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A nodal basis interpolating at the points of a quadrature rule is collocated with it, so the mass matrix that rule assembles is diagonal. That holds exactly only if the basis and the rule carry bit-identical points, so both should read them from the same table. QGaussLobatto::points_and_weights_1D fills the one-dimensional rule keyed by its number of points n. A rule of n points is exact through degree 2n-3, so the orders 2n-4 and 2n-3 share it, which n_points_1D inverts. init_1D now reads its rule the same way. The table's values are unchanged. Co-Authored-By: Claude <noreply@anthropic.com>
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September 30, 2026 23:37
This was referenced Oct 1, 2026
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What's the advantage of this over just constructing and using a I've noticed that multiple coding agents have a tendency to rewrite rather than reuse existing APIs, and that sure feels like what's happening here. |
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You nailed it. We don't need this for the basis work 
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"That's on me" |
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Exposes the 1D Gauss-Lobatto points and weights as
QGaussLobatto::points_1D()andweights_1D(), keyed by number of points.n_points_1D()maps a rule order to that key. This lets a nodal basis collocated on the GLL points read exactly the same values as the rule, so a mass matrix assembled with that rule is exactly diagonal instead of diagonal to round-off. The basis is in #4583 (L2_LAGRANGE_GLL) and #4552 (LAGRANGE_GLL).The diff to
quadrature_gauss_lobatto_1D.Cis large, but the point and weight values are unchanged. The table is restructured soinit_1Dcopies from it, and each rule is built once on first use so that reading one needs no lock.🤖 Generated with Claude Code