Adding QUADCOIL integration to DESC as an objective by lankef · Pull Request #2110 · PlasmaControl/DESC

lankef · 2026-03-03T17:14:21Z

This pull request adds two files under /objective, _quadcoil.py and _quadcoil_utils.py. These allows one to call QUADCOIL using a DESC equilibrium and filament coil set as input, and perform quasi-single-stage optimization on the equilibrium and/or the coilset. There are some additions in coils and curves for conversion from simsopt objects. (since quadcoil is written in the simsopt convention). Winding surface can be either fixed or auto-generated, but optimizing the geometry of the winding surface is not yet implemented. The unit test compares quadcoil to desc's built-in REGCOIL.

…also coming soon.

… optimizable_io.py and objective_funs.py to avoid error for static, empty tuple attributes and _objectives with self.coordinates == \'\'

…opy and pasting.

…nversion, but it's not working because quadcoilproxy does not directly store the input dictionary, and desc static dict cannot contain strings (?)

…: Colorbar layout of new layout engine not compatible with old engine, and a colorbar has been created. Engine not changed.

…for merging into main

dpanici · 2026-03-17T19:05:46Z

        "_use_jit",
    ]
    _static_attrs = [
+        "_static_attrs",  # A bug as of Oct 10 2025


specifically, for some reason one needs static_attrs included in the static_attrs or one will get JAX errors. This seems unintuitive but is empirically what we've found

Should I keep this? I don't need to do anything about this right?

_static_attrs is already included couple lines below. You probably had to add it before we added in master.

dpanici · 2026-03-17T20:24:51Z

+   notebooks/tutorials/coil_optimization_QUADCOIL.ipynb
   notebooks/tutorials/omnigenity.ipynb
   notebooks/tutorials/bootstrap_current.ipynb
   notebooks/tutorials/coil_stage_two_optimization.ipynb


Also need to add QUADCOIL stuff to the API, I think the file is https://github.com/PlasmaControl/DESC/blob/master/docs/api_objectives.rst?plain=1

add the objectives, I mean

Added!
9faf614

dpanici · 2026-03-17T20:41:46Z

+        targets for each objective terms individually besides using ``target``
+        and ``bounds`` that comes with other DESC objectives.
+        Targets of each property. 0 by default.
+    metric_weight : scalar or ndarray, default=None


1.0 not None

Should be fixed now.

dpanici · 2026-03-17T20:44:13Z

+    return Bnormal
+
+
+# Flipping the current potential of a quadcoil


what are the different coordinate directions/representations/normalizations used? it woudl be good to list these all somewhere, even if just as a comment or in this PR, of the differences in convention btwn DESC and QUADCOIL. Just so we have it clearly down somewhere. Seems phi is flipped?

dpanici · 2026-03-17T20:45:35Z

+    return phi_swapped
+
+
+def _quadcoil_phi_to_desc_phi(phi_mn_quadcoil, stellsym, mpol, ntor):


this is converting just phi_mn quadcoil to desc?

dpanici · 2026-03-17T20:47:03Z

+    return Phi_mn, modes_M, modes_N
+
+
+def _create_source(eq, source_grid, eval_grid):


this could be placed perhaps into the integrals/singularities.py or in a util file there. Also could be used again inside of the other places like BoundaryError. I think it is a reasonable util function, with perhaps some additional documentation attached to it

dpanici · 2026-03-17T20:47:37Z

+    return (source_profiles, source_transforms, interpolator)
+
+
+def _quadcoil_kwargs_to_field_kwargs(  # noqa: C901


would be nice to document what is being done here exactly?

dpanici · 2026-03-17T20:50:26Z

+            plasma_dofs = jnp.concatenate([rc, rs, zc, zs])
+        return plasma_dofs
+
+    def compute_surface_current_field(self, *all_params):


instead of compute_surface_current_field maybe something more like run_regcoil or solve_quadcoil_surface_current_field or something is better?

I renamed this to solve_quadcoil_surface_current_field, I also renamed compute_full to solve_quadcoil.

…ield to solve_quadcoil_surface_current_field

…maControl/DESC into ffu/quadcoil-qss-pre-commit

lankef

Addressed the comments

…coil_surface) and fixing the tutorial with refactorings suggested during the PR.

…maControl/DESC into ffu/quadcoil-qss-pre-commit

rahulgaur104 · 2026-04-24T10:48:56Z

qp_nescoil.winding_surface.plot() requires simsopt. Please replace with DESC surface plotter.

YigitElma

Thanks fore adding this!
I will review rest of the code later, but it would be nice if you can resolve the problem with CI tests first. It looks like CI and pip in general cannot install quadcoil, I couldn't install it locally either.

YigitElma · 2026-04-24T15:52:57Z

        "_use_jit",
    ]
    _static_attrs = [
+        "_static_attrs",  # A bug as of Oct 10 2025


_static_attrs is already included couple lines below. You probably had to add it before we added in master.

YigitElma · 2026-04-24T15:53:34Z

        if hasattr(self, "_constants") and ("quad_weights" not in self._constants):
-            grid = self._constants["transforms"]["grid"]
            if self._coordinates == "rtz":
+                grid = self._constants["transforms"]["grid"]


can you revert these changes?

YigitElma · 2026-04-24T15:55:32Z

    else:
        im = ax.contourf(xx, yy, data, **contourf_kwargs)
    cax = divider.append_axes("right", **cax_kwargs)
+    _set_tight_layout(fig)


This change is also unnecessary

YigitElma · 2026-04-24T15:59:37Z

 def _unmake_hashable(x):
    # turn tuple of ints and shape to ndarray
-    if isinstance(x, tuple) and x[0] == "ndarray":
+    if isinstance(x, tuple) and len(x) and x[0] == "ndarray":


I don't think it hurts to have it, but why did you need this change?

The default values for some QUADCOIL arguments are empty list/tuples (I had to do it because the adjoint derivative is wrapped in a vjp rule before handed to DESC and this way some flows are simpler). Without this check it breaks DESC Optimizable.

YigitElma · 2026-04-24T16:09:07Z

 qicna @ git+https://github.com/rogeriojorge/pyQIC/
 qsc <= 0.1.3
 shapely >= 1.8.2, <= 2.1.2
+quadcoil >= 0.1.0


Sorry if I am missing but is quadcoil a pip package? I coulnd't find it on PyPI and our CI cannot install it and the tests don't run because of that.

It wasn't but now it is!

YigitElma · 2026-04-24T16:25:47Z

@@ -0,0 +1,916 @@
+import warnings
+
+from jax import jit


Suggested change

from jax import jit

from desc.backend import jit

YigitElma · 2026-04-24T16:28:13Z

+            metric_name,
+            value_only,
+            verbose,
+    plasma_M_theta : int, optional, default=eq.M_grid


We usually give defaults at the end of the description

YigitElma · 2026-04-24T16:30:14Z

+    bs_chunk_size : int, optional, default=None
+        Size to split Biot-Savart computation into chunks of evaluation points.
+
+    Attributes


These don't seem necessary

YigitElma · 2026-04-24T16:33:15Z

+        # we set them here. This is necessary because we are calling quadcoil
+        # through quadcoil.io.quadcoil_for_diff, which cannot see their default
+        # values in quadcoil.quadcoil.
+        if "net_toroidal_current_amperes" in quadcoil_kwargs.keys():


You can replace all if/else statements by something = dict.pop("something", default)

YigitElma · 2026-04-24T16:37:36Z

+        if not plasma_N_phi:
+            plasma_N_phi = eq.N_grid
+        elif plasma_N_phi <= eq.N_grid:
+            warnings.warn(


Same as above

YigitElma · 2026-04-24T16:41:23Z

+        self._quadcoil_for_diff = jit(_quadcoil_for_diff)
+        self._quadcoil_values = jit(_quadcoil_values)
+        # ----- Setting and registering keyword arguments -----
+        self._static_attrs = _Objective._static_attrs + [


You can move this to line 165, right after docs. We usually define it there

YigitElma · 2026-04-24T16:42:39Z

+            "_field_fixed",
+            "_bs_chunk_size",
+            # Basics
+            "_static_attrs",


_Objective._static_attrs have the _static_attrs and most of these other keys in it. You can remove them safely

YigitElma · 2026-04-24T16:54:22Z

+from functools import partial
+
+import numpy as np
+from jax import jit


Suggested change

from jax import jit

from desc.backend import jit

YigitElma · 2026-04-24T17:08:19Z

+        """Computes the scalar value of the QUADCOIL proxy.
+
+        Computes the scalar value of the QUADCOIL proxy. A wrapper for
+        ``compute_full``.


Why do you have a wrapper here? And what is compute_full? You actually pass full_mode=False.

Co-authored-by: Yigit Gunsur Elmacioglu <102380275+YigitElma@users.noreply.github.com>

…maControl/DESC into ffu/quadcoil-qss-pre-commit

…dict popping with defaults using pop(default=**) to improve readability

YigitElma · 2026-05-04T23:18:33Z

@lankef https://github.com/PlasmaControl/DESC/actions/runs/25258105132/job/74060745121?pr=2110 this error happens if you commit a notebook from cluster or after running notebook in Jupyter Lab session (tbh it is very annoying and we have a long standing issue about this #1215, but it is actually not our problem but nbmake or jupyterlab's). You can check this related comment #1498 (comment) for fix. Basically change kernel name of the notebook metadata or just open/save (without running it) on VS code extension.

lankef and others added 30 commits April 4, 2025 12:23

initial commit to add a quadcoil-based objective. A direct interface …

e930a2e

…also coming soon.

initial commit of the QUADCOIL objective, tweaking 2 control flows in…

69a5e87

… optimizable_io.py and objective_funs.py to avoid error for static, empty tuple attributes and _objectives with self.coordinates == \'\'

still debugging instability

74892d8

Improving printing

395d8f9

Initial commit about single-stage

6426650

fixing init

925e19e

Updating QuadcoilObject

773651e

Completing QUADCOIL single-stage interface, testing

c36d534

Renaming and minor bug fixes

dc6a65e

Fixes for static attrs

45e88d8

Fixes for static attrs

f243182

Merge remote-tracking branch 'origin/master' into ffu/quadcoil

59ec216

Merge remote-tracking branch 'origin/master' into ffu/quadcoil

a7c368f

Merge remote-tracking branch 'origin/master' into ffu/quadcoil

87c86e4

Testing for static argument error

7e6d350

Fixing quadcoil

6507199

Adding simsopt curve conversion

c4300f5

Accommodating external fields in QuadcoilProxy

c4754d4

Minor changes

25e96af

QuadcoilField first working. Adding external coil support.

3afd240

Fixing single stage. Re-organizing quadcoil-related codes to reduce c…

e47c443

…opy and pasting.

minor fix, registering quadcoilfield.

8d8de33

Fixing data_index for quadcoilfield

b96e3db

Adding conversion from QuadcoilProxy to QuadcoilField for cutting

18e82c0

Minor update. Attempting to write a quadcoil proxy-> quadcoilfield co…

a5455f8

…nversion, but it's not working because quadcoilproxy does not directly store the input dictionary, and desc static dict cannot contain strings (?)

Minor correction, fixing coil conversion to follow simsopt updates

1d0ff07

Merge remote-tracking branch 'origin/master' into ffu/quadcoil

0ecd9f1

Moving _set_tight_layout from line 988 to 973 to avoid RuntimeError…

b6fea15

…: Colorbar layout of new layout engine not compatible with old engine, and a colorbar has been created. Engine not changed.

removing quadcoil single-stage files that are immature and not ready …

8fa750d

…for merging into main

removing quadcoil single-stage files that are immature and not ready …

7b576d1

…for merging into main

Fixing docstring

61c5c12

dpanici reviewed Mar 17, 2026

View reviewed changes

lankef and others added 4 commits March 25, 2026 14:56

Add QuadcoilProxy objective to API documentation

9faf614

Update docstring default values for metric parameters in _quadcoil.py

fcd9cc1

Renaming compute_full to solve_quadcoil and compute_surface_current_f…

cf3ad2b

…ield to solve_quadcoil_surface_current_field

Merge branch 'ffu/quadcoil-qss-pre-commit' of https://github.com/Plas…

13d3ad2

…maControl/DESC into ffu/quadcoil-qss-pre-commit

lankef commented Mar 25, 2026

View reviewed changes

dpanici requested review from dpanici and f0uriest March 26, 2026 17:45

YigitElma and others added 4 commits April 2, 2026 13:28

Merge branch 'master' into ffu/quadcoil-qss-pre-commit

2ea1032

Merge branch 'master' into ffu/quadcoil-qss-pre-commit

7dfc348

a minor renaming (solve_quadcoil_surface_current_field --> solve_quad…

4090f6a

…coil_surface) and fixing the tutorial with refactorings suggested during the PR.

Merge branch 'ffu/quadcoil-qss-pre-commit' of https://github.com/Plas…

73a1afe

…maControl/DESC into ffu/quadcoil-qss-pre-commit

Notebook update to switch from simsopt plotting to desc plotting.

eaff201

YigitElma reviewed Apr 24, 2026

View reviewed changes

lankef and others added 5 commits May 2, 2026 13:22

Update desc/geometry/curve.py

90c862c

Co-authored-by: Yigit Gunsur Elmacioglu <102380275+YigitElma@users.noreply.github.com>

formatting docstring

9871de1

Merge branch 'ffu/quadcoil-qss-pre-commit' of https://github.com/Plas…

887dfc0

…maControl/DESC into ffu/quadcoil-qss-pre-commit

formatting warnings with f-string to improve readability. Formatting …

4942d9d

…dict popping with defaults using pop(default=**) to improve readability

moving static_attrs definitions to right after the docstring.

d947a56

		return Bnormal


		# Flipping the current potential of a quadcoil

		return phi_swapped


		def _quadcoil_phi_to_desc_phi(phi_mn_quadcoil, stellsym, mpol, ntor):

		return Phi_mn, modes_M, modes_N


		def _create_source(eq, source_grid, eval_grid):

		return (source_profiles, source_transforms, interpolator)


		def _quadcoil_kwargs_to_field_kwargs( # noqa: C901

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lankef commented Mar 3, 2026

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rahulgaur104 commented Apr 24, 2026

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YigitElma commented May 4, 2026

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