/**
* @brief Merges two sorted lists.
* @param[in] i_left Pointer to the head of left list.
* @param[in] i_right Pointer to the head of right list.
*/
Node * p_merge(Node * i_left, Node * i_right)
{
// left list is empty
if (i_left == nullptr)
{
return i_right;
}
// right list is empty
if (i_right == nullptr)
{
return i_left;
}
if (i_left->data < i_right->data)
{
// place at the top of list
i_left->next = p_merge(i_left->next, i_right);
// change previous of next pointer
i_left->next->prev = i_left;
i_left->prev = nullptr;
return i_left;
}
else
{
// place at the top of list
i_right->next = p_merge(i_left, i_right->next);
// change previous of next pointer
i_right->next->prev = i_right;
i_right->prev = nullptr;
return i_right;
}
}
static void
p_sort(uint* base, uint* l, uint* h, uint* p_)
{
if((h - l) <= MAXSZ) p_sort_(base, l, h);
else
{
uint* m = l + (h - l) / 2;
uint* m_ = p_ + (m - l);
#pragma omp task
p_sort(base, l, m, p_);
p_sort(base, m, h, m_);
#pragma omp taskwait
p_merge(base, l, m, m, h, p_);
}
}
/**
* @brief Sorts list using mergesort algorithms.
* @param[in] i_head Pointer to the head of list.
*/
Node * p_mergesort(Node * i_head)
{
// list is empty or has only one node
if (i_head == nullptr || i_head->next == nullptr)
{
return i_head;
}
// split list into two halfs
Node * half = p_split(i_head);
// recursively sort two halfs
i_head = p_mergesort(i_head);
half = p_mergesort(half);
// merge sorted lists
return p_merge(i_head, half);
}