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Feature/improved welding #157

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430f269
Add drop_detours opteration
p-snft Dec 2, 2025
aa5e1f0
Merge branch 'dev' into feature/improved_welding
p-snft Dec 2, 2025
581149b
Add pure networkx based simplification functions
p-snft Dec 5, 2025
8127611
Improve graph simplification functions
p-snft Dec 8, 2025
4b7c171
Add missing blank line (Black)
p-snft Dec 8, 2025
ab8eda3
Fix import order in test_gistools
p-snft Dec 8, 2025
12086f8
Add via bookkeeping for merging edges
p-snft Dec 15, 2025
38d96f4
Add distance calcuation in gistools
p-snft Feb 3, 2026
d6b85b3
Merge branch 'feature/improved_welding' of github.com:oemof/DHNx into…
p-snft Feb 3, 2026
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2 changes: 2 additions & 0 deletions src/dhnx/gistools/connect_points.py
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Original file line number Diff line number Diff line change
Expand Up @@ -724,6 +724,8 @@ def process_geometry(
# Convert all MultiLineStrings to LineStrings
check_geometry_type(lines_all, types=["LineString"])

go.drop_detours(lines_all)

# ## check for near points
go.check_double_points(points_all, id_column="id_full")

Expand Down
153 changes: 152 additions & 1 deletion src/dhnx/gistools/geometry_operations.py
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Original file line number Diff line number Diff line change
Expand Up @@ -13,12 +13,15 @@
SPDX-License-Identifier: MIT
"""

import math

try:
import geopandas as gpd

except ImportError:
print("Need to install geopandas to process geometry data.")

import networkx as nx

try:
import shapely
from shapely import wkt
Expand Down Expand Up @@ -629,6 +632,154 @@ def drop_parallel_lines(gdf):
return gdf


def drop_detours(lines_all):
"""Keep only lines that are the shortest connections between two points.
"""
graph = nx.Graph()
graph.add_edges_from([
(a, b, {"weight": length})
for a, b, length
in zip(
lines_all["from_node"],
lines_all["to_node"],
lines_all["length"],
)
])

# identify rows contaning "detour" lines
lines_to_drop = []
for row, line in lines_all.iterrows():
if line["length"] > nx.shortest_path_length(
graph,
source=line["from_node"],
target=line["to_node"],
weight="weight",
):
lines_to_drop.append(row)

lines_all.drop(lines_to_drop, inplace=True)

return lines_all


def simplify_graph(
graph: nx.Graph,
) -> bool:
graph_was_updated = False
graph_needs_iteration = True
while graph_needs_iteration:
graph_needs_iteration = False
detours_dropped = _drop_detours(graph)
forks_removed = _remove_useless_forks(graph)

# if something changed, we need a new iteration
graph_needs_iteration = detours_dropped or forks_removed

# graph was updated if new iteration is needed or it was updated before
graph_was_updated = graph_needs_iteration or graph_was_updated

return graph_was_updated


def annotate_distance(
graph: nx.Graph,
) -> None:
"""Inefficient algorithm that doesthe job."""
for source in list(graph.nodes()):
source_type = graph.nodes[source]["type"]
for target in list(graph.nodes()):
target_type = graph.nodes[target]["type"]
if source_type != target_type:
source_distance = graph.nodes[source].get("distance", math.inf)
target_distance = graph.nodes[target].get("distance", math.inf)
path_length = nx.shortest_path_length(
graph,
source=source,
target=target,
weight="weight",
)
graph.nodes[source]["distance"] = min(
path_length, source_distance
)
graph.nodes[target]["distance"] = min(
path_length, target_distance
)


def longest_distance(
graph: nx.Graph,
) -> float:
_longest_distance = 0.0
for source in list(graph.nodes()):
if graph.nodes[source]['type'] != "fork":
for target in list(graph.nodes()):
if graph.nodes[target]['type'] != "fork":
_longest_distance = max(
_longest_distance,
nx.shortest_path_length(
graph,
source=source,
target=target,
weight="weight",
),
)
return _longest_distance


def _drop_detours(
graph: nx.Graph,
) -> bool:
graph_was_updated = False
for (source, target) in list(graph.edges()):
edge_weight = graph[source][target]["weight"]
if edge_weight > nx.shortest_path_length(
graph,
source=source,
target=target,
weight="weight",
):
graph.remove_edge(source, target)
graph_was_updated = True

return graph_was_updated


def _remove_useless_forks(
graph: nx.Graph,
) -> bool:
"""Removes forks that only connect two lines as well as dead ends.

You need to iterate to also remove forks
that connected dead ends to meaningful lines.
"""
graph_was_updated = False
for node in list(graph.nodes()):
if graph.nodes[node]['type'] == "fork":
if graph.degree(node) == 1:
graph.remove_node(node)
graph_was_updated = True
elif graph.degree(node) == 2:
edges = list(graph.edges(node))
edge_weight = (
graph[edges[0][0]][edges[0][1]]["weight"]
+ graph[edges[1][0]][edges[1][1]]["weight"]
)
via = (
graph[edges[0][0]][edges[0][1]].get("via", [edges[0]])
+ graph[edges[1][0]][edges[1][1]].get("via", [edges[1]])
)

graph.add_edge(
edges[0][1],
edges[1][1],
weight=edge_weight,
via=via,
)
graph.remove_node(node)
graph_was_updated = True
return graph_was_updated


def check_crs(gdf, crs=4647, force_2d=True):
"""Convert CRS to EPSG:4647 - ETRS89 / UTM zone 32N (zE-N).

Expand Down
73 changes: 73 additions & 0 deletions tests/test_gistools.py
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,7 @@
"""

import geopandas as gpd
import networkx as nx
from shapely.geometry import LineString
from shapely.geometry import MultiLineString
from shapely.geometry import Point
Expand All @@ -35,3 +36,75 @@
results = go.split_multilinestr_to_linestr(gdf_line)
assert gdf_line.geometry.length.sum() == results.length.sum()
assert len(results.index) == 7


def test_drop_detours():
edgelist = [
(0, 1, {"weight": 5}),
(1, 2, {"weight": 2}),
(2, 0, {"weight": 2}),
]
graph = nx.Graph(edgelist)

go._drop_detours(graph)

# longer connection with direct edge has been dropped
assert list(graph.edges()) == [(0, 2), (1, 2)]

nodelist = [

Check failure on line 54 in tests/test_gistools.py

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tests/test_gistools.py#L54 

Expected 2 blank lines after class or function definition, found 1 (E305)
(0, {"type": "fork"}),
(1, {"type": "fork"}),
(2, {"type": "fork"}),
(3, {"type": "fork"}),
(4, {"type": "fork"}),
("s1", {"type": "sink"}),
("s2", {"type": "sink"}),
]
edgelist = [
("s1", 0, {"weight": 1}),
(0, 1, {"weight": 5}),
(1, 2, {"weight": 2}),
(2, 4, {"weight": 7}),
(2, 3, {"weight": 2}),
("s2", 3, {"weight": 1}),
]


def test_annotate_distance():
graph = nx.Graph()
graph.add_nodes_from(nodelist)
graph.add_edges_from(edgelist)
go.annotate_distance(graph)

distances = {
0: 1,
1: 5,
2: 3,
3: 1,
4: 10,
"s1": 1,
"s2": 1,
}
node_list = list(graph.nodes())
for node in node_list:
assert graph.nodes[node]["distance"] == distances[node]


def test_longest_distance():
graph = nx.Graph()
graph.add_nodes_from(nodelist)
graph.add_edges_from(edgelist)

assert go.longest_distance(graph) == 5 + 2 + 2 + 1 + 1


def test_remove_useless_forks():
graph = nx.Graph()
graph.add_nodes_from(nodelist)
graph.add_edges_from(edgelist)
graph_was_updated = go.simplify_graph(graph)

assert graph_was_updated
assert list(graph.edges()) == [("s1", "s2")]
assert len(graph["s1"]["s2"]["via"]) == 5
assert graph["s1"]["s2"]["weight"] == 1 + 5 + 2 + 2 + 1
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