From 604b49053b39b328e47ca3119b171ae01a0047c3 Mon Sep 17 00:00:00 2001
From: Simon Bjurek <simbj106@student.liu.se>
Date: Thu, 3 Apr 2025 11:39:21 +0200
Subject: [PATCH] added pre-solver heuristic to improve performance of ILP
resource allocation, also added extra constraint to improve performance
---
b_asic/resources.py | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/b_asic/resources.py b/b_asic/resources.py
index 5c5f426e..df2b34df 100644
--- a/b_asic/resources.py
+++ b/b_asic/resources.py
@@ -1347,8 +1347,11 @@ class ProcessCollection:
nodes = list(exclusion_graph.nodes())
edges = list(exclusion_graph.edges())
- # determine an upper bound on the number of colors
- max_colors = len(nodes)
+ # run a good heuristic to get an upper bound on the amount of colors
+ coloring = nx.coloring.greedy_color(
+ exclusion_graph, strategy="saturation_largest_first"
+ )
+ max_colors = len(set(coloring.values()))
# binary variables:
# x[node, color] - whether node is colored in a certain color
@@ -1364,6 +1367,7 @@ class ProcessCollection:
# 1 - nodes have exactly one color
# 2 - adjacent nodes cannot have the same color
# 3 - only permit assignments if color is used
+ # 4 - reduce solution space by setting the color of one node
for node in nodes:
problem += lpSum(x[node][i] for i in range(max_colors)) == 1
for u, v in edges:
@@ -1372,6 +1376,7 @@ class ProcessCollection:
for node in nodes:
for color in range(max_colors):
problem += x[node][color] <= c[color]
+ problem += x[nodes[0]][0] == c[0] == 1
status = problem.solve()
--
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