### stencil

(pattern of input to numerical solutions at a point)

A **stencil** (in numerical analysis, i.e., methods to solve mathematical
problems through computation) is a pattern indicating the choice of data
used to calculate data at a "point". Stencils are used in solving
partial differential equations (PDEs).

In the case of PDE variables referring to space dimensions, e.g., where
something across space is changing over time, it can be thought of as the
surrounding points in space from which data is used to update the
data for a given point. For example, in a cubical grid,
it might be the points above, below, on each side, and in front of
and behind the point in question. A different stencil, for example,
would be one that includes all 26 points, that form a cube surrounding
the point in question.

The concept is also used when the "space" being handle includes
a time dimension and/or other dimensions (e.g., momentum), i.e., any
variables which the specific problem can be treat in a similar way to space.
The concept has also been adapted to non-regular grids, and for methods
using something other than points, e.g., volumes.

(*mathematics,computation*)
**Further reading:**

http://en.wikipedia.org/wiki/Stencil_(numerical_analysis)

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