P0
- centered_2nd_uniform
finite_difference
cartesian
scheme
O(dx²)
Two-point centered second-order finite difference for ∂u/∂x on a uniform Cartesian axis, expressed as a closed §4.2 arrayop lowering.
- periodic_bc
finite_difference
cartesian
boundary_condition
exact (index rewrite)
Periodic boundary handling as a downstream index-rewrite rule: wraps an out-of-range stencil access index(u, i − offset) to index(u, mod(i − offset + Nx, Nx)) on axes declared periodic by the domain.