InitiateNodeToElements

Inheritence

This method is inherited from the AbstractMesh class.

InitiateNodeToElements

The InitiateNodeToElements method establishes the node-to-element connectivity mapping in an AbstractMesh object. This mapping is essential for numerous mesh operations as it allows quick identification of all elements connected to any given node.

Purpose

This method builds a data structure that maps each node to all elements that contain it. This mapping is fundamental for:

• Element assembly processes
• Nodal averaging operations
• Implementing boundary conditions
• Calculating nodal normals and areas
• Supporting mesh manipulation algorithms
• Enabling efficient neighborhood searches

Interface

MODULE SUBROUTINE obj_InitiateNodeToElements(obj)
    CLASS(AbstractMesh_), INTENT(INOUT) :: obj
END SUBROUTINE obj_InitiateNodeToElements

• obj (INTENT(INOUT)) - The AbstractMesh_ object for which to create the node-to-element mapping

Algorithm

1. If the mapping is already initialized (obj%isNodeToElementsInitiated is true), the method returns immediately
2. Sets the initialization flag to true
3. Initializes a counter array nodewise_size to track how many elements are connected to each node
4. For each element in the mesh:
   • Gets the global element number
   • For each node in the element:
     • Gets the global node number
     • Converts to local node number
     • Expands the node's element list to include the current element
5. Finalizes each node's element list by trimming unused space

Implementation Details

• Uses a chunk-based allocation strategy to efficiently build the lists
• The chunk_size parameter (set to 32) controls how much the lists grow during allocation
• Performance timing is available when obj%showTime is enabled
• Debug information is provided when compiled with debug flags

Data Structures Modified

• obj%nodeData(localNodeNum)%ptr%globalElements - For each node, stores the list of global element numbers that include this node
• obj%isNodeToElementsInitiated - Flag indicating the node-to-element mapping has been built

Performance Considerations

• Time complexity is O(n × m) where n is the number of elements and m is the average number of nodes per element
• Memory requirement scales with the total number of node-element connections
• For large meshes, this operation can be memory-intensive
• The chunk-based allocation strategy helps reduce memory reallocation overhead

Usage Example

TYPE(Mesh_) :: mesh
! ... Initialize mesh ...

! Build node-to-element connectivity
CALL mesh%InitiateNodeToElements()

! Now we can easily find all elements connected to a node
elements = mesh%GetNodeToElements(globalNode=nodeNum)

Dependencies

This method depends on:

• NodeData_ExpandGlobalElements for growing the element lists

• NodeData_GetTotalGlobalElements for querying list sizes

• NodeData_GetPointerToGlobalElements for accessing the element lists

• This subroutine generates elements surrounding a node mapping, in other words it generates node to element.

• Element numbers returned by this routine are global element number.

• This mapping is stored inside obj%nodeData array

• For a local node number ii, obj%nodeData(ii)%globalElements(:) contains the global element numbers.

note

Always use method called getNodeToElements() to access this information. This method requires global Node number

caution

Always use the mapping between global node number and local node number to avoid segmentation fault