api: add mul interp mode by mloubout · Pull Request #2788 · devitocodes/devito

mloubout · 2025-11-10T12:42:09Z

Add a mode for symmetric interpolation (sometime needed for better stability)
Added notebook on interp/staggered
Added lots of tests for it

codecov · 2025-12-11T19:54:51Z

Codecov Report

❌ Patch coverage is 96.73913% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.42%. Comparing base (ddb2459) to head (883d31e).

Files with missing lines	Patch %	Lines
devito/core/operator.py	61.53%	3 Missing and 2 partials ⚠️
devito/finite_differences/interpolation.py	93.10%	1 Missing and 1 partial ⚠️
devito/operator/operator.py	71.42%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2788      +/-   ##
==========================================
+ Coverage   83.35%   83.42%   +0.07%     
==========================================
  Files         248      249       +1     
  Lines       51734    51984     +250     
  Branches     4463     4479      +16     
==========================================
+ Hits        43122    43368     +246     
- Misses       7859     7860       +1     
- Partials      753      756       +3

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pytest-gpu-aomp-amdgpuX	`68.65% <58.24%> (-0.04%)`	⬇️
pytest-gpu-gcc-	`78.14% <96.73%> (+0.08%)`	⬆️
pytest-gpu-icx-	`78.07% <96.73%> (+0.10%)`	⬆️
pytest-gpu-nvc-nvidiaX	`69.20% <58.24%> (-0.04%)`	⬇️

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FabioLuporini · 2026-05-12T07:46:16Z


        # Code generation options for derivatives
        o['expand'] = oo.pop('expand', cls.EXPAND)
+        o['interp-mode'] = oo.pop('interp-mode', cls.INTERP_MODE)


nitpicking, this should stay in a separate section being something related to the numerics, rather than performance (which is the case of all other opt-options).
As in, later on, perhaps around line 103, with a suitable comment

I'm also not sure if we really want this to be an Operator opt-option, as opposed to a Function parameter for example or something else

it also won't play well with the tuner this way, unless we specialise it somehow

FabioLuporini · 2026-05-12T07:50:04Z

        return not self or all(s == 0 for s in self)

+    def __eq__(self, other):
+        # Two empty-or-all-zero Staggerings are equivalent regardless of arity


imho this could/should rather be normalized at __new__

Well not easily no, because you can't have a wide variety of things, like 2D functions in 3D and so on that you can't really normalize.

FabioLuporini · 2026-05-12T07:51:10Z

 evalf_table[Pow] = evalf_table[sympy.Pow]


+def _interp_mapper(source, target, dims):


would it be worth moving all of the interpolation-related stuff into a separate module finite_differences/interpolations.py ?

Seconded - it would make it easier to find things and limit the size of files

FabioLuporini · 2026-05-12T07:54:53Z

+    Interpolation mode used by `Mul._eval_at` when projecting a multi-factor
+    expression onto a target staggered location:
+
+    * `'direct'` (default): each factor is shifted to `func`'s location


what's func here (and below) ?

FabioLuporini · 2026-05-12T07:57:00Z

+      `func`'s, the symmetric form `I * (a * I^T * b)` is built -- all
+      factors are gathered at the highest-priority "block" location via
+      `I^T`, multiplied there, and the product is interpolated to `func`
+      via `I`. Use this for operators whose continuous form decomposes as


this sentence "Use this ..." doesn't seem to be the complement of the other sentence you used for the "direct" mode above i.e. "the mode to pick unless ..."

EdCaunt · 2026-05-12T09:03:30Z

Nitpick: might as well call it 08_staggered_interpolation for minimum ambiguity. Looks super good though. Is this a Claude job? Less typos than usual 😅

This is a side-quest PR, so yeah definitely claude tutorial :D

EdCaunt · 2026-05-12T09:48:14Z

 evalf_table[Pow] = evalf_table[sympy.Pow]


+def _interp_mapper(source, target, dims):


Seconded - it would make it easier to find things and limit the size of files

mloubout added the API api (symbolics, types, ...) label Nov 10, 2025

mloubout force-pushed the fd-eval-add branch 6 times, most recently from 80c1334 to 01d3d1a Compare November 14, 2025 12:57

mloubout force-pushed the fd-eval-add branch 8 times, most recently from 0823c5f to 7821fc1 Compare November 21, 2025 14:48

mloubout force-pushed the fd-eval-add branch 4 times, most recently from f91130f to 136f771 Compare December 1, 2025 12:08

mloubout force-pushed the fd-eval-add branch 3 times, most recently from edd10f2 to 26490d4 Compare December 4, 2025 20:24

Base automatically changed from fd-eval-add to main December 8, 2025 17:37

mloubout force-pushed the strict-mul-eval-at branch 4 times, most recently from 233c8fb to 99fd21a Compare December 11, 2025 19:36

mloubout force-pushed the strict-mul-eval-at branch from 99fd21a to 198aedc Compare January 7, 2026 03:53

mloubout force-pushed the strict-mul-eval-at branch from 198aedc to 8cc5c13 Compare May 11, 2026 23:18

mloubout force-pushed the strict-mul-eval-at branch 3 times, most recently from 2f6f0cf to 64aca73 Compare May 11, 2026 23:58

mloubout marked this pull request as ready for review May 12, 2026 00:14

mloubout force-pushed the strict-mul-eval-at branch 3 times, most recently from da47926 to be046cb Compare May 12, 2026 03:23

FabioLuporini reviewed May 12, 2026

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EdCaunt reviewed May 12, 2026

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mloubout added 5 commits May 12, 2026 10:50

api: prevent evaluated derivatives to be re-evaluted

42cb439

api: add mul interp mode

0c373b2

tweak mul mode

676b43e

tweak mul mode

e2897ff

api: fix symmetric interp mode and add lots of tests

e0d0d5d

mloubout force-pushed the strict-mul-eval-at branch 4 times, most recently from cb9b140 to 64ef414 Compare May 12, 2026 16:27

api: move symbolic config to its own options

883d31e

mloubout force-pushed the strict-mul-eval-at branch from 64ef414 to 883d31e Compare May 12, 2026 16:46

		evalf_table[Pow] = evalf_table[sympy.Pow]


		def _interp_mapper(source, target, dims):

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mloubout commented Nov 10, 2025 •

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codecov Bot commented Dec 11, 2025 •

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