关键词: 有限元, 上下逼近, 外推

Abstract: The calculation of π is a hint of scientific computation. It proposes a lot of information, including the positive or negative, large or small of the computational error, and some acceleration algorithms. Does the computation of partial differential equations have the similar content? This is what the author tried to answer in the paper.

Key words: finite elements, lower and upper approximations, extrapolations