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Introduction

Thorn SymBase contains a registry for symmetry conditions and for symmetry faces. Other thorns that implement symmetry boundary conditions register themselves with SymBase and reserve certain faces of the grid, so that no other boundary condition is applied there. Thorns that implement physical boundary conditions should query SymBase about the set of faces that have symmetry boundary conditions and should not apply the physical boundary condition there.

Figure A11.1: Multiple SymBase symmetry transformations across different registered symmetry faces.

A point $x$ is transformed to point $x'$ by transformation $A$, and then to point $x''$ by transformation $B$. Data is only actually stored for point $x''$.

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The driver has to be aware that it calls thorn SymBase's mapping routine before it actually interpolates. The whole mechanism is transparent for the user.