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SPKDTree.c
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SPKDTree.c
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#include "SPKDTree.h"
// A struct to represent a KD-Tree
struct sp_kd_tree_node_t
{
int dim;
double val;
SPKDTreeNode left, right;
SPPoint* data;
};
SPKDTreeNode SPKDTreeInit(SPPoint * arr, int size, int dims, SP_KDTREE_SPLIT_METHOD splitMethod, SP_KDTREE_MSG * msg)
{
SPKDArray kdArr;
SP_KDARRAY_MSG kdArrMsg;
SPKDTreeNode ret;
assert(msg != NULL);
if (arr == NULL || size <= 0 || dims <= 0)
{
*msg = SP_KDTREE_INVALID_ARGUMENT;
return NULL;
}
kdArr = SPKDArrayInit(arr, size, dims, &kdArrMsg); // Initialize the KD-Array
if (kdArrMsg == SP_KDARRAY_ALLOC_FAIL)
{
*msg = SP_KDTREE_ALLOC_FAIL;
return NULL;
}
// Employ recursive helper
ret = SPKDTreeInitHelp(kdArr, size, splitMethod, -1, msg);
// All done
SPKDArrayDestroy(kdArr);
return ret;
}
SPKDTreeNode SPKDTreeInitHelp(SPKDArray kdArr, int size, SP_KDTREE_SPLIT_METHOD splitMethod, int lastIndex, SP_KDTREE_MSG * msg)
{
int dim, dims, maxSpread, maxSpreadIndex, spread, i, minVal, maxVal;
SP_KDARRAY_MSG kdArrMsg;
SPKDArray* split;
SPKDTreeNode ret;
SPPoint workPoint;
assert(msg != NULL);
if (kdArr == NULL || size <= 0 || lastIndex < -1)
{
*msg = SP_KDTREE_INVALID_ARGUMENT;
return NULL;
}
// Allocate memory
ret = (SPKDTreeNode)malloc(sizeof(*ret));
if (ret == NULL)
{
*msg = SP_KDTREE_ALLOC_FAIL;
return NULL;
}
if (size == 1)
{
// Returned node will be a leaf
ret->dim = -1;
ret->val = -1.0;
ret->left = (ret->right = NULL);
ret->data = (SPPoint*)malloc(sizeof(SPPoint));
if (ret->data == NULL)
{
*msg = SP_KDTREE_ALLOC_FAIL;
free(ret);
return NULL;
}
*(ret->data) = SPKDArrayGetPointByDim(kdArr, 0, -1, &kdArrMsg); // Gets the only point in the KD-Array
}
else
{
// Returned node is not a leaf
dims = SPKDArrayGetDims(kdArr, &kdArrMsg);
// Calculate the splitting dimension
switch (splitMethod)
{
case SP_KDTREE_MAX_SPREAD:
maxSpread = 0;
maxSpreadIndex = 0;
// calculate the maximum spread dimension
for (i = 0; i < dims; i++)
{
workPoint = SPKDArrayGetPointByDim(kdArr, 0, i, &kdArrMsg);
minVal = spPointGetAxisCoor(workPoint, i);
spPointDestroy(workPoint);
workPoint = SPKDArrayGetPointByDim(kdArr, size - 1, i, &kdArrMsg);
maxVal = spPointGetAxisCoor(workPoint, i);
spPointDestroy(workPoint);
spread = maxVal - minVal;
if (spread > maxSpread)
{
maxSpread = spread;
maxSpreadIndex = i;
}
}
dim = maxSpreadIndex;
break;
case SP_KDTREE_RANDOM:
dim = rand() % dims;
break;
case SP_KDTREE_INCREMENTAL:
dim = (lastIndex + 1) % dims;
break;
}
split = SPKDArraySplit(kdArr, dim, &kdArrMsg); // Split the KD-Array according to the splitting dimension
workPoint = SPKDArrayGetPointByDim(split[0], SPKDArrayGetSize(split[0], &kdArrMsg) - 1, dim, &kdArrMsg);
ret->dim = dim;
ret->val = spPointGetAxisCoor(workPoint, dim);
// Employ recursion to calculate subtrees
ret->left = SPKDTreeInitHelp(split[0], SPKDArrayGetSize(split[0], &kdArrMsg), splitMethod, lastIndex + 1, msg);
ret->right = SPKDTreeInitHelp(split[1], SPKDArrayGetSize(split[1], &kdArrMsg), splitMethod, lastIndex + 1, msg);
ret->data = NULL;
// Get rid of unneeded memory
SPKDArrayDestroy(split[0]);
SPKDArrayDestroy(split[1]);
free(split);
spPointDestroy(workPoint);
}
// All done
*msg = SP_KDTREE_SUCCESS;
return ret;
}
int* SPKDTreeKNN(SPKDTreeNode tree, SPPoint p, int k, SP_KDTREE_MSG* msg)
{
int i;
int* res;
SPBPQueue bpq;
SPListElement head;
if(tree == NULL || k <= 0)
{
*msg = SP_KDTREE_INVALID_ARGUMENT;
return NULL;
}
bpq = spBPQueueCreate(k);
if(bpq == NULL)
{
*msg = SP_KDTREE_ALLOC_FAIL;
return NULL;
}
res = (int*) malloc(k * sizeof(int));
if(res == NULL)
{
*msg = SP_KDTREE_ALLOC_FAIL;
spBPQueueDestroy(bpq);
return NULL;
}
// Call SPKDTreeKNNRecursive to fill the bpq with the k nearest neighbors
SPKDTreeKNNRecursive(tree, p, bpq, msg);
if (*msg != SP_KDTREE_SUCCESS)
{
spBPQueueDestroy(bpq);
return NULL;
}
// Cast the bpq to an array
for(i = 0; i < k; i++)
{
head = spBPQueuePeek(bpq);
res[i] = spListElementGetIndex(head);
spListElementDestroy(head);
spBPQueueDequeue(bpq);
}
spBPQueueDestroy(bpq);
*msg = SP_KDTREE_SUCCESS;
return res;
}
void SPKDTreeKNNRecursive(SPKDTreeNode treeNode, SPPoint p, SPBPQueue bpq, SP_KDTREE_MSG* msg)
{
SPListElement listElement;
SPPoint treePoint;
bool searchedLeft;
double dist;
if(bpq == NULL || treeNode == NULL)
{
*msg = SP_KDTREE_INVALID_ARGUMENT;
return;
}
// If treeNode is a leaf
if(treeNode->left == NULL && treeNode->right == NULL)
{
treePoint = *(treeNode->data);
listElement = spListElementCreate(spPointGetIndex(treePoint), spPointL2SquaredDistance(p, treePoint));
spBPQueueEnqueue(bpq, listElement);
spListElementDestroy(listElement);
*msg = SP_KDTREE_SUCCESS;
return;
}
// Turn to search the tree that would've contain the point p (if it was in the tree)
if(spPointGetAxisCoor(p, treeNode->dim) <= treeNode->val)
{
searchedLeft = true;
SPKDTreeKNNRecursive(treeNode->left, p, bpq, msg);
if (*msg != SP_KDTREE_SUCCESS)
return;
}
else
{
searchedLeft = false;
SPKDTreeKNNRecursive(treeNode->right, p, bpq, msg);
if (*msg != SP_KDTREE_SUCCESS)
return;
}
// dist = |treeNode.val - p[treeNode.dim]|
dist = treeNode->val - spPointGetAxisCoor(p, treeNode->dim);
if(dist < 0)
dist *= -1;
//dist *= dist;
if(!spBPQueueIsFull(bpq) || dist < spBPQueueMaxValue(bpq))
{
if(searchedLeft)
SPKDTreeKNNRecursive(treeNode->right, p, bpq, msg);
else
SPKDTreeKNNRecursive(treeNode->left, p, bpq, msg);
}
}
void SPKDTreeDestroy(SPKDTreeNode tree)
{
if (tree != NULL)
{
SPKDTreeDestroy(tree->left);
SPKDTreeDestroy(tree->right);
if (tree->data != NULL)
spPointDestroy(*(tree->data));
free(tree->data);
free(tree);
}
}