode *> nodes;
std::unordered_map<std::string, GraphEdge*> edges;
std::unordered_map<std::string, AdjacencyListGraphNode*> node_map;
std::unordered_map<int, AdjacencyListGraphNode*> id_map;
std::unordered_map<int, std::string> id_to_name;
std::unordered_map<std::string, int> name_to_id;
int next_id;

} AdjacencyListGraph;

Expand All @@ -34,6 +38,9 @@ static void AdjacencyListGraph_dealloc(AdjacencyListGraph* self) {
self->edges.clear();

self->node_map.clear();
self->id_map.clear();
self->id_to_name.clear();
self->name_to_id.clear();

Py_TYPE(self)->tp_free(reinterpret_cast<PyObject*>(self));
}
Expand All @@ -46,38 +53,38 @@ static PyObject* AdjacencyListGraph_new(PyTypeObject* type, PyObject* args, PyOb
new (&self->nodes) std::vector<AdjacencyListGraphNode*>();
new (&self->edges) std::unordered_map<std::string, GraphEdge*>();
new (&self->node_map) std::unordered_map<std::string, AdjacencyListGraphNode*>();
new (&self->id_map) std::unordered_map<int, AdjacencyListGraphNode*>();
new (&self->id_to_name) std::unordered_map<int, std::string>();
new (&self->name_to_id) std::unordered_map<std::string, int>();

self->next_id = 0;

Py_ssize_t num_args = PyTuple_Size(args);
for (Py_ssize_t i = 0; i < num_args; ++i) {
PyObject* node_obj = PyTuple_GetItem(args, i);
if (!PyObject_IsInstance(node_obj, (PyObject*)&AdjacencyListGraphNodeType)) {
PyErr_SetString(PyExc_TypeError, "All arguments must be AdjacencyListGraphNode instances");

self->nodes.~vector();
self->edges.~unordered_map();
self->node_map.~unordered_map();
Py_TYPE(self)->tp_free(reinterpret_cast<PyObject*>(self));
return NULL;
}

AdjacencyListGraphNode* node = reinterpret_cast<AdjacencyListGraphNode*>(node_obj);

if (self->node_map.find(node->name) != self->node_map.end()) {
PyErr_Format(PyExc_ValueError, "Duplicate node with name '%s'", node->name.c_str());

self->nodes.~vector();
self->edges.~unordered_map();
self->node_map.~unordered_map();
Py_TYPE(self)->tp_free(reinterpret_cast<PyObject*>(self));
return NULL;
}

node->internal_id = self->next_id++;

Py_INCREF(node);
self->nodes.push_back(node);
self->node_map[node->name] = node;
self->id_map[node->internal_id] = node;
self->id_to_name[node->internal_id] = node->name;
self->name_to_id[node->name] = node->internal_id;
}
PyObject* impl_str = PyUnicode_FromString("adjacency_list");

PyObject* impl_str = PyUnicode_FromString("adjacency_list");
if (PyObject_SetAttrString(reinterpret_cast<PyObject*>(self), "_impl", impl_str) < 0) {
Py_DECREF(impl_str);
PyErr_SetString(PyExc_RuntimeError, "Failed to set _impl attribute");
Expand Down Expand Up @@ -112,9 +119,14 @@ static PyObject* AdjacencyListGraph_add_vertex(AdjacencyListGraph* self, PyObjec
return NULL;
}

node->internal_id = self->next_id++;

Py_INCREF(node);
self->nodes.push_back(node);
self->node_map[node->name] = node;
self->id_map[node->internal_id] = node;
self->id_to_name[node->internal_id] = node->name;
self->name_to_id[node->name] = node->internal_id;

Py_RETURN_NONE;
}
Expand All @@ -126,17 +138,15 @@ static PyObject* AdjacencyListGraph_is_adjacent(AdjacencyListGraph* self, PyObje
if (!PyArg_ParseTuple(args, "ss", &node1_name_c, &node2_name_c))
return NULL;

std::string node1_name(node1_name_c);
std::string node2_name(node2_name_c);

auto it1 = self->node_map.find(node1_name);
if (it1 == self->node_map.end()) {
auto it1 = self->name_to_id.find(node1_name_c);
if (it1 == self->name_to_id.end()) {
PyErr_SetString(PyExc_KeyError, "node1 not found");
return NULL;
}
AdjacencyListGraphNode* node1 = it1->second;
int id1 = it1->second;
AdjacencyListGraphNode* node1 = self->id_map[id1];

if (node1->adjacent.find(node2_name) != node1->adjacent.end()) {
if (node1->adjacent.find(node2_name_c) != node1->adjacent.end()) {
Py_RETURN_TRUE;
} else {
Py_RETURN_FALSE;
Expand All @@ -156,13 +166,13 @@ static PyObject* AdjacencyListGraph_neighbors(AdjacencyListGraph* self, PyObject
if (!PyArg_ParseTuple(args, "s", &node_name_c))
return NULL;

std::string node_name(node_name_c);
auto it = self->node_map.find(node_name);
if (it == self->node_map.end()) {
auto it = self->name_to_id.find(node_name_c);
if (it == self->name_to_id.end()) {
PyErr_SetString(PyExc_KeyError, "Node not found");
return NULL;
}
AdjacencyListGraphNode* node = it->second;
int id = it->second;
AdjacencyListGraphNode* node = self->id_map[id];

PyObject* neighbors_list = PyList_New(0);
if (!neighbors_list) return NULL;
Expand All @@ -180,23 +190,27 @@ static PyObject* AdjacencyListGraph_remove_vertex(AdjacencyListGraph* self, PyOb
if (!PyArg_ParseTuple(args, "s", &name_c))
return NULL;

std::string name(name_c);
auto it = self->node_map.find(name);
if (it == self->node_map.end()) {
auto it = self->name_to_id.find(name_c);
if (it == self->name_to_id.end()) {
PyErr_SetString(PyExc_KeyError, "Node not found");
return NULL;
}

AdjacencyListGraphNode* node_to_remove = it->second;
int id = it->second;
AdjacencyListGraphNode* node_to_remove = self->id_map[id];
std::string name = node_to_remove->name;

auto& nodes_vec = self->nodes;
nodes_vec.erase(std::remove(nodes_vec.begin(), nodes_vec.end(), node_to_remove), nodes_vec.end());

self->node_map.erase(it);
self->node_map.erase(name);
self->id_map.erase(id);
self->name_to_id.erase(name);
self->id_to_name.erase(id);

Py_XDECREF(node_to_remove);

for (auto& node_pair : self->node_map) {
for (auto& node_pair : self->id_map) {
AdjacencyListGraphNode* node = node_pair.second;
auto adj_it = node->adjacent.find(name);
if (adj_it != node->adjacent.end()) {
Expand All @@ -207,17 +221,11 @@ static PyObject* AdjacencyListGraph_remove_vertex(AdjacencyListGraph* self, PyOb

for (auto it = self->edges.begin(); it != self->edges.end(); ) {
const std::string& key = it->first;

bool involves_node = false;
size_t underscore = key.find('_');
if (underscore != std::string::npos) {
std::string source = key.substr(0, underscore);
std::string target = key.substr(underscore + 1);
if (source == name || target == name)
involves_node = true;
}
std::string src = key.substr(0, underscore);
std::string dst = key.substr(underscore + 1);

if (involves_node) {
if (src == name || dst == name) {
Py_XDECREF(it->second);
it = self->edges.erase(it);
} else {
Expand Down
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