[yguclu]

Require all the components of a VectorFemSpace to share the same DomainDecomposition object (fixes #615).

A VectorFemSpace contains spaces defined on the same patch, hence all its components must be decomposed in the same way across the MPI processes. Until now the constructor did not check this, and it accepted components with different local subdomains, which would silently give wrong results in any operation coupling the components locally.

• In VectorFemSpace.__init__, assert that the components share the same DomainDecomposition object
• Add two serial unit tests to psydac.fem.tests.test_vector_spaces, with shared and with different (although identical) domain decompositions
• Add an MPI unit test (at least 2 processes) where the components are decomposed along different axes, hence with different local subdomains, as in the example of VectorFemSpace does not check that its components share the same domain decomposition #615

The strict check (same object) is sufficient for PSYDAC: all the vector spaces created by the library already satisfy it. This was verified by temporarily recording every violation in the constructor while running the serial test suite (about 15400 tests), the serial multipatch and FEEC tests with SymPDE 0.20 (1873 tests), and the MPI tests of psydac.api, psydac.fem, and psydac.feec on 4 processes (1026 tests): no violation was found.

Note that this tightens the API: user code which builds the components of a vector space with separate (even if identical) DomainDecomposition objects now raises an AssertionError, also in serial. The fix is to create one DomainDecomposition and pass it to all the components.

[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

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🟢 Metrics 11 complexity · 0 duplication

Metric	Results
Complexity	11
Duplication	0

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🟢 Coverage 70.83% diff coverage · -0.01% coverage variation

Metric	Results
Coverage variation	✅ -0.01% coverage variation
Diff coverage	✅ 70.83% diff coverage

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Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (d3b2c8e)	52303	33576	64.20%
Head commit (3080612)	104654 (+52351)	67170 (+33594)	64.18% (-0.01%)

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#625)	24	17	70.83%

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

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[FrederikSchnack]

Except for adding a MPI test, this looks good to me.