maxcut_multiobjective.py

Author: WrathfulSpatula

scripts/maxcut_multiobjective.py

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+# Random MAXCUT (for execution time tests)
+# Produced by Dan Strano, Elara (the OpenAI custom GPT)
+
+from pyqrackising import maxcut_tfim_sparse, spin_glass_solver_sparse
+import networkx as nx
+import numpy as np
+import sys
+import time
+
+
+# Random heavy hex spin glass adjacency matrix
+def generate_heavy_hex_graph(
+    num_nodes=42,
+    num_edges=46,
+    mean_weight=0.0,
+    std_weight=1.0,
+    seed=None,
+):
+    """
+    Generate a random heavy-hex-like graph with Gaussian edge weights.
+    
+    Parameters
+    ----------
+    num_nodes : int
+        Number of nodes in the graph.
+    num_edges : int
+        Number of edges in the graph.
+    mean_weight : float
+        Mean of Gaussian-distributed edge weights.
+    std_weight : float
+        Standard deviation of Gaussian-distributed edge weights.
+    seed : int, optional
+        Random seed for reproducibility.
+
+    Returns
+    -------
+    G : networkx.Graph
+        Weighted heavy-hex-like graph.
+    """
+
+    rng = np.random.default_rng(seed)
+    G = nx.Graph()
+    G.add_nodes_from(range(num_nodes))
+
+    # build a pseudo-lattice backbone
+    for i in range(num_nodes - 1):
+        if rng.random() < 0.8:  # 80% chance to connect to next node
+            G.add_edge(i, (i + 1) % num_nodes)
+
+    # randomly add or remove edges to reach target edge count
+    while len(G.edges) < num_edges:
+        u, v = rng.integers(0, num_nodes, 2)
+        if u != v and not G.has_edge(u, v):
+            # Avoid too-high degree nodes (>=3) to mimic heavy hex
+            if G.degree(u) < 3 and G.degree(v) < 3:
+                G.add_edge(u, v)
+    while len(G.edges) > num_edges:
+        edge = random.choice(list(G.edges))
+        G.remove_edge(*edge)
+
+    # assign Gaussian weights
+    for u, v in G.edges:
+        G[u][v]["weight"] = rng.normal(mean_weight, std_weight)
+
+    return G
+
+
+if __name__ == "__main__":
+    seed = int(sys.argv[3]) if len(sys.argv) > 3 else 42
+
+    start = time.perf_counter()
+    G = generate_heavy_hex_graph(num_nodes=42, num_edges=46, seed=42)
+    seconds = time.perf_counter() - start
+    print(f"{seconds} seconds to initialize the graph (statement of the problem itself)")
+
+    print(f"Random seed: {seed}")
+    print(f"Node count: 42")
+    start = time.perf_counter()
+    bitstring, cut_value, cut, energy = spin_glass_solver_sparse(G, is_spin_glass=False)
+    seconds = time.perf_counter() - start
+
+    print(f"Seconds to solution: {seconds}")
+    print(f"Bipartite cut bit string: {bitstring}")
+    print(f"Cut weight: {cut_value}")