Module rbtree_int_mod


Uses:
    module kinds_mod, only: i_k
Types:
    public type rb_node_int_links
    public type rb_node_int
    public type rbtree_int
    public type rbtree_int_iterator
Variables:
    integer (kind=i_k), private, parameter :: int_variable = 0
    integer (kind=i_k), public, parameter :: RBTREE_NOT_FOUND = huge (int_variable)
Subroutines and functions:
    private function is_red (node)
    private function single_rotate (node, dir)
    private function double_rotate (node, dir)
    private recursive function validate (node) result (height)
    private recursive subroutine print_tree (node, level)
    private function create_node (key, value)
    private function node_equal (node1, node2)
    public subroutine rbtree_int_validate (rbtree, ierr)
    public subroutine rbtree_int_print (rbtree)
    public function rbtree_int_get (rbtree, key, found)
    public subroutine rbtree_int_insert (rbtree, key, value, ierr)
    public function rbtree_int_delete (rbtree, key, iter, found)
    public subroutine rbtree_int_clear (rbtree)
    public function rbtree_int_iterator_first (iter, rbtree)
    public function rbtree_int_iterator_last (iter, rbtree)
    public function rbtree_int_iterator_next (iter)
    public function rbtree_int_iterator_prev (iter)
    public function rbtree_int_iterator_set (iter, key)
    public function rbtree_int_iterator_key (iter)
    public function rbtree_int_iterator_value (iter)

Red-Black binary search tree combined with a doubly-linked list for fast iteration.

The compexity of the insert, delete, and get (i.e. find) routines is logarithmic. Iterator functions next and previous have constant complexity. The tree stores integer numbers.

The Red-Black tree is coded following the descripton from Julienne Walker at http://www.eternallyconfuzzled.com.

Author: Matthias Lieber


Description of Types

rb_node_int_links

public type rb_node_int_links
    type (rb_node_int), pointer :: n => NULL ()
end type rb_node_int_links
Helper to build an array of pointers to tree nodes. Only used internally.

rb_node_int

public type rb_node_int
    type (rb_node_int_links), dimension (0:1) :: link
    type (rb_node_int_links), dimension (0:1) :: list
    integer (kind=i_k) :: red = 0
    integer (kind=i_k) :: key = 0
    integer (kind=i_k) :: value = 0
end type rb_node_int
Components:
link pointers to left and right children
list pointers to previous and next node in sorted list
red color of the node, 1 if red, 0 if black
key the key of the data
value the node value
A tree node. Only used internally.

rbtree_int

public type rbtree_int
    type (rb_node_int), pointer :: root => NULL ()
    type (rb_node_int_links), dimension (0:1) :: list
    integer (kind=i_k) :: length = 0
end type rbtree_int
Components:
root pointer to root node
list pointers to first and last node in sorted list
length number of elements in the tree
The tree.

rbtree_int_iterator

public type rbtree_int_iterator
    type (rbtree_int), pointer :: rbtree
    type (rb_node_int), pointer :: cur => NULL ()
end type rbtree_int_iterator
Components:
rbtree pointer to the tree to iterate
cur pointer to the current node
A tree iterator type.

Description of Subroutines and Functions

is_red

private function is_red (node)
    type (rb_node_int), pointer :: node
    logical :: is_red
end function is_red
Check if node is red. Internal.

single_rotate

private function single_rotate (node, dir)
    type (rb_node_int), pointer :: node
    integer (kind=i_k), intent(in) :: dir
    type (rb_node_int), pointer :: single_rotate
end function single_rotate
Parameters:
node pivot node
dir direction of rotation, 0 means left, 1 means right
single_rotate return value, new root node of the subtree
Single rotation. Internal.

double_rotate

private function double_rotate (node, dir)
    type (rb_node_int), pointer :: node
    integer (kind=i_k), intent(in) :: dir
    type (rb_node_int), pointer :: double_rotate
end function double_rotate
Parameters:
node pivot node
dir direction of rotation, 0 means left, 1 means right
double_rotate return value, new root node of the subtree

validate

private recursive function validate (node) result (height)
    type (rb_node_int), pointer :: node
    integer (kind=i_k) :: height
end function validate
Check if tree is a valid red black tree. Internal.

print_tree

private recursive subroutine print_tree (node, level)
    type (rb_node_int), pointer :: node
    integer (kind=i_k), intent(in) :: level
end subroutine print_tree
Print tree. Internal.

create_node

private function create_node (key, value)
    integer (kind=i_k), intent(in) :: key
    integer (kind=i_k) :: value
    type (rb_node_int), pointer :: create_node
end function create_node
Parameters:
key the key
value pointer to the data the node should hold
create_node return value, the new node just created
Create new node. Internal.

node_equal

private function node_equal (node1, node2)
    type (rb_node_int), pointer :: node1
    type (rb_node_int), pointer :: node2
    integer (kind=i_k) :: node_equal
end function node_equal
Parameters:
node1 first node to compare
node2 second node to compare
node_equal return value, 1 if equal, 0 otherwise
Check if two node pointers are the same node. Internal.

rbtree_int_validate

public subroutine rbtree_int_validate (rbtree, ierr)
    type (rbtree_int), intent(in) :: rbtree
    integer (kind=i_k), optional, intent(out) :: ierr
end subroutine rbtree_int_validate
Parameters:
rbtree the red black tree
ierr error status
Check if tree is valid red black tree. Prints errors to stdout.

rbtree_int_print

public subroutine rbtree_int_print (rbtree)
    type (rbtree_int), intent(in) :: rbtree
end subroutine rbtree_int_print
Parameters:
rbtree the red black tree
Print the tree to stdout. Useful for debugging.

rbtree_int_get

public function rbtree_int_get (rbtree, key, found)
    type (rbtree_int), intent(in) :: rbtree
    integer (kind=i_k), intent(in) :: key
    logical, optional, intent(out) :: found
    integer (kind=i_k) :: rbtree_int_get
end function rbtree_int_get
Parameters:
rbtree the red black tree
key key of the entry to retrieve
found .true. if item found
rbtree_int_get return value, pointer to requested data or null if not found
Get a value from the tree. Top-down search without recursion.

rbtree_int_insert

public subroutine rbtree_int_insert (rbtree, key, value, ierr)
    type (rbtree_int), intent(inout) :: rbtree
    integer (kind=i_k), intent(in) :: key
    integer (kind=i_k) :: value
    integer (kind=i_k), optional, intent(out) :: ierr
end subroutine rbtree_int_insert
Parameters:
rbtree the red black tree
key key of the entry to insert
value pointer to value of the entry to insert
ierr optional error status, 0 means ok, 1 means duplicate key
Insert new entry to the tree. Top-down insertion without recursion.

rbtree_int_delete

public function rbtree_int_delete (rbtree, key, iter, found)
    type (rbtree_int), intent(inout) :: rbtree
    integer (kind=i_k), intent(in) :: key
    type (rbtree_int_iterator), optional, intent(inout) :: iter
    logical, optional, intent(out) :: found
    integer (kind=i_k) :: rbtree_int_delete
end function rbtree_int_delete
Parameters:
rbtree the red black tree
key key of the entry to delete
iter an optional iterator which will be repaired if damaged due to deletion
found .true. if item found and deleted
rbtree_int_delete return value, the value deleted from list or null if key not found
Delete entry from the tree. Top-down deletion without recursion.

If an optional iterator is given, it will be repaired when damaged due deletion. This damage may happen to any iterator of the tree, so you must do this when deleting entries within a tree iteration! This damage is due to the delete algorithm, which sometimes swap tree node contents. In this case, the iterator would point to the wrong node. CAUTION: Do not delete the current entry of the iterator! If you still do so, you must re-initialize the iterator. The following code snipped shows how to safely delete entries within an iteration:

       value = rbtree_int_iterator_first(rbiter, rbtree)
       do while ( associated(value) )
         ! get key of current
         key = rbtree_int_iterator_key(rbiter)
         ! this function returns true if we do not longer need this item
         useless = is_item_useless(value)
         ! iterate one item forward
         value = rbtree_int_iterator_next(rbiter)
         if(useless) then
           ! delete previous item and fix iterator if necessary
           deleted = rbtree_int_delete(rbtree, key, rbiter)
         end if
       end do

rbtree_int_clear

public subroutine rbtree_int_clear (rbtree)
    type (rbtree_int), intent(inout) :: rbtree
end subroutine rbtree_int_clear
Parameters:
rbtree the red black tree
Clear the whole tree.

rbtree_int_iterator_first

public function rbtree_int_iterator_first (iter, rbtree)
    type (rbtree_int_iterator), intent(inout) :: iter
    type (rbtree_int), target, intent(in) :: rbtree
    integer (kind=i_k) :: rbtree_int_iterator_first
end function rbtree_int_iterator_first
Parameters:
iter the iterator
rbtree the red black tree
rbtree_int_iterator_first return value, the first value in the tree
Initialize iterator for tree rbtree, position on the first element.

rbtree_int_iterator_last

public function rbtree_int_iterator_last (iter, rbtree)
    type (rbtree_int_iterator), intent(inout) :: iter
    type (rbtree_int), target, intent(in) :: rbtree
    integer (kind=i_k) :: rbtree_int_iterator_last
end function rbtree_int_iterator_last
Parameters:
iter the iterator
rbtree the red black tree
rbtree_int_iterator_last return value, the last value in the tree
Initialize iterator for tree rbtree, position on the last element.

rbtree_int_iterator_next

public function rbtree_int_iterator_next (iter)
    type (rbtree_int_iterator), intent(inout) :: iter
    integer (kind=i_k) :: rbtree_int_iterator_next
end function rbtree_int_iterator_next
Parameters:
iter the iterator
rbtree_int_iterator_next return value, the next value
Iterate to next item in tree.

CAUTION: This routine will intentionally cause a segmentation violation if the iterator is not valid!


rbtree_int_iterator_prev

public function rbtree_int_iterator_prev (iter)
    type (rbtree_int_iterator), intent(inout) :: iter
    integer (kind=i_k) :: rbtree_int_iterator_prev
end function rbtree_int_iterator_prev
Parameters:
iter the iterator
rbtree_int_iterator_prev return value, the previous value
Iterate to previous item in tree.

CAUTION: This routine will intentionally cause a segmentation violation if the iterator is not valid!


rbtree_int_iterator_set

public function rbtree_int_iterator_set (iter, key)
    type (rbtree_int_iterator), intent(inout) :: iter
    integer (kind=i_k), intent(in) :: key
    integer (kind=i_k) :: rbtree_int_iterator_set
end function rbtree_int_iterator_set
Parameters:
iter the iterator
key key of the entry to search
rbtree_int_iterator_set return value, value at the requested position ot null if not found
Set position of an iterator. Top-down search without recursion.

rbtree_int_iterator_key

public function rbtree_int_iterator_key (iter)
    type (rbtree_int_iterator), intent(in) :: iter
    integer (kind=i_k) :: rbtree_int_iterator_key
end function rbtree_int_iterator_key
Parameters:
iter the iterator
rbtree_int_iterator_key return value, the key of current node
Get the key of current node.

CAUTION: This routine will intionally cause a segmentation violation if the iterator is not valid!


rbtree_int_iterator_value

public function rbtree_int_iterator_value (iter)
    type (rbtree_int_iterator), intent(in) :: iter
    integer (kind=i_k) :: rbtree_int_iterator_value
end function rbtree_int_iterator_value
Parameters:
iter the iterator
rbtree_int_iterator_value return value, the value of current node or null if current node is null
Get value of current node.