.. _physics-mergerTreeWalker:

Merger Tree Walkers
===================

Class providing walkers for merger trees---iterator objects that traverse the nodes of a merger tree in a defined order. A walker maintains a current node pointer and advances it to the next node in the traversal sequence. Different implementations visit different subsets of nodes (all nodes, isolated halos only, branch-by-branch, construction-order) and are used by the evolver, outputter, and operator classes to apply operations over the correct set of nodes.

**Default implementation:** ``mergerTreeWalkerIsolatedNodes``

Methods
-------

``next`` → ``logical``
   Update the pointer to the next node to visit. Returns true if such a node exists, returns false if no such node exists (i.e. if all nodes have been visited already).

   * ``type(treeNode), intent(inout), pointer :: node``

``nodesRemain`` → ``logical``
   Returns true if more nodes remain to be walked to in the tree.

.. _physics-mergerTreeWalkerAllAndFormationNodes:

``mergerTreeWalkerAllAndFormationNodes``
----------------------------------------

Provides a merger tree walker which iterates depth-first over all nodes including formation nodes.

.. _physics-mergerTreeWalkerAllNodes:

``mergerTreeWalkerAllNodes``
----------------------------

Provides a merger tree walker which iterates depth-first over all all nodes.

**Methods**

* ``tabulate`` — Tabulate the virial density contrast as a function of mass and time.
* ``restoreTable`` — Restore a tabulated solution from file.
* ``storeTable`` — Store a tabulated solution to file.

.. _physics-mergerTreeWalkerAllNodesBranch:

``mergerTreeWalkerAllNodesBranch``
----------------------------------

Provides a merger tree walker which iterates depth-first over all all nodes in a given branch.

**Methods**

* ``descend`` — Descend through the hierarchy to the deepest node along the current branch.

.. _physics-mergerTreeWalkerIsolatedNodes:

``mergerTreeWalkerIsolatedNodes``
---------------------------------

Provides a merger tree walker which iterates depth-first over all isolated nodes.

**(Default implementation)**

**Methods**

* ``tabulate`` — Tabulate the virial density contrast as a function of mass and time.
* ``restoreTable`` — Restore a tabulated solution from file.
* ``storeTable`` — Store a tabulated solution to file.

.. _physics-mergerTreeWalkerIsolatedNodesBranch:

``mergerTreeWalkerIsolatedNodesBranch``
---------------------------------------

Provides a merger tree walker which iterates depth-first over all isolated nodes in a given branch.

**Methods**

* ``descend`` — Descend through the hierarchy to the deepest node along the current branch.

.. _physics-mergerTreeWalkerTreeConstruction:

``mergerTreeWalkerTreeConstruction``
------------------------------------

Provides a merger tree walker for trees under construction.

**Methods**

* ``setNode`` — Set the walker to the given node.