GetCellDOF

Get the degrees of freedom associated with a specific cell (element volume) in the finite element mesh.

Interface

MODULE SUBROUTINE GetCellDOF(obj, globalCell, ans, tsize, islocal)
  CLASS(FEDOF_), INTENT(IN) :: obj
  INTEGER(I4B), INTENT(IN) :: globalCell
  INTEGER(I4B), INTENT(INOUT) :: ans(:)
  INTEGER(I4B), INTENT(OUT) :: tsize
  LOGICAL(LGT), INTENT(IN), OPTIONAL :: islocal
END SUBROUTINE GetCellDOF

Parameters

• obj: The FEDOF_ object
• globalCell: Global cell number to retrieve DOFs for
• ans: Integer array to store the retrieved DOFs
• tsize: Output parameter containing the total size of data written in ans
• islocal: Optional logical flag - if true, globalCell is treated as a local cell number

Functionality

This method retrieves all degrees of freedom associated with a specific cell (element volume) identified by its global cell number. It performs the following operations:

1. Converts the global cell number to a local cell number if needed
2. Accesses the cell DOF information using the cell index array (cellIA)
3. Populates the ans array with the DOF indices for the specified cell
4. Sets tsize to the number of DOFs associated with the cell

The implementation leverages the cell sparsity pattern stored in the cellIA array, which provides the start and end indices for each cell's DOF information.

Implementation Details

The method first converts the global cell number to a local cell number using the mesh's GetLocalElemNumber method. It then iterates through the DOF indices stored for this cell, copying each one into the ans array and incrementing the tsize counter.

Usage

The GetCellDOF method is important for finite element implementations where you need to:

• Assemble matrices based on cell (volume) contributions
• Apply internal conditions on specific cells
• Compute cell-based integrals or other operations
• Access all degrees of freedom associated with a cell for post-processing

Unlike vertex, edge, or face DOFs which are typically shared between elements, cell DOFs are internal to a specific element, making them important for capturing high-order behavior within elements.

Example 1

import CodeBlock from '@theme/CodeBlock';

import CodeSnippet from '!!raw-loader!./_GetCellDOF_test_1.F90';

<CodeBlock language="fortran">{CodeSnippet}</CodeBlock>