Over-approximations return new object by jrobbins11 · Pull Request #57 · psu-PAC-Lab/ZonoOpt

Josh Robbins (jrobbins11) · 2026-04-12T23:45:47Z

Changing all over-approximation methods to return a new object rather than modify the object in-place
Adding unit tests to verify over-approximation methods working as expected

Copilot

Pull request overview

This PR changes the over-approximation API to return new set objects (instead of mutating in-place) and adds test fixtures + unit tests to validate over-approximation behavior across Zono/ConZono/HybZono in both the Python and C++ test suites.

Changes:

Update ConZono::constraint_reduction() (C++ and Python bindings/stubs/docs) to return a new object.
Add new overapproximation test data and new C++/Python unit tests exercising reduce_order, constraint_reduction, to_zono_approx, and convex_relaxation.
Regenerate/update published docs to reflect new return types.

Reviewed changes

Copilot reviewed 30 out of 33 changed files in this pull request and generated 9 comments.

Show a summary per file

File	Description
test/test-data/overapproximation/rand_zono.json	Adds randomized zonotope fixture for overapprox tests.
test/test-data/overapproximation/rand_hybzono.json	Adds randomized hybrid zonotope fixture for overapprox tests.
test/test-data/overapproximation/rand_conzono.json	Adds randomized constrained zonotope fixture for overapprox tests.
test/python-tests/unit_tests.py	Adds Python unit test coverage for over-approximation methods.
test/cpp-tests/src/test_overapproximation.cpp	Adds a new C++ unit test binary for over-approximation methods.
test/CMakeLists.txt	Registers the new C++ overapproximation test target.
src/ConZono.cpp	Changes `ConZono::constraint_reduction()` to return a new object and be `const`.
python/zonoopt/_core.pyi	Updates Python typing stub for `constraint_reduction()` return type/documentation.
python/src/zonoopt_py.cpp	Exposes updated `constraint_reduction()` return semantics in the Python module docs/binding.
include/zonoopt/Zono.hpp	Adds an override for `constraint_reduction()` in `Zono`.
include/zonoopt/EmptySet.hpp	Updates `constraint_reduction()` override to return a new object.
include/zonoopt/ConZono.hpp	Updates `constraint_reduction()` signature to return `unique_ptr` and be `const`.
docs/python/build/html/zonoopt.html	Regenerated Python docs to reflect new return type and docs.
docs/C++/html/Zono_8hpp_source.html	Regenerated C++ docs (Zono header source view).
docs/C++/html/search/functions_2.js	Regenerated C++ docs search index for function signatures.
docs/C++/html/search/all_2.js	Regenerated C++ docs search index for symbol changes.
docs/C++/html/index.html	Regenerated C++ docs landing page references/line numbers.
docs/C++/html/functions_func_c.html	Regenerated C++ docs function index for “c”.
docs/C++/html/functions_c.html	Regenerated C++ docs member function index for “c”.
docs/C++/html/EmptySet_8hpp_source.html	Regenerated C++ docs (EmptySet header source view).
docs/C++/html/ConZono_8hpp_source.html	Regenerated C++ docs (ConZono header source view).
docs/C++/html/classZonoOpt_1_1Zono.html	Regenerated C++ docs (Zono class page).
docs/C++/html/classZonoOpt_1_1Zono-members.html	Regenerated C++ docs (Zono members page).
docs/C++/html/classZonoOpt_1_1Point.html	Regenerated C++ docs (Point class page).
docs/C++/html/classZonoOpt_1_1Point-members.html	Regenerated C++ docs (Point members page).
docs/C++/html/classZonoOpt_1_1EmptySet.html	Regenerated C++ docs (EmptySet class page).
docs/C++/html/classZonoOpt_1_1EmptySet-members.html	Regenerated C++ docs (EmptySet members page).
docs/C++/html/classZonoOpt_1_1ConZono.html	Regenerated C++ docs (ConZono class page).
docs/C++/html/classZonoOpt_1_1ConZono-members.html	Regenerated C++ docs (ConZono members page).

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Copilot · 2026-04-12T23:51:06Z

        // make sure conzono isn't empty (interval check)
-        for (int j = 0; j < this->nG; ++j)
+        for (int j = 0; j < Z->nG; ++j)
        {
            if (E.get_element(j).is_empty())
-                throw std::runtime_error("ConZono constraint reduction: set is empty");
+                return std::make_unique<EmptySet>(Z->n);
        }


constraint_reduction() used to throw when the interval contractor proves the set empty; it now returns an EmptySet instead. This is a behavioral/API change that isn’t reflected in the method docs (C++/Python) and may break callers that rely on catching the exception. Consider either preserving the exception behavior or explicitly documenting that an EmptySet may be returned when emptiness is detected.

Copilot · 2026-04-12T23:51:06Z

+    if (!Z->is_zono())
+    {
+        throw std::invalid_argument("Expected set to be a zonotope for reduce order test.");
+    }
+
+    std::unique_ptr<Zono> Z_zono (dynamic_cast<Zono*>(Z.release()));
+


The dynamic_cast is performed after Z.release(). If the cast unexpectedly fails, the raw pointer is leaked. Prefer checking/casting while the unique_ptr still owns the object (e.g., cast Z.get() and only release() after validating), or use a safer ownership transfer pattern.

Copilot · 2026-04-12T23:51:06Z

+    // convert to ConZono
+    if (!Z->is_conzono())
+    {
+        throw std::invalid_argument("Expected set to be a constrained zonotope for constraint reduction test.");
+    }
+
+    std::unique_ptr<ConZono> Z_conzono (dynamic_cast<ConZono*>(Z.release()));
+


Same issue as above: dynamic_cast after release() can leak the pointer if the cast fails. Cast/validate before releasing ownership (or restructure to avoid release() entirely).

Copilot · 2026-04-12T23:51:07Z

+    // convert to ConZono
+    if (!Z->is_conzono())
+    {
+        throw std::invalid_argument("Expected set to be a constrained zonotope for zonotope approximation test.");
+    }
+
+    std::unique_ptr<ConZono> Z_conzono (dynamic_cast<ConZono*>(Z.release()));
+


Same issue as above: dynamic_cast after release() can leak the pointer if the cast fails. Cast/validate before releasing ownership (or restructure to avoid release() entirely).

Copilot · 2026-04-12T23:51:07Z

+        assert Z.is_zono(), '_test_reduce_order: expected set to be a zonotope'
+
+        p = np.zeros(Z.get_n())
+        p_proj = Z.project_point(p)
+
+        Z_r = Z.reduce_order(10)
+


These tests validate the over-approximation property, but they don’t verify the new contract that reduce_order() returns a new object without mutating Z. Add an assertion that Z is unchanged after the call (e.g., save Z_before = Z.copy() and compare with TestUtilities.eq_hzs(Z, Z_before)).

Suggested change

assert Z.is_zono(), '_test_reduce_order: expected set to be a zonotope'

p = np.zeros(Z.get_n())

p_proj = Z.project_point(p)

Z_r = Z.reduce_order(10)

assert Z.is_zono(), '_test_reduce_order: expected set to be a zonotope'

Z_before = Z.copy()

p = np.zeros(Z.get_n())

p_proj = Z.project_point(p)

Z_r = Z.reduce_order(10)

assert TestUtilities.eq_hzs(Z, Z_before), '_test_reduce_order: reduce_order mutated the original zonotope'

Copilot · 2026-04-12T23:51:07Z

+        p_proj = Z.project_point(p)
+
+        Z_cr = Z.constraint_reduction()
+


These tests validate the over-approximation property, but they don’t verify the new contract that constraint_reduction() returns a new object without mutating Z. Add an assertion that Z is unchanged after the call (e.g., save Z_before = Z.copy() and compare with TestUtilities.eq_hzs(Z, Z_before)).

Suggested change

p_proj = Z.project_point(p)

Z_cr = Z.constraint_reduction()

p_proj = Z.project_point(p)

Z_before = Z.copy()

Z_cr = Z.constraint_reduction()

assert TestUtilities.eq_hzs(Z, Z_before), '_test_constraint_reduction: constraint_reduction mutated the original constrained zonotope'

Copilot · 2026-04-12T23:51:07Z

+
+        p = np.zeros(Z.get_n())
+        p_proj = Z.project_point(p)
+
+        Z_approx = Z.to_zono_approx()
+


These tests validate the over-approximation property, but they don’t verify the new contract that to_zono_approx() returns a new object without mutating Z. Add an assertion that Z is unchanged after the call (e.g., save Z_before = Z.copy() and compare with TestUtilities.eq_hzs(Z, Z_before)).

Suggested change

p = np.zeros(Z.get_n())

p_proj = Z.project_point(p)

Z_approx = Z.to_zono_approx()

Z_before = Z.copy()

p = np.zeros(Z.get_n())

p_proj = Z.project_point(p)

Z_approx = Z.to_zono_approx()

assert TestUtilities.eq_hzs(Z, Z_before), '_test_to_zono_approx: original constrained zonotope was mutated'

Copilot · 2026-04-12T23:51:08Z

+        Z = zono.from_json(str(overapprox_folder / 'rand_hybzono.json'))
+
+        p = np.zeros(Z.get_n())
+        p_proj = Z.project_point(p)
+
+        Z_relax = Z.convex_relaxation()
+


These tests validate the over-approximation property, but they don’t verify the new contract that convex_relaxation() returns a new object without mutating Z. Add an assertion that Z is unchanged after the call (e.g., save Z_before = Z.copy() and compare with TestUtilities.eq_hzs(Z, Z_before)).

Suggested change

Z = zono.from_json(str(overapprox_folder / 'rand_hybzono.json'))

p = np.zeros(Z.get_n())

p_proj = Z.project_point(p)

Z_relax = Z.convex_relaxation()

Z = zono.from_json(str(overapprox_folder / 'rand_hybzono.json'))

Z_before = Z.copy()

p = np.zeros(Z.get_n())

p_proj = Z.project_point(p)

Z_relax = Z.convex_relaxation()

assert TestUtilities.eq_hzs(Z, Z_before), '_test_convex_relaxation: convex_relaxation mutated the original set'

Copilot · 2026-04-12T23:51:08Z


+        std::unique_ptr<ConZono> constraint_reduction() const override
+        {
+            return std::make_unique<Zono>(*this);


This override always returns a Zono copy. For classes derived from Zono (e.g., Point), calling constraint_reduction() will slice the dynamic type and return a Zono instead of preserving the derived type (which can break is_point() checks / Python type dispatch). Consider overriding constraint_reduction() in derived classes like Point, or refactoring the base implementation to clone-preserve the dynamic type (e.g., via clone() + downcast) when no reduction is needed.

Suggested change

return std::make_unique<Zono>(*this);

return std::unique_ptr<ConZono>(static_cast<ConZono*>(this->clone()));

Josh Robbins (jrobbins11) added 3 commits April 12, 2026 15:24

constraint_reduction returns a new set rather than modifying in place

f43f1cc

added unit tests for overapproximation functions

ca1b704

regenerated documentation

1862422

Josh Robbins (jrobbins11) linked an issue Apr 12, 2026 that may be closed by this pull request

reduce_order should return a new object #53

Closed

Josh Robbins (jrobbins11) requested a review from Copilot April 12, 2026 23:45

Copilot started reviewing on behalf of Josh Robbins (jrobbins11) April 12, 2026 23:46 View session

Copilot AI reviewed Apr 12, 2026

View reviewed changes

addressing copilot PR comments

fa0e4c8

Josh Robbins (jrobbins11) merged commit 6a5e22b into main Apr 13, 2026
12 checks passed

Josh Robbins (jrobbins11) deleted the feature/mirror-remove-redundancy branch April 13, 2026 00:25

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Over-approximations return new object#57

Over-approximations return new object#57
Josh Robbins (jrobbins11) merged 4 commits intomainfrom
feature/mirror-remove-redundancy

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	return std::make_unique<Zono>(*this);
	return std::unique_ptr<ConZono>(static_cast<ConZono*>(this->clone()));

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