Incomplete LU factorization

Incomplete LU (ILU) factorization is a method used to approximate the LU decomposition of a sparse matrix. In LU decomposition, a square matrix \( A \) is factored into the product of a lower triangular matrix \( L \) and an upper triangular matrix \( U \) such that \( A = LU \). However, in many practical applications, especially when dealing with large sparse matrices, the standard LU decomposition may not be feasible due to excessive memory requirements or computational cost.