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Add basic Graph API.

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This is going to be useful with state resolution and dependency ordering,
both of which will be crutial components of Telodendria.
This commit is contained in:
Jordan Bancino 2023-07-16 01:12:56 +00:00
parent c4ef6d4ddc
commit e592cd8e5c
2 changed files with 522 additions and 0 deletions
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347
src/Graph.c Normal file
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/*
* Copyright (C) 2022-2023 Jordan Bancino <@jordan:bancino.net>
*
* Permission is hereby granted, free of charge, to any person
* obtaining a copy of this software and associated documentation files
* (the "Software"), to deal in the Software without restriction,
* including without limitation the rights to use, copy, modify, merge,
* publish, distribute, sublicense, and/or sell copies of the Software,
* and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
#include <Graph.h>
#include <Memory.h>
#include <string.h>
struct Graph
{
size_t n;
Edge *matrix;
};
Graph *
GraphCreate(size_t n)
{
Graph *g;
if (!n)
{
return NULL;
}
g = Malloc(sizeof(Graph));
if (!g)
{
return NULL;
}
g->n = n;
g->matrix = Malloc((n * n) * sizeof(Edge));
if (!g->matrix)
{
Free(g);
return NULL;
}
memset(g->matrix, 0, (n * n) * sizeof(Edge));
return g;
}
Graph *
GraphCreateWithEdges(size_t n, Edge * matrix)
{
Graph *g = GraphCreate(n);
if (!g)
{
return NULL;
}
memcpy(g->matrix, matrix, (n * n) * sizeof(Edge));
return g;
}
void
GraphFree(Graph * g)
{
if (!g)
{
return;
}
Free(g->matrix);
Free(g);
}
Edge
GraphEdgeGet(Graph * g, Node n1, Node n2)
{
if (n1 >= g->n || n2 >= g->n)
{
return -1;
}
return g->matrix[(g->n * n1) + n2];
}
Edge
GraphEdgeSet(Graph * g, Node n1, Node n2, Edge e)
{
int oldVal;
if (n1 >= g->n || n2 >= g->n)
{
return -1;
}
if (e < 0)
{
return -1;
}
oldVal = g->matrix[(g->n * n1) + n2];
g->matrix[(g->n * n1) + n2] = e;
return oldVal;
}
size_t
GraphCountNodes(Graph * g)
{
return g ? g->n : 0;
}
Node *
GraphBreadthFirstSearch(Graph * G, Node s, size_t * n)
{
Node *visited;
Node *queue;
Node *result;
size_t queueSize;
Node i;
if (!G || !n)
{
return NULL;
}
*n = 0;
result = Malloc(G->n * sizeof(Node));
if (!result)
{
return NULL;
}
if (s >= G->n)
{
Free(result);
return NULL;
}
visited = Malloc(G->n * sizeof(Node));
memset(visited, 0, G->n * sizeof(Node));
queue = Malloc(G->n * sizeof(Node));
queueSize = 0;
visited[s] = 1;
queueSize++;
queue[queueSize - 1] = s;
while (queueSize)
{
s = queue[queueSize - 1];
queueSize--;
result[*n] = s;
(*n)++;
for (i = 0; i < G->n; i++)
{
if (GraphEdgeGet(G, s, i) && !visited[i])
{
visited[i] = 1;
queueSize++;
queue[queueSize - 1] = i;
}
}
}
Free(visited);
Free(queue);
return result;
}
static void
GraphDepthFirstSearchRecursive(Graph * G, Node s, Node * result, size_t * n,
Node * visited)
{
size_t i;
visited[s] = 1;
result[*n] = s;
(*n)++;
for (i = 0; i < G->n; i++)
{
if (GraphEdgeGet(G, s, i) && !visited[i])
{
GraphDepthFirstSearchRecursive(G, i, result, n, visited);
}
}
}
Node *
GraphDepthFirstSearch(Graph * G, Node s, size_t * n)
{
Node *visited;
Node *result;
if (!G || !n)
{
return NULL;
}
result = Malloc(G->n * sizeof(Node));
if (!result)
{
return NULL;
}
*n = 0;
if (s >= G->n)
{
Free(result);
return NULL;
}
visited = Malloc(G->n * sizeof(Node));
memset(visited, 0, G->n * sizeof(Node));
GraphDepthFirstSearchRecursive(G, s, result, n, visited);
Free(visited);
return result;
}
static void
GraphTopologicalSortRecursive(Graph * G, Node s, Node * visited,
Node * stack, size_t * stackSize)
{
size_t i;
visited[s] = 1;
for (i = 0; i < G->n; i++)
{
if (GraphEdgeGet(G, s, i) && !visited[i])
{
GraphTopologicalSortRecursive(G, i, visited, stack, stackSize);
}
}
stack[*stackSize] = s;
(*stackSize)++;
}
Node *
GraphTopologicalSort(Graph * G, size_t * n)
{
Node *visited;
Node *stack;
Node *result;
size_t i;
size_t stackSize;
if (!G || !n)
{
return NULL;
}
*n = 0;
result = Malloc(G->n * sizeof(Node));
if (!result)
{
return NULL;
}
visited = Malloc(G->n * sizeof(Node));
memset(visited, 0, G->n * sizeof(Node));
stack = Malloc(G->n * sizeof(Node));
memset(stack, 0, G->n * sizeof(Node));
stackSize = 0;
for (i = 0; i < G->n; i++)
{
if (!visited[i])
{
GraphTopologicalSortRecursive(G, i, visited, stack, &stackSize);
}
}
Free(visited);
while (stackSize)
{
stackSize--;
result[*n] = stack[stackSize];
(*n)++;
}
Free(stack);
return result;
}
Graph *
GraphTranspose(Graph * G)
{
Graph *T = Malloc(sizeof(Graph));
size_t i, j;
T->n = G->n;
T->matrix = Malloc((G->n * G->n) * sizeof(Edge));
memset(T->matrix, 0, (T->n * T->n) * sizeof(Edge));
for (i = 0; i < G->n; i++)
{
for (j = 0; j < G->n; j++)
{
if (GraphEdgeGet(G, i, j))
{
GraphEdgeSet(T, j, i, GraphEdgeGet(G, i, j));
}
}
}
return T;
}

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src/include/Graph.h Normal file
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/*
* Copyright (C) 2022-2023 Jordan Bancino <@jordan:bancino.net>
*
* Permission is hereby granted, free of charge, to any person
* obtaining a copy of this software and associated documentation files
* (the "Software"), to deal in the Software without restriction,
* including without limitation the rights to use, copy, modify, merge,
* publish, distribute, sublicense, and/or sell copies of the Software,
* and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
#ifndef CYTOPLASM_GRAPH_H
#define CYTOPLASM_GRAPH_H
/***
* @Nm Graph
* @Nd Extremely simple graph, implemented as an adjacency matrix.
* @Dd July 15 2023
*
* .Nm
* is a basic graph data structure originally written for a computer
* science class on data structures and algorithms, in which it
* received full credit. This is an adaptation of the original
* implementation that follows the Cytoplasm style and uses Cytoplasm
* APIs when convenient.
* .P
* .Nm
* stores data in an adjacency matrix, which means the storage
* complexity is O(N^2), where N is the number of vertices (called
* Nodes in this implementation) in the graph. However, this makes the
* algorithms fast and efficient.
* .P
* Nodes are identified by index, so the first node is 0, the second
* is 1, and so on. This data structure does not support storing
* arbitrary data as nodes; rather, the intended use case is to add
* all your node data to an Array, thus giving each node an index,
* and then manipulating the graph with that index. This allows access
* to node data in O(1) time in call cases, and is the most memory
* efficient.
* .P
* .Nm
* can be used to store a variety of types of graphs, although it is
* primarily suited to directed and weighted graphs.
*/
#include <stddef.h>
/**
* The functions provided here operate on an opaque graph structure.
* This structure really just stores a matrix in a contiguous block of
* memory, as well as the number of nodes in the graph, but the
* structure is kept opaque so that it remains internally consistent.
* It also maintains the style of the Cytoplasm library.
*/
typedef struct Graph Graph;
/**
* An Edge is really just a weight, which is easily represented by an
* integer. However, it makes sense to alias this to Edge for clarity,
* both in the documentation and in the implementation.
*/
typedef int Edge;
/**
* A Node is really just a row or column in the matrix, which is easily
* represented by an unsigned integer. However, it makes sense to alias
* this to Node for clarity, both in the documentation and the
* implementation.
*/
typedef size_t Node;
/**
* Create a new graph structure with the given number of vertices.
*/
extern Graph *GraphCreate(size_t);
/**
* Create a new graph data structure with the given number of vertices
* and the given adjacency matrix. The adjacency matrix is copied
* verbatim into the graph data structure without any validation.
*/
extern Graph *GraphCreateWithEdges(size_t, Edge *);
/**
* Free all memory associated with the given graph. Since graphs are
* just a collection of numbers, they do not depend on each other in
* any way.
*/
extern void GraphFree(Graph *);
/**
* Get the weight of the edge connecting the node specified first to
* the node specified second. If this is a directed graph, it does not
* necessarily follow that there is an edge from the node specified
* second to the node specified first. It also does not follow that
* such an edge, if it exists, has the same weight.
* .P
* This function will return -1 if the graph is invalid or either node
* is out of bounds. It will return 0 if there is no such edge from the
* node specified first to the node specified second.
*/
extern Edge GraphEdgeGet(Graph *, Node, Node);
/**
* Set the weight of the edge connecting the node specified first to
* the node specified second. If this is not a directed graph, this
* function will have to be called twice, the second time reversing the
* order of the nodes. To remove the edge, specify a weight of 0.
*/
extern Edge GraphEdgeSet(Graph *, Node, Node, Edge);
/**
* Get the number of nodes in the given graph. This operation is a
* simple memory access that happens in O(1) time.
*/
extern size_t GraphCountNodes(Graph *);
/**
* Perform a breadth-first search on the given graph, starting at the
* specified node. This function returns a list of nodes in the order
* they were touched. The size of the list is stored in the unsigned
* integer pointed to by the last argument.
* .P
* If an error occurs, NULL will be returned. Otherwise, the returned
* pointer should be freed with the Memory API when it is no longer
* needed.
*/
extern Node * GraphBreadthFirstSearch(Graph *, Node, size_t *);
/**
* Perform a depth-first search on the given graph, starting at the
* specified node. This function returns a list of nodes in the order
* they were touched. The size of the list is stored in the unsigned
* integer pointed to by the last argument.
* .P
* If an error occurs, NULL will be returned. Otherwise the returned
* pointer should be freed with the Memory API when it is no longer
* needed.
*/
extern Node *GraphDepthFirstSearch(Graph *, Node, size_t *);
/**
* Perform a topological sort on the given graph. This function returns
* a list of nodes in topological ordering, though note that this is
* probably not the only topological ordering that exists for the
* graph. The size of the list is stored in the unsigned integer
* pointed to by the last argument. It should always be the number of
* nodes in the graph, but is provided for consistency and convenience.
* .P
* If an error occurs, NULL will be returned. Otherwise the returned
* pointer should be freed with the Memory API when it is no longer
* needed.
*/
extern Node *GraphTopologicalSort(Graph *, size_t *);
/**
* Transpose the given graph, returning a brand new graph that is the
* result of the transposition.
*/
extern Graph * GraphTranspose(Graph *);
#endif /* CYTOPLASM_GRAPH_H */