Feature: add tmp_remove_nodes method to graph (#17)

* Add .all_branches property to BaseGraphModel

Signed-off-by: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>

* Add tmp-remove-nodes method

Signed-off-by: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>

* Add .all_branches property to BaseGraphModel

Signed-off-by: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>

* Add test

Signed-off-by: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>

* Apply suggestions from code review

Co-authored-by: Vincent Koppen <vincent.koppen@alliander.com>
Signed-off-by: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>

* yield nothing

Signed-off-by: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>

* fix merge issues

Signed-off-by: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>

* make .in_edges a public method

Signed-off-by: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>

* rename method to .in_branches

Signed-off-by: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>

* remove unnecessary docstring

Signed-off-by: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>

* fix constants for graph performance tests

Signed-off-by: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>

---------

Signed-off-by: Thijs Baaijen <13253091+Thijss@users.noreply.github.com>
Co-authored-by: Vincent Koppen <vincent.koppen@alliander.com>

Author: Thijss

src/power_grid_model_ds/_core/model/graphs/models/base.py

@@ -3,6 +3,7 @@
 # SPDX-License-Identifier: MPL-2.0
 
 from abc import ABC, abstractmethod
+from contextlib import contextmanager
 from typing import Generator
 
 import numpy as np
@@ -72,6 +73,14 @@ def has_node(self, node_id: int) -> bool:
 
         return self._has_node(node_id=internal_node_id)
 
+    def in_branches(self, node_id: int) -> Generator[tuple[int, int], None, None]:
+        """Return all branches that have the node as an endpoint."""
+        int_node_id = self.external_to_internal(node_id)
+        internal_edges = self._in_branches(int_node_id=int_node_id)
+        return (
+            (self.internal_to_external(source), self.internal_to_external(target)) for source, target in internal_edges
+        )
+
     def add_node(self, ext_node_id: int, raise_on_fail: bool = True) -> None:
         """Add a node to the graph."""
         if self.has_node(ext_node_id):
@@ -173,6 +182,28 @@ def delete_branch3_array(self, branch3_array: Branch3Array, raise_on_fail: bool
             branches = _get_branch3_branches(branch3)
             self.delete_branch_array(branches, raise_on_fail=raise_on_fail)
 
+    @contextmanager
+    def tmp_remove_nodes(self, nodes: list[int]) -> Generator:
+        """Context manager that temporarily removes nodes and their branches from the graph.
+        Example:
+            >>> with graph.tmp_remove_nodes([1, 2, 3]):
+            >>>    assert not graph.has_node(1)
+            >>> assert graph.has_node(1)
+        In practice, this is useful when you want to e.g. calculate the shortest path between two nodes without
+        considering certain nodes.
+        """
+        edge_list = []
+        for node in nodes:
+            edge_list += list(self.in_branches(node))
+            self.delete_node(node)
+
+        yield
+
+        for node in nodes:
+            self.add_node(node)
+        for source, target in edge_list:
+            self.add_branch(source, target)
+
     def get_shortest_path(self, ext_start_node_id: int, ext_end_node_id: int) -> tuple[list[int], int]:
         """Calculate the shortest path between two nodes
 
@@ -279,6 +310,9 @@ def _branch_is_relevant(self, branch: BranchArray) -> bool:
             return branch.is_active.item()
         return True
 
+    @abstractmethod
+    def _in_branches(self, int_node_id: int) -> Generator[tuple[int, int], None, None]: ...
+
     @abstractmethod
     def _get_connected(self, node_id: int, nodes_to_ignore: list[int], inclusive: bool = False) -> list[int]: ...
 

src/power_grid_model_ds/_core/model/graphs/models/rustworkx.py

@@ -100,6 +100,9 @@ def _get_connected(self, node_id: int, nodes_to_ignore: list[int], inclusive: bo
 
         return connected_nodes
 
+    def _in_branches(self, int_node_id: int) -> Generator[tuple[int, int], None, None]:
+        return ((source, target) for source, target, _ in self._graph.in_edges(int_node_id))
+
     def _find_fundamental_cycles(self) -> list[list[int]]:
         """Find all fundamental cycles in the graph using Rustworkx.
 

tests/unit/model/graphs/test_graph_model.py

@@ -4,6 +4,8 @@
 
 """Grid tests"""
 
+from collections import Counter
+
 import numpy as np
 import pytest
 from numpy.testing import assert_array_equal
@@ -55,6 +57,17 @@ def test_graph_all_branches_parallel(graph):
     assert [(1, 2), (1, 2), (2, 1)] == list(graph.all_branches)
 
 
+def test_graph_in_branches(graph):
+    graph.add_node(1)
+    graph.add_node(2)
+    graph.add_branch(1, 2)
+    graph.add_branch(1, 2)
+    graph.add_branch(2, 1)
+
+    assert [(2, 1), (2, 1), (2, 1)] == list(graph.in_branches(1))
+    assert [(1, 2), (1, 2), (1, 2)] == list(graph.in_branches(2))
+
+
 def test_graph_delete_branch(graph):
     """Test whether a branch is deleted correctly"""
     graph.add_node(1)
@@ -338,3 +351,30 @@ def test_get_connected_ignore_multiple_nodes(self, graph_with_2_routes):
         connected_nodes = graph.get_connected(node_id=1, nodes_to_ignore=[2, 4])
 
         assert {5} == set(connected_nodes)
+
+
+def test_tmp_remove_nodes(graph_with_2_routes) -> None:
+    graph = graph_with_2_routes
+
+    assert graph.nr_branches == 4
+
+    # add parallel branches to test whether they are restored correctly
+    graph.add_branch(1, 5)
+    graph.add_branch(5, 1)
+
+    assert graph.nr_nodes == 5
+    assert graph.nr_branches == 6
+
+    before_sets = [frozenset(branch) for branch in graph.all_branches]
+    counter_before = Counter(before_sets)
+
+    with graph.tmp_remove_nodes([1, 2]):
+        assert graph.nr_nodes == 3
+        assert list(graph.all_branches) == [(5, 4)]
+
+    assert graph.nr_nodes == 5
+    assert graph.nr_branches == 6
+
+    after_sets = [frozenset(branch) for branch in graph.all_branches]
+    counter_after = Counter(after_sets)
+    assert counter_before == counter_after