Deal.ii/Description
From ScientificComputing
deal.ii — a name that originally meant to indicate that it is the successor to the Differential Equations Analysis Library — is a C++ program library targeted at the computational solution of partial differential equations using adaptive finite elements. It uses state-of-the-art programming techniques to offer you a modern interface to the complex data structures and algorithms required. The main aim of deal.II is to enable rapid development of modern finite element codes, using among other aspects adaptive meshes and a wide array of tools classes often used in finite element program.