= Subdivision mask width
{title2=$w=j_{\max}-j_{\min}+1$}
For a stationary univariate refinement $S_{ij}=a_{i-mj}$, the <subdivision mask width> counts fine-grid positions from the first to the last active entry in a column, including any internal zeros. Consecutive columns are translates by $m$ rows, the <subdivision arity>. The number of old <control points> used by a particular new point is instead the size of its row stencil; it need not equal the mask width. A span convention counts $w-1$ fine intervals, so numerical width claims should specify the convention.
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