feat: add transplanted 1D quadrature maps, docs, tests by xywei · Pull Request #159 · inducer/modepy

xywei · 2026-02-24T02:24:25Z

Summary

This PR adds transplanted 1D quadrature support to modepy using Hale–Trefethen/Kosloff–Tal-Ezer style maps, with docs and tests.

Add new module: modepy/quadrature/transplanted.py
- map functions:
  - map_identity
  - map_sausage
  - map_kosloff_tal_ezer (kte / kosloff_tal_ezer)
  - map_strip
- dispatcher:
  - map_trefethen_transplant
- quadrature wrappers:
  - transplanted_1d_quadrature
  - transplanted_legendre_gauss_quadrature
Export wrappers at top level from modepy.__init__.
Add dedicated transplanted quadrature docs in doc/quadrature.rst with map-specific guidance and references.
Add transplanted-focused tests in modepy/test/test_quadrature.py (map consistency, strip endpoint rejection, KTE validation, sausage degree checks).

What for

These quadrature rules are good at integrating QBX coefficients:

API Notes

Canonical sausage API is now:
- map_name="sausage" with sausage_degree=<odd int>
Backward-compatible map-name alias is still accepted in dispatcher:
- map_name="sausage_d{odd}"
Public API for this feature is function/wrapper-based (no Transplanted* class API introduced).
exact_to is preserved for identity-preserving mappings (identity and sausage degree 1), and unset otherwise.

Documentation Updates

Added a dedicated transplanted section anchor in docs.
Clarified transformed-weight notation (w_i^{(s)} vs mapped weights).
Improved citation formatting (italic journal names + clickable DOI links).
Reduced duplicated reference text between module docstrings and doc/quadrature.rst.

Validation

ruff check
basedpyright
pytest modepy/test/test_quadrature.py -k transplanted
Full CI on PR (including docs and downstream jobs)

inducer · 2026-02-24T15:23:00Z

Thanks! Could you look at those linter failures? The biggest one is probably adding types.

inducer · 2026-02-24T15:23:16Z

(I can help if there's an issue.)

inducer · 2026-02-24T15:23:32Z

cc @ShawnL00

Copilot

Pull request overview

Adds transplanted 1D quadrature rules/maps (Hale–Trefethen and Kosloff–Tal-Ezer) to modepy, with accompanying docs, tests, and a QBX comparison example.

Changes:

Introduces modepy.quadrature.transplanted with transplant maps, a dispatcher, and transplanted quadrature classes.
Exports transplanted quadrature classes through package init modules (modepy.quadrature and top-level modepy).
Adds docs + tests for map dispatch/validation and includes a 2D QBX comparison example script.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
`modepy/quadrature/transplanted.py`	New transplanted-map implementations and transplanted quadrature classes.
`modepy/quadrature/__init__.py`	Re-exports transplanted quadrature classes from the quadrature package.
`modepy/__init__.py`	Exposes transplanted quadrature classes at the top-level `modepy` API.
`modepy/test/test_quadrature.py`	Adds unit tests for transplanted quadrature mapping/validation behavior.
`examples/plot-qbx-transplanted-vs-gauss.py`	New QBX comparison example for Gauss vs transplanted rules.
`doc/quadrature.rst`	Adds documentation section describing transplanted quadrature usage and references.

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Copilot · 2026-02-24T17:21:44Z

examples/plot-qbx-transplanted-vs-gauss.py

+OUT = "/tmp/qbx-transplanted-vs-gauss-2d.png"
+


The example writes output to a hard-coded /tmp/... path, which will fail on non-POSIX platforms (e.g. Windows) and can be surprising for users.

Consider using tempfile.gettempdir()/pathlib.Path, saving relative to the current working directory, or making the output path a CLI argument.

Copilot · 2026-02-24T17:21:44Z

modepy/quadrature/transplanted.py

+        mapped_nodes, jacobian = map_trefethen_transplant(
+            nodes_1d,
+            map_name=map_name,
+            strip_rho=strip_rho,
+            kte_rho=kte_rho,
+            kte_alpha=kte_alpha,
+        )
+        mapped_weights = quadrature.weights * jacobian
+
+        if force_dim_axis:
+            mapped_nodes = np.reshape(mapped_nodes, (1, mapped_nodes.shape[0]))
+
+        super().__init__(mapped_nodes, mapped_weights)
+


Transplanted1DQuadrature drops the base rule's exact_to information even when map_name="identity" (and similarly for identity-equivalent maps like sausage_d1). That makes q.exact_to raise AttributeError despite the transplanted rule being identical to the base rule in that case.

Consider preserving exact_to when the map is exactly the identity, while leaving it unset for non-identity maps where polynomial exactness in x is generally not preserved.

modepy/quadrature/transplanted.py

alexfikl

Very nifty! 😁

I took a quick look and left some nitpicks and questions.

alexfikl · 2026-02-24T18:42:24Z

doc/quadrature.rst

    :members:
    :show-inheritance:

+Transplanted quadrature in one dimension


I don't feel particularly strongly about this, but I haven't heard the term "transplanted" used very often, so it sounds a bit unintuitive to me. Maybe call this mapped or conformal mapped? Maybe just transformed? Although we already have a Transformed1DQuadrature that just does linear transformations.

For context, I'm mostly familiar with stuff like this from Kress' Numerical Analysis, e.g. Chapter 9.6 and some of the cited references, so it might just be a different tradition.

(Same for other places where the term is used, depending on what's decided.)

Thanks — good point. I kept “transplanted” in this PR to stay consistent with Hale & Trefethen. From what I can tell, its usage mostly appear in complex analysis literature.

That's fair enough. I'm fine with it if you guys are, just thought of raising the point for those of us less in the weeds of it 😁

One more proposal: modepy.quadrature.variable_transformation or just modepy.quadrature.transforms.

doc/quadrature.rst

alexfikl · 2026-02-24T18:50:29Z

examples/plot-qbx-transplanted-vs-gauss.py

@@ -0,0 +1,292 @@
+from __future__ import annotations


This example is pretty awesome, but I'm wondering if it's too big for modepy? Maybe better to just put it in pytential once this gets in?

For modepy, I would appreciate just a little example from the paper, e.g. Figure 7.1 or similar (doesn't need to be all those functions).

modepy/quadrature/transplanted.py

alexfikl · 2026-02-24T19:12:19Z

modepy/quadrature/transplanted.py

+    if map_name == "strip":
+        return map_strip(s, rho=strip_rho)


I don't imagine we'll be calling these in a hot loop, so the order probably doesn't matter, but would it make sense to put the strip first? My understanding is that it's the latest and the greatest, so likely to be the most used in practice.

modepy/quadrature/transplanted.py

alexfikl · 2026-02-24T19:17:40Z

modepy/quadrature/transplanted.py

+    )
+
+
+class Transplanted1DQuadrature(Quadrature):


Does this need to be a separate quadrature class? I would expect map_trefethen_transplant (or a small wrapper) to just take a Quadrature and return a Quadrature with custom nodes + weights?

I don't feel particularly strongly about that though, since it's mostly all the same. I guess if we have Transformed1DQuadrature, this makes sense too.

I saw that you already modified this, haha. I was hoping for a bit of discussion before moving things around 😟

modepy/quadrature/__init__.py

feat: add transplanted 1d quadrature

9e132f4

xywei added 4 commits February 24, 2026 09:58

fix: unblock CI

f9884a8

fix: less strict checking for the qbx example script

5f2d7a9

fix: add typing to transplanted.py

3efe064

fix: add typing to test_quadrature.py

0b90d2f

inducer requested a review from Copilot February 24, 2026 17:15

Copilot started reviewing on behalf of inducer February 24, 2026 17:16 View session

Copilot AI reviewed Feb 24, 2026

View reviewed changes

fix: address copilot reviews

dc4f215

alexfikl reviewed Feb 24, 2026

View reviewed changes

xywei added 5 commits February 25, 2026 09:03

fix: misc fixes in docs and interface

567e9a9

fix: test regex, simply kte

74b8d51

fix: tests

7aa08e3

fix: remove heavy example

200d437

fix: test typing

8988606

xywei changed the title ~~feat: add transplanted 1D quadrature maps, docs, tests, and QBX example~~ feat: add transplanted 1D quadrature maps, docs, tests Feb 25, 2026

		OUT = "/tmp/qbx-transplanted-vs-gauss-2d.png"

		)


		class Transplanted1DQuadrature(Quadrature):

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Summary

What for

API Notes

Documentation Updates

Validation

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inducer commented Feb 24, 2026

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xywei commented Feb 24, 2026 •

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