add class for online centroid computation

test/python/utils/test_centroid.py

@@ -0,0 +1,56 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# This file is part of Nominatim. (https://nominatim.org)
+#
+# Copyright (C) 2022 by the Nominatim developer community.
+# For a full list of authors see the git log.
+"""
+Tests for centroid computation.
+"""
+import pytest
+
+from nominatim.utils.centroid import PointsCentroid
+
+def test_empty_set():
+    c = PointsCentroid()
+
+    with pytest.raises(ValueError, match='No points'):
+        c.centroid()
+
+
+@pytest.mark.parametrize("centroid", [(0,0), (-1, 3), [0.0000032, 88.4938]])
+def test_one_point_centroid(centroid):
+    c = PointsCentroid()
+
+    c += centroid
+
+    assert len(c.centroid()) == 2
+    assert c.centroid() == (pytest.approx(centroid[0]), pytest.approx(centroid[1]))
+
+
+def test_multipoint_centroid():
+    c = PointsCentroid()
+
+    c += (20.0, -10.0)
+    assert c.centroid() == (pytest.approx(20.0), pytest.approx(-10.0))
+    c += (20.2, -9.0)
+    assert c.centroid() == (pytest.approx(20.1), pytest.approx(-9.5))
+    c += (20.2, -9.0)
+    assert c.centroid() == (pytest.approx(20.13333), pytest.approx(-9.333333))
+
+
+def test_manypoint_centroid():
+    c = PointsCentroid()
+
+    for _ in range(10000):
+        c += (4.564732, -0.000034)
+
+    assert c.centroid() == (pytest.approx(4.564732), pytest.approx(-0.000034))
+
+
+@pytest.mark.parametrize("param", ["aa", None, 5, [1, 2, 3], (3, None), ("a", 3.9)])
+def test_add_non_tuple(param):
+    c = PointsCentroid()
+
+    with pytest.raises(ValueError, match='2-element tuples'):
+        c += param