Validation of the a posteriori error estimator based on polynomial preserving recovery for linear elements

The purpose of this work is to investigate the quality of the a posteriori error estimator based on the polynomial preserving recovery (PPR). The main tool in this investigation is the computer-based theory. Also, a comparison is made between this estimator and the one based on the superconvergence patch recovery (SPR). The results of this comparison were found to be in favour of the estimator based on the PPR.