IntergridOperators.py

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import numpy as np
from .finiteelement import DGScalarElement
 
class IntergridOperators:
 
    def __init__(self, dim, coarse_order, fine_order):
        self.coarse_order = coarse_order
        self.fine_order = fine_order
        self.coarse_element = DGScalarElement(dim, coarse_order)
        self.fine_element = DGScalarElement(dim, fine_order)
 
    def prolongation(self):
        """
        Return the local prolongation matrix of size fine_element.ndof x coarse_element.ndof
        """
        coarse_ndof = self.coarse_element.ndof
        fine_ndof = self.fine_element.ndof
        Prolongation_matrix = np.zeros((fine_ndof, coarse_ndof))
        for i in range(fine_ndof):
            for j in range(coarse_ndof):
                Prolongation_matrix[i, j] = self.coarse_element.evaluate(j, self.fine_element.nodes[i])
 
        return Prolongation_matrix
    
    def restriction(self):
        """
        Return the local restriction matrix of size coarse_element.ndof x fine_element.ndof
        This is the transposed prolongation matrix
        """
        return np.transpose(self.prolongation())
    
    def injection(self):
        """
        Return the local "injection" or "interpolation" matrix of size coarse_element.ndof x fine_element.ndof
        """
        coarse_ndof = self.coarse_element.ndof
        fine_ndof = self.fine_element.ndof
        Injection_matrix = np.zeros((coarse_ndof, fine_ndof))
        for i in range(coarse_ndof):
            for j in range(fine_ndof):
                Injection_matrix[i, j] = self.fine_element.evaluate(j, self.coarse_element.nodes[i])
 
        return Injection_matrix