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Fix comprehensive memory leaks in solver setup, interpolation caching, and SubDM syncing - #178
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…uards, Stokes cleanup
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Pull request overview
This PR targets PETSc-related memory leaks and rebuild churn in the Underworld3 solver loop, especially under frequent coordinate updates and repeated solve iterations (per issue #176).
Changes:
- Added an LRU +
max_entriescap toDMInterpolationCacheto prevent unbounded cache growth when evaluation coordinates vary. - Improved PETSc object lifecycle management by explicitly destroying temporary SubDMs and cached decomposition objects (IS/SubDM), and by tearing down stale solver DM/SNES state before rebuilding.
- Switched many solver setters from full
is_setup=Falserebuilds to the narrower_needs_function_rewire=Truepath, and added a new memory leak regression test.
Reviewed changes
Copilot reviewed 6 out of 6 changed files in this pull request and generated 9 comments.
Show a summary per file
| File | Description |
|---|---|
| tests/test_0006_memory_leak.py | Adds a regression test intended to detect solver-loop memory growth across many coupled solves. |
| src/underworld3/utilities/_api_tools.py | Updates SymbolicProperty change-detection behavior for solver setup invalidation. |
| src/underworld3/systems/solvers.py | Replaces many is_setup=False invalidations with _needs_function_rewire=True; expands Stokes solve() signature. |
| src/underworld3/function/dminterpolation_cache.py | Implements an LRU eviction policy with max_entries and eviction stats. |
| src/underworld3/discretisation/discretisation_mesh_variables.py | Destroys temporary SubDM created during local→global vector sync. |
| src/underworld3/cython/petsc_generic_snes_solvers.pyx | Adds explicit cleanup for solver DM/SNES and decomposition caches; caches IS sets to avoid per-solve allocations; fixes local/global Vec restore. |
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| @@ -97,14 +97,6 @@ def __get__(self, obj, objtype=None): | |||
| def __set__(self, obj, value): | |||
| """Set the value, with automatic unwrapping.""" | |||
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| if hasattr(obj, "is_setup"): | ||
| old_value = getattr(obj, self.attr_name, None) | ||
| # Use 'is not' check first for speed | ||
| if old_value is not value: | ||
| # Check for mathematical inequality (handles SymPy expressions) | ||
| if old_value != value: |
| if len(self._cache) >= self.max_entries: | ||
| # Remove oldest (first) item | ||
| oldest_key = next(iter(self._cache)) | ||
| del self._cache[oldest_key] |
| dt = 0.001 | ||
| advdiff.solve(timestep=dt) | ||
| with swarm.access(swarm): |
| for line in f: | ||
| if line.startswith('VmRSS:'): | ||
| return int(line.split()[1]) / 1024.0 # MiB | ||
| except: |
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| def test_stokes_advdiff_memory_leak(): | ||
| comm = MPI.COMM_WORLD | ||
| rank = comm.Get_rank() | ||
| size = comm.Get_size() | ||
| # Parameters | ||
| res = 32 | ||
| n_steps = 100 | ||
| warmup_step = 30 | ||
| # Setup mesh | ||
| mesh = uw.meshing.StructuredQuadBox(elementRes=(res, res)) |
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| zero_init_guess: bool = True, | ||
| timestep: float = None, | ||
| _force_setup: bool = False, | ||
| verbose=False, | ||
| verbose: bool = False, | ||
| debug: bool = False, | ||
| debug_name: str = None, | ||
| evalf=False, | ||
| order=None, | ||
| picard: int = 0, |
| new_dt = float(value.data) if hasattr(value, 'data') else float(value) | ||
| if np.isclose(old_dt, new_dt, rtol=1e-12, atol=1e-15): | ||
| return | ||
| except: |
| new_dt = float(value.data) if hasattr(value, 'data') else float(value) | ||
| if np.isclose(old_dt, new_dt, rtol=1e-12, atol=1e-15): | ||
| return | ||
| except: |
lmoresi
approved these changes
May 10, 2026
lmoresi
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Looks good, Ben,
I added some diagnostics at the same time you figured out the fix. They should be complimentary and help find the issues quickly next time.
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bknight1
commented
May 10, 2026
MemberAuthor
Sounds good, thanks @lmoresi |
Closed
This was referenced May 11, 2026
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Resolves#176
Summary of Changes
This PR comprehensively addresses severe memory leaks identified in the solver loop, particularly during dynamic coordinate updates (e.g., swarm advection) and tight solve iterations.
DMInterpolationCachewith amax_entriescap (default: 10). This prevents unbounded memory growth when evaluation coordinates change every step.SubDMCleanup inMeshVariable: Added explicitsubdm.destroy()calls in_sync_lvec_to_gvecand otherMeshVariablesynchronization paths. Previously, temporarySubDMobjects created during data syncs were orphaned.SymbolicPropertyand solver setters to useself._needs_function_rewire = Trueinstead ofself.is_setup = Falsewhen only pointwise functions change. This avoids catastrophic, redundant teardowns and rebuilds of the PETScDMhierarchy..destroy()) of old PETSc FE objects,DMhierarchies, andSNESobjects within the_setup_discretisationand_buildpaths before allocating new ones.Verification and Test Findings
A new robust memory leak regression test (
tests/test_0006_memory_leak.py) was added. The test isolates steady-state leakage by warming up for 30 steps and measuring absolute memory growth over the subsequent 70 steps on a 32x32 mesh.developmentbranch): Memory grew by 77.83 MiB (~1.1 MiB leaked per step) over the final 70 steps, failing the test.fix/memory-leak-comprehensivebranch): Memory growth dropped to just 9.94 MiB (~0.14 MiB per step) over the same window. This remaining footprint represents high-water mark expansion rather than a leak. The test passes securely.All standard regression and parallel tests continue to pass.