From 02cffbaf13e2bc063e1b6539a62abc7841495676 Mon Sep 17 00:00:00 2001
From: Diego Talledo <38036285+talledodiego@users.noreply.github.com>
Date: Wed, 18 Mar 2026 06:57:30 +0100
Subject: [PATCH 1/3] Add InformationWarning

---
 structuralcodes/__init__.py          |  3 ++-
 structuralcodes/core/errors.py       | 14 ++++++++++++--
 structuralcodes/sections/_generic.py |  8 ++++++--
 3 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/structuralcodes/__init__.py b/structuralcodes/__init__.py
index 2e12a34a..08101845 100644
--- a/structuralcodes/__init__.py
+++ b/structuralcodes/__init__.py
@@ -4,7 +4,7 @@
 
 from . import codes, core, geometry, materials, sections
 from .codes import get_design_codes, set_design_code, set_national_annex
-from .core.errors import StructuralCodesWarning
+from .core.errors import InformationWarning, StructuralCodesWarning
 
 __version__ = '0.6.4'
 
@@ -20,3 +20,4 @@
 ]
 
 warnings.filterwarnings(action='error', category=StructuralCodesWarning)
+warnings.filterwarnings(action='always', category=InformationWarning)
diff --git a/structuralcodes/core/errors.py b/structuralcodes/core/errors.py
index 059dd6af..ba985dc8 100644
--- a/structuralcodes/core/errors.py
+++ b/structuralcodes/core/errors.py
@@ -6,6 +6,16 @@ class StructuralCodesWarning(Warning):
 
 
 class NoConvergenceWarning(StructuralCodesWarning):
-    """A warning that indicates that no convergence was reached for an
-    iterative solver.
+    """Warning for lack of convergence.
+
+    A warning that indicates that no convergence was reached for an
+    iterative solver. The solution should be inspected with care.
+    """
+
+
+class InformationWarning(StructuralCodesWarning):
+    """Warning for simple information.
+
+    A warning that indicates that some information that should be taken care
+    by user, but the calculation is not invalid.
     """
diff --git a/structuralcodes/sections/_generic.py b/structuralcodes/sections/_generic.py
index ccfe7ff9..8fdca4dc 100644
--- a/structuralcodes/sections/_generic.py
+++ b/structuralcodes/sections/_generic.py
@@ -14,7 +14,10 @@
 
 import structuralcodes.core._section_results as s_res
 from structuralcodes.core.base import Section, SectionCalculator
-from structuralcodes.core.errors import NoConvergenceWarning
+from structuralcodes.core.errors import (
+    InformationWarning,
+    NoConvergenceWarning,
+)
 from structuralcodes.geometry import (
     CompoundGeometry,
     PointGeometry,
@@ -149,7 +152,8 @@ def _calculate_gross_section_properties(self) -> s_res.SectionProperties:
         if isinstance(polygon, MultiPolygon):
             gp.perimeter = 0.0
             warnings.warn(
-                'Perimiter computation for a multi polygon is not defined.'
+                'Perimiter computation for a multi polygon is not defined.',
+                category=InformationWarning,
             )
 
         gp.perimeter = polygon.exterior.length

From 9193320934e8954725d8acb8020b2ae41ffb4bd7 Mon Sep 17 00:00:00 2001
From: Diego Talledo <38036285+talledodiego@users.noreply.github.com>
Date: Wed, 18 Mar 2026 06:58:14 +0100
Subject: [PATCH 2/3] Add test showing failing raised by #329

---
 tests/test_sections/test_generic_section.py | 30 ++++++++++++++++++++-
 1 file changed, 29 insertions(+), 1 deletion(-)

diff --git a/tests/test_sections/test_generic_section.py b/tests/test_sections/test_generic_section.py
index e862a08e..f24c8056 100644
--- a/tests/test_sections/test_generic_section.py
+++ b/tests/test_sections/test_generic_section.py
@@ -7,9 +7,13 @@
 from shapely import Polygon
 
 from structuralcodes.codes.ec2_2004 import reinforcement_duct_props
-from structuralcodes.core.errors import NoConvergenceWarning
+from structuralcodes.core.errors import (
+    InformationWarning,
+    NoConvergenceWarning,
+)
 from structuralcodes.geometry import (
     CircularGeometry,
+    CompoundGeometry,
     RectangularGeometry,
     SurfaceGeometry,
     add_reinforcement,
@@ -1993,3 +1997,27 @@ def test_section_mm_domain_warning(b, h, n_bars, diameter, fck, fyk):
 
     # Check that the results arrays have the same size
     assert len(res.m_y) == len(res_good.m_y)
+
+
+def test_perimeter_multipolygon():
+    """Test calculating the perimeter of a multipolygon.
+
+    This resoves issue #329.
+    """
+    mat = ElasticMaterial(E=210000, density=7850)
+    rect1 = SurfaceGeometry(
+        poly=Polygon([(0, 0), (100, 0), (100, 10), (0, 10)]),
+        material=mat,
+    )
+    rect2 = SurfaceGeometry(
+        poly=Polygon([(0, 200), (100, 200), (100, 210), (0, 210)]),
+        material=mat,
+    )
+
+    compound = CompoundGeometry([rect1, rect2])
+    section = GenericSection(compound, integrator='marin')
+
+    with pytest.warns(InformationWarning):
+        gp = section.gross_properties
+
+    assert math.isclose(gp.perimeter, 0)

From b91f32858c0b61f16d919aa5b248cf5e7ba19123 Mon Sep 17 00:00:00 2001
From: Diego Talledo <38036285+talledodiego@users.noreply.github.com>
Date: Wed, 18 Mar 2026 06:58:44 +0100
Subject: [PATCH 3/3] fix: correct perimeter assignment for MultiPolygon

---
 structuralcodes/sections/_generic.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/structuralcodes/sections/_generic.py b/structuralcodes/sections/_generic.py
index 8fdca4dc..2eb31ec1 100644
--- a/structuralcodes/sections/_generic.py
+++ b/structuralcodes/sections/_generic.py
@@ -155,8 +155,8 @@ def _calculate_gross_section_properties(self) -> s_res.SectionProperties:
                 'Perimiter computation for a multi polygon is not defined.',
                 category=InformationWarning,
             )
-
-        gp.perimeter = polygon.exterior.length
+        else:
+            gp.perimeter = polygon.exterior.length
 
         # Computation of area: this is taken directly from shapely
         gp.area = self.section.geometry.area