From 18d874a96a994ad1c077d11801608016cdbe35e5 Mon Sep 17 00:00:00 2001
From: Matt Guthaus <mrg@ucsc.edu>
Date: Wed, 14 Nov 2018 10:05:04 -0800
Subject: [PATCH] Fix error in iterative implementation of combine_classes

---
 compiler/router/router.py | 41 ++++++++++++---------------------------
 1 file changed, 12 insertions(+), 29 deletions(-)

diff --git a/compiler/router/router.py b/compiler/router/router.py
index 245b5878..18d88df7 100644
--- a/compiler/router/router.py
+++ b/compiler/router/router.py
@@ -653,48 +653,31 @@ class router(router_tech):
         debug.info(2,"Analyzing pin groups for {}.".format(pin_name))        
         
         pin_set = self.pins[pin_name]
-        local_debug = False
 
         # Put each pin in an equivalence class of it's own
         equiv_classes = [set([x]) for x in pin_set]
-        if local_debug:
-            debug.info(0,"INITIAL\n"+pformat(equiv_classes))
-
-        first_run = True
-        while (first_run or len(equiv_classes)<len(old_equiv_classes)):
-            first_run=False
+        def combine_classes(equiv_classes):
             for class1 in equiv_classes:
                 for class2 in equiv_classes:
                     if class1 == class2:
                         continue
-                    #class3 = compare_classes(class1, class2)
                     # Compare each pin in each class,
-                    # and if any overlap, return the combined the class
-                    combined_class = None
+                    # and if any overlap, update equiv_classes to include the combined the class
                     for p1 in class1:
                         for p2 in class2:
                             if p1.overlaps(p2):
                                 combined_class = class1 | class2
-                                if local_debug:
-                                    debug.info(0,"COMBINE:"+pformat(combined_class))
-                                break
-                        else:
-                            continue
-                        break
-                                    
-                    if combined_class:
-                        old_equiv_classes = equiv_classes
-                        equiv_classes.remove(class1)
-                        equiv_classes.remove(class2)
-                        equiv_classes.append(combined_class)
-                        break
-                else:
-                    continue
-                break
-                            
+                                equiv_classes.remove(class1)
+                                equiv_classes.remove(class2)
+                                equiv_classes.append(combined_class)
+                                return(equiv_classes)
+            return(equiv_classes)
+
+        old_length = math.inf
+        while (len(equiv_classes)<old_length):
+            old_length = len(equiv_classes)
+            equiv_classes = combine_classes(equiv_classes)
 
-        if local_debug:
-            debug.info(0,"FINAL  "+pformat(equiv_classes))
         self.pin_groups[pin_name] = [pin_group(name=pin_name, pin_set=x, router=self) for x in equiv_classes]
         
     def convert_pins(self, pin_name):