Another performance optimization to "extresist", this one to

avoid re-parsing a linked list from the current breakpoint
to the end to find all entries pointing to the same node.
Instead, the change to be made is saved in a hash table and
applied at the following link, so only one pass through the
linked list is required.

VERSION

@@ -1 +1 @@
-8.3.646
+8.3.647

resis/ResMakeRes.c

@@ -125,7 +125,7 @@ ResCalcEastWest(tile, pendingList, doneList, resList)
     resNode	**pendingList, **doneList;
     resResistor	**resList;
 {
-    int 	height;
+    int 	count, height;
     bool	merged;
     TileType	ttype;
     Breakpoint	*p1, *p2, *p3;
@@ -134,6 +134,8 @@ ResCalcEastWest(tile, pendingList, doneList, resList)
     resNode	*currNode;
     float	rArea;
     resInfo	*info = (resInfo *)TiGetClientPTR(tile);
+    HashTable	BreakTable;
+    HashEntry	*he;
 
     merged = FALSE;
     height = TOP(tile) - BOTTOM(tile);
@@ -163,21 +165,38 @@ ResCalcEastWest(tile, pendingList, doneList, resList)
 	ttype = TiGetTypeExact(tile);
 
     /* Re-sort nodes left to right. */
+    count = ResSortBreaks(&info->breakList, TRUE);
 
-    ResSortBreaks(&info->breakList, TRUE);
+    /* For long lists (defined as >= 16 entries), make a hash table of
+     * the node pointer conversions so that each node can be updated
+     * as we walk the list, instead of walking the rest of the list in
+     * a nested loop for each entry.
+     */
+    if (count >= 16)
+	HashInit(&BreakTable, HT_DEFAULTSIZE, HT_CLIENTKEYS);
 
     /*
      * Eliminate breakpoints with the same X coordinate and merge
      * their nodes.
      */
 
-    p2= info->breakList;
+    p2 = info->breakList;
 
     /* Add extra left area to leftmost node */
 
     p2->br_this->rn_float.rn_area += height * (p2->br_loc.p_x - LEFT(tile));
     while (p2->br_next != NULL)
     {
+	/* Has the node been recorded as needing to be replaced? */
+	if (count >= 16)
+	{
+	    while (TRUE)
+	    {
+		he = HashLookOnly(&BreakTable, (char *)p2->br_this);
+		if (!he) break;
+		p2->br_this = (resNode *)HashGetValue(he);
+	    }
+	}
 	p1 = p2;
 	p2 = p2->br_next;
 	if (p2->br_loc.p_x == p1->br_loc.p_x)
@@ -215,25 +234,38 @@ ResCalcEastWest(tile, pendingList, doneList, resList)
 	    /*
 	     * Was the node used in another info or breakpoint?
 	     * If so, replace the old node with the new one.
+	     *
+	     * Short lists:  Walk the list to the end and change
+	     * nodes on the fly.
+	     * Long lists:  Record the change to be made in the
+	     * hash table so that it can be executed as each list
+	     * entry is encountered.
 	     */
-
+	    if (count >= 16)
-	    p3  = p2->br_next;
-	    while (p3 != NULL)
 	    {
-		if (p3->br_this == currNode)
+		he = HashFind(&BreakTable, (char *)currNode);
-		     p3->br_this = p2->br_this;
+		HashSetValue(he, (char *)p2->br_this);
-
-		p3 = p3->br_next;
 	    }
-       }
+	    else
+	    {
+		p3  = p2->br_next;
+		while (p3 != NULL)
+		{
+		    if (p3->br_this == currNode)
+			p3->br_this = p2->br_this;
 
-       /*
+		    p3 = p3->br_next;
-        * If the X coordinates don't match, make a resistor between
+		}
-        * the breakpoints.
+	    }
-        */
+	}
 
-       else
+	/*
-       {
+	 * If the X coordinates don't match, make a resistor between
+	 * the breakpoints.
+	 */
+
+	else
+	{
             resistor = (resResistor *)mallocMagic((unsigned)sizeof(resResistor));
             resistor->rr_nextResistor = (*resList);
             resistor->rr_lastResistor = NULL;
@@ -276,6 +308,8 @@ ResCalcEastWest(tile, pendingList, doneList, resList)
 	}
     }
 
+    if (count >= 16) HashKill(&BreakTable);
+
     p2->br_this->rn_float.rn_area += height * (RIGHT(tile) - p2->br_loc.p_x);
     freeMagic((char *)p2);
     info->breakList = NULL;
@@ -301,7 +335,7 @@ ResCalcNorthSouth(tile, pendingList, doneList, resList)
     resNode	**pendingList, **doneList;
     resResistor	**resList;
 {
-    int 	width;
+    int 	count, width;
     bool	merged;
     TileType	ttype;
     Breakpoint	*p1, *p2, *p3;
@@ -310,6 +344,8 @@ ResCalcNorthSouth(tile, pendingList, doneList, resList)
     resNode	*currNode;
     float	rArea;
     resInfo	*info = (resInfo *)TiGetClientPTR(tile);
+    HashTable	BreakTable;
+    HashEntry	*he;
 
     merged = FALSE;
     width = RIGHT(tile) - LEFT(tile);
@@ -329,7 +365,15 @@ ResCalcNorthSouth(tile, pendingList, doneList, resList)
     }
 
     /* Re-sort nodes south to north. */
-    ResSortBreaks(&info->breakList, FALSE);
+    count = ResSortBreaks(&info->breakList, FALSE);
+
+    /* For long lists (defined as >= 16 entries), make a hash table of
+     * the node pointer conversions so that each node can be updated
+     * as we walk the list, instead of walking the rest of the list in
+     * a nested loop for each entry.
+     */
+    if (count >= 16)
+	HashInit(&BreakTable, HT_DEFAULTSIZE, HT_CLIENTKEYS);
 
     /* Simplified split tile handling */
     if (IsSplit(tile))
@@ -353,6 +397,16 @@ ResCalcNorthSouth(tile, pendingList, doneList, resList)
     p2->br_this->rn_float.rn_area += width * (p2->br_loc.p_y - BOTTOM(tile));
     while (p2->br_next != NULL)
     {
+	/* Has the node been recorded as needing to be replaced? */
+	if (count >= 16)
+	{
+	    while (TRUE)
+	    {
+		he = HashLookOnly(&BreakTable, (char *)p2->br_this);
+		if (!he) break;
+		p2->br_this = (resNode *)HashGetValue(he);
+	    }
+	}
 	p1 = p2;
 	p2 = p2->br_next;
 	if (p1->br_loc.p_y == p2->br_loc.p_y)
@@ -390,14 +444,28 @@ ResCalcNorthSouth(tile, pendingList, doneList, resList)
 	    /*
 	     * Was the node used in another info or breakpoint?
 	     * If so, replace the old node with the new one.
+	     *
+	     * Short lists:  Walk the list to the end and change
+	     * nodes on the fly.
+	     * Long lists:  Record the change to be made in the
+	     * hash table so that it can be executed as each list
+	     * entry is encountered.
 	     */
-	    p3 = p2->br_next;
+	    if (count >= 16)
-	    while (p3 != NULL)
 	    {
-		if (p3->br_this == currNode)
+		he = HashFind(&BreakTable, (char *)currNode);
-		     p3->br_this = p2->br_this;
+		HashSetValue(he, (char *)p2->br_this);
+	    }
+	    else
+	    {
+		p3 = p2->br_next;
+		while (p3 != NULL)
+		{
+		    if (p3->br_this == currNode)
+			p3->br_this = p2->br_this;
 
-		p3 = p3->br_next;
+		    p3 = p3->br_next;
+		}
 	    }
 	}
 
@@ -1093,12 +1161,14 @@ MergeSortBreaks(Breakpoint *list, int xsort)
  *	bottleneck. 
  *
  * Results:
- *	None
+ *	Return the length of the list (maximum truncated at 16) so that
+ *	the calling routine can determine if this is a long or a short
+ *	linked list and treat it accordingly.
  *
  *-------------------------------------------------------------------------
  */
 
-void
+int
 ResSortBreaks(masterlist, xsort)
     Breakpoint	**masterlist;
     int		xsort;
@@ -1113,7 +1183,7 @@ ResSortBreaks(masterlist, xsort)
 	if (count > 16)
 	{
 	    *masterlist = MergeSortBreaks(*masterlist, xsort);
-	    return;
+	    return count;
 	}
     }
 
@@ -1154,5 +1224,6 @@ ResSortBreaks(masterlist, xsort)
 	    }
 	}
     }
+    return count;
 }
 

resis/resis.h

@@ -543,7 +543,7 @@ extern void			ResCheckExtNodes();
 extern void			ResSortByGate();
 extern void			ResFixDevName();
 extern void			ResWriteLumpFile();
-extern void			ResSortBreaks();
+extern int			ResSortBreaks();
 extern Plane			*extResPrepSubstrate();
 
 /* C99 compat */