RRD - Add many new invariants/ predicates

[RandyRDavila]

No description provided.

[Copilot]

Pull request overview

This PR adds a comprehensive set of new graph invariants and predicates to the graphcalc library, organized into three new modules and several additions to existing modules.

Changes:

• Adds local invariants module with functions for computing graph parameters on neighborhood-induced subgraphs
• Adds critical invariants module with vertex/edge deletion sensitivity analysis functions
• Adds core invariants module with functions for computing the intersection of optimal solution sets
• Extends degree.py with 5 new degree-based invariants (irregularity, degree counts)
• Extends classics.py with 6 new classic graph invariants (arboricity, linear arboricity, bipartite number, average distance, path cover number)
• Extends basics.py with 2 new C4-related predicates

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 20 comments.

Show a summary per file

File	Description
local_invariants.py	New module providing local parameter evaluation on neighborhoods (703 lines) with 9 exported functions
critical_invariants.py	New module for vertex/edge deletion criticality analysis (853 lines) with helper functions for sensitivity testing
core_invariants.py	New module for computing core sets (698 lines) with functions for finding forced vertices in optimal solutions
degree.py	Added irregularity, n1_degree_count, distinct_degree_count, count_of_maximum_degree_vertices, count_of_minimum_degree_vertices
classics.py	Added bipartite_number, average_distance, path_cover_number, arboricity, linear_arboricity with supporting helpers
basics.py	Added is_C4_free and is_induced_C4_free predicates for detecting 4-cycles
init.py	Added imports for the three new modules

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[Copilot]

The function call in this example is missing the module prefix. It should be gc.n1_degree_count(G) to be consistent with other examples in this file.

Suggested change

	>>> n1_degree_count(G)
	>>> gc.n1_degree_count(G)

[Copilot]

The function calls in these examples are missing the module prefix. They should be gc.count_of_minimum_degree_vertices(G) and gc.count_of_minimum_degree_vertices(H) to be consistent with other examples in this file.

Suggested change

	>>> count_of_minimum_degree_vertices(G)
	2
	>>> H = nx.empty_graph(4) # all degrees 0
	>>> count_of_minimum_degree_vertices(H)
	>>> gc.count_of_minimum_degree_vertices(G)
	2
	>>> H = nx.empty_graph(4) # all degrees 0
	>>> gc.count_of_minimum_degree_vertices(H)

[Copilot]

The function calls in these examples are missing the module prefix. They should be gc.path_cover_number(G), gc.path_cover_number(H), and gc.path_cover_number(J) to be consistent with the established pattern in this codebase.

Suggested change

	>>> # A path is coverable by a single path
	>>> G = nx.path_graph(6)
	>>> path_cover_number(G)
	1
	>>> # An edgeless graph on n vertices needs n singleton paths
	>>> H = nx.empty_graph(5)
	>>> path_cover_number(H)
	5
	>>> # Two disjoint paths need two paths in the cover
	>>> J = nx.disjoint_union(nx.path_graph(3), nx.path_graph(4))
	>>> path_cover_number(J)
	>>> import graphcalc as gc
	>>> # A path is coverable by a single path
	>>> G = nx.path_graph(6)
	>>> gc.path_cover_number(G)
	1
	>>> # An edgeless graph on n vertices needs n singleton paths
	>>> H = nx.empty_graph(5)
	>>> gc.path_cover_number(H)
	5
	>>> # Two disjoint paths need two paths in the cover
	>>> J = nx.disjoint_union(nx.path_graph(3), nx.path_graph(4))
	>>> gc.path_cover_number(J)

[Copilot]

Pull request overview

Copilot reviewed 33 out of 33 changed files in this pull request and generated 9 comments.

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[Copilot]

Pull request overview

Copilot reviewed 34 out of 35 changed files in this pull request and generated 3 comments.

---

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[Copilot]

Duplicate import: List is imported twice from the typing module on consecutive lines. The second import on line 3 also imports Sequence, making the first import redundant. Remove line 2.

[Copilot]

Inefficiency: gc.degree(G, v) and gc.degree(G, u) are called for every edge. This makes O(m) degree lookups where m is the number of edges, which could be expensive. Consider pre-computing degrees once:

deg = dict(G.degree())
return 2*sum(1/(deg[u] + deg[v]) for u, v in G.edges())

This pattern is used correctly in other index functions in this same file (e.g., randic_index line 94-95).

Suggested change

	return 2*sum((1/(gc.degree(G, v) + gc.degree(G, u)) for u, v in G.edges()))
	deg = dict(G.degree())
	return 2 * sum(1 / (deg[u] + deg[v]) for u, v in G.edges())

[Copilot]

Module 'graphcalc' is imported with both 'import' and 'import from'.

Suggested change

import graphcalc as gc