# HP90

A general $\text{2D-} hp\text{-adaptive}$ Finite Element (FE) implementation in Fortran 90 is described. The implementation is based on an abstract data structure, which allows to incorporate the full $hp$-adaptivity of triangular and quadrilateral finite elements. The $h$-refinement strategies are based on $h2$-refinement of quadrilaterals and $h4$-refinement of triangles. For $p$-refinement we allow the approximation order to vary within any element. The mesh refinement algorithms are restricted to 1-irregular meshes. Anisotropic and geometric refinement of quadrilateral meshes is made possible by additionally allowing double constrained nodes in rectangles. The capabilities of this $hp$-adaptive FE package are demonstrated on various test problems.

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