Im have software requirement not to use dynamic memory, on top of that I trying to make kd-tree with k_dimensions, k=1 (like regular array), k=2 (2 dimensional), and so on.
In my kd_tree.h header, I have a representation of a tree (snippet):
/*
* Representation of a kd tree
*/
typedef struct tree_
{
struct tree *left;
struct tree *right;
//DEFAULT_NUMBER_OF_DIMENSIONS
float * info;
float distance_to_neighbor;
} tree;
In my kd_tree.c implementation, Im attempt to allocate/reference static memory pre allocated in array for new nodes (snippet):
#include "kdtree.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <float.h>
static int current_number_of_kd_tree_nodes=0;
static int current_number_of_data_points=0;
static int k_dimensions=0;
//pre-allocated tree nodes array
static tree tree_space [100];
//pre-allocated data_point array
//TODO: later make sure data_points is at least sizeof(t_memory)/sizeof(tree) * k_dimensions
static float data_points_space [1000];
/*=============================================================================
Function new_node
Description: given data create a tree
==========================================================*/
tree *
new_node (tree * root, float data[], int k_dimensions)
{
if (NULL == root)
{
//dynamic memory allocation is NOT allowed, malloc(sizeof(tree));
root = &tree_space [current_number_of_kd_tree_nodes];
//dynamic memory allocation is NOT allowed, root->info = malloc(k_dimensions * sizeof(float));
for (int i=0;i<k_dimensions;i++)
{
//TODO: later deal with fragmentation when you remove nodes
//HOW DO I set address of the data_points array to root->info pointer
//info+i represents info[i]
root->info = &data_points_space[current_number_of_data_points+i];
}
//too keep track of what range of the
current_number_of_data_points = current_number_of_data_points + k_dimensions;
//initialize array
if (!root)
{
printf ("insert_tree(),Out of Memory\n");
}
//set max dimensions
set_k_dimensions (k_dimensions);
root->left = NULL;
root->right = NULL;
for (int i = 0; i < get_k_dimensions (); i++)
{
root->info[i] = data[i];
}
current_number_of_kd_tree_nodes++;
}
return root;
}
Im getting crash now. Is this the correct way to reference address of data_points array root->info = &data_points_space[current_number_of_data_points+i];
?
Thanks
Just a quick quest. It looks like you want your 'root->info' to be used as an array of data points. In this case, set it to a pointer to the first element of the array.
I.e. replace the loop:
for (int i=0;i<k_dimensions;i++)
{
//TODO: later deal with fragmentation when you remove nodes
//HOW DO I set address of the data_points array to root->info pointer
//info+i represents info[i]
root->info = &data_points_space[current_number_of_data_points+i];
}
by a single assignement:
root->info = &data_points_space[current_number_of_data_points];