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Memory leak when using unary_union

See original GitHub issue

When using unary_union it seems that some memory leaks occur.

For example when running the above code the virtual memory used by the python process increase continuously.

from shapely.geometry import Polygon, LineString
from shapely.ops import unary_union

a = Polygon([(0, 0), (0, 1), (1, 1), (1, 0)])
b = LineString([(0, 0), (1, 1)])
for _ in range(1000000):
    c = unary_union((a, b))

I am facing the issue on a CentOS 7 machine, with Python3, Shapely 1.6.4.post2 (from pip) and Proj 4.8.0.

EDIT: the same append with cascaded_union

Issue Analytics

State:
Created 4 years ago
Comments:14 (8 by maintainers)

Top GitHub Comments

1reaction

sgilliescommented, Aug 18, 2020

Confirmed. I ran the code under valgrind with 100 loops and I see

==22834== 8,000 (6,400 direct, 1,600 indirect) bytes in 100 blocks are definitely lost in loss record 4,274 of 4,288
==22834==    at 0x4C3017F: operator new(unsigned long) (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==22834==    by 0x90B9264: geos::geom::GeometryFactory::createMultiPolygon(std::vector<geos::geom::Geometry*, std::allocator<geos::geom::Geometry*> >*) const (in /home/sean/.local/pipx/venvs/fiona/lib/python3.7/site-packages/shapely/.libs/libgeos--no-undefined-fab82081.so)
==22834==    by 0x8AB63A8: GEOSGeom_createCollection_r (in /home/sean/.local/pipx/venvs/fiona/lib/python3.7/site-packages/shapely/.libs/libgeos_c-5031f9ac.so.1.13.1)
==22834==    by 0x6D42DAD: ffi_call_unix64 (in /usr/lib/x86_64-linux-gnu/libffi.so.6.0.4)
==22834==    by 0x6D4271E: ffi_call (in /usr/lib/x86_64-linux-gnu/libffi.so.6.0.4)
==22834==    by 0x6B2F943: _ctypes_callproc (in /usr/lib/python3.7/lib-dynload/_ctypes.cpython-37m-x86_64-linux-gnu.so)
==22834==    by 0x6B300D3: ??? (in /usr/lib/python3.7/lib-dynload/_ctypes.cpython-37m-x86_64-linux-gnu.so)
==22834==    by 0x5DBBC5: PyObject_Call (in /usr/bin/python3.7)
==22834==    by 0x622A92: ??? (in /usr/bin/python3.7)
==22834==    by 0x5D96DA: _PyObject_FastCallKeywords (in /usr/bin/python3.7)
==22834==    by 0x54AA50: ??? (in /usr/bin/python3.7)
==22834==    by 0x551C07: _PyEval_EvalFrameDefault (in /usr/bin/python3.7)

0reactions

sgilliescommented, Nov 3, 2021

Meanwhile, the work around is to use union in such a loop, or call unary_union once with a list of all source geometries, which is its intended use.

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