graphprogram/graph.c

#include <stdint.h>
#include <stdio.h>
#include <time.h>
#include <stdlib.h>
#include "matrix.h"

void random_adjacency(const uint64_t vertex_count, uint64_t matrix[vertex_count][vertex_count]) {
    srand(time(NULL));

    for (uint64_t row_index = 0; row_index < vertex_count; row_index++) {
        for (uint64_t column_index = 0; column_index < vertex_count; column_index++) {
            if (column_index == row_index) {
                matrix[row_index][column_index] = 0;
                continue;
            }
            matrix[row_index][column_index] = rand() % 2;
        }
    }
}

void calculate_distance_matrix(const uint64_t vertex_count, const uint64_t adjacency_matrix[vertex_count][vertex_count], uint64_t distance_matrix[vertex_count][vertex_count]) {
    uint64_t power_matrix[vertex_count][vertex_count];
    uint64_t temp_power_matrix[vertex_count][vertex_count];
    copy(vertex_count, vertex_count, adjacency_matrix, power_matrix);

    for (uint64_t row_index = 0; row_index < vertex_count; row_index++) {
        for (uint64_t column_index = 0; column_index < vertex_count; column_index++) {
            if (row_index == column_index) {
                distance_matrix[row_index][column_index] = 0;
            } else if (adjacency_matrix[row_index][column_index] == 1) {
                distance_matrix[row_index][column_index] = 1;
            } else {
                distance_matrix[row_index][column_index] = UINT64_MAX;
            }
        }
    }

    for(uint64_t k = 2; k <= vertex_count; k++) {
        copy(vertex_count, vertex_count, power_matrix, temp_power_matrix);
        gemm_basic(vertex_count, vertex_count, adjacency_matrix, vertex_count, vertex_count, temp_power_matrix, power_matrix);

        for (uint64_t row_index = 0; row_index < vertex_count; row_index++) {
            for (uint64_t column_index = 0; column_index < vertex_count; column_index++) {
                if (power_matrix[row_index][column_index] != 0 && distance_matrix[row_index][column_index] == UINT64_MAX) {
                    distance_matrix[row_index][column_index] = k;
                }
            }
        }
    }
}

int get_eccentricities(const uint64_t vertex_count, const uint64_t distance_matrix[vertex_count][vertex_count], uint64_t eccentricities[vertex_count]) {
    uint64_t eccentricity;

    // set all eccentricities to infinity in case this is a disconnected graph
    for (uint64_t index = 0; index < vertex_count; index++) {
        eccentricities[index] = UINT64_MAX;
    }

    for (uint64_t row_index = 0; row_index < vertex_count; row_index++) {
        eccentricity = 0;

        for (uint64_t column_index = 0; column_index < vertex_count; column_index++) {
            if (distance_matrix[row_index][column_index] > eccentricity) {
                eccentricity = distance_matrix[row_index][column_index];
            }
        }
        // in case of a disconnected graph
        if (eccentricity == 0) {
            return 1;
        }
        eccentricities[row_index] = eccentricity;
    }

    return 0;
}

uint64_t get_radius(const uint64_t vertex_count, const uint64_t eccentricities[vertex_count]) {
    uint64_t radius = UINT64_MAX;

    for (uint64_t index = 0; index < vertex_count; index++) {
        if (eccentricities[index] < radius) {
            radius = eccentricities[index];
        }
    }

    return radius;
}

uint64_t get_diameter(const uint64_t vertex_count, const uint64_t eccentricities[vertex_count]) {
    uint64_t diamter = 0;

    for (uint64_t index = 0; index < vertex_count; index++) {
        // in case of a disconnected graph
        if (eccentricities[index] == UINT64_MAX) {
            return UINT64_MAX;
        }
        if (eccentricities[index] > diamter) {
            diamter = eccentricities[index];
        }
    }

    return diamter;
}

void get_centre(const uint64_t vertex_count, const uint64_t eccentricities[vertex_count], const uint64_t radius, uint64_t centre[vertex_count]) {
    for (uint64_t index = 0; index < vertex_count; index++) {
        centre[index] = 0;
    }

    for (uint64_t index = 0; index < vertex_count; index++) {
        if (eccentricities[index] == radius) {
            centre[index] = 1;
        }
    }
}