From: Ian Jackson <ian@davenant.relativity.greenend.org.uk>
Date: Mon, 31 Dec 2007 03:30:03 +0000 (+0000)
Subject: new edge enumeration arrangements; bugfixes
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?p=moebius2.git;a=commitdiff_plain;h=83051837693783280938bf36e9e43c7687736753

new edge enumeration arrangements; bugfixes
---

diff --git a/bgl.cpp b/bgl.cpp
index e75918a..4b06897 100644
--- a/bgl.cpp
+++ b/bgl.cpp
@@ -44,28 +44,36 @@ extern "C" {
  */
 
 #define VMASK (YMASK|XMASK)
-#define ESHIFT (YBITS|XBITS)
+#define ESHIFT (YBITS+XBITS)
 
 class Graph { }; // this is a dummy as our graph has no actual representation
 
 using namespace boost;
 
 /*
- * We use the following alternative numbering for iterating over edges:
+ * We iterate over edges in the following order:
  *
- *      ix:	    \0   /1
- *		     \  /
- *		  ___ 0   __
- *		  2    1   3
- *		     /  \
- *		   4/   5\
+ *          \#0  /1#
+ *	     \  /
+ *	  ___ 0   __
+ *	 #2    1   #3
+ *	     /  \
+ *	  #4/  #5\     and finally #6 is V6
  *
  *
- * This numbering permits the order-4 nodes at the strip's edge
- * to have a contiguous edge iterator values 2..5 or 0..3.
+ * This ordering permits the order-4 nodes at the strip's edge
+ * to have a contiguous edge iterator values.  The iterator
+ * starts at #0 which is edge 2 (see mgraph.h), or #2 (edge 3).
  */
-static const int oee_edgemap[V6]=
-  { 2<<ESHIFT, 1<<ESHIFT, 3<<ESHIFT, 2<<ESHIFT, 4<<ESHIFT, 5<<ESHIFT };
+static const int oei_edge_delta[V6]=
+  /*	 0	 1	 2	 3	 4	 5	initial e
+   *	#3	#1	#0	#2	#4	#5	initial ix
+   *	#4	#2	#1	#3	#5	#6	next ix
+   *	 4	 3	 1	 0	 5	V6	next e
+   */ {
+     4<<ESHIFT, 2<<ESHIFT, -1<<ESHIFT,
+                              -3<<ESHIFT, 1<<ESHIFT, (V6-5)<<ESHIFT
+};
 
 class OutEdgeIterator :
   public iterator_facade<
@@ -73,18 +81,24 @@ class OutEdgeIterator :
     int const,
     forward_traversal_tag
 > {
-  int v, ix, f;
-  
-  void setf() { f= v | oee_edgemap[ix]; }
+  int f;
  public:
-  void increment() { ix++; setf(); }
-  bool equal(OutEdgeIterator const& other) const { return ix == other.ix; }
+  void increment() {
+    //printf("incrementing f=%03x..",f);
+    f += oei_edge_delta[f>>ESHIFT];
+    //printf("%03x\n",f);
+  }
+  bool equal(OutEdgeIterator const& other) const { return f == other.f; }
   int const& dereference() const { return f; }
   OutEdgeIterator() { }
-  OutEdgeIterator(int _v, int _ix) : v(_v), ix(_ix) { setf(); }
+  OutEdgeIterator(int _f) : f(_f) { }
+  OutEdgeIterator(int v, int e) : f(e<<ESHIFT | v) {
+    //printf("constructed v=%x e=%x f=%03x\n",v,e,f);
+  }
 
-  static int voe_min(int _v) { return _v & YMASK ? 0 : 2; }
-  static int voe_max(int _v) { return ~_v & YMASK ? V6 : 4; }
+  static int voe_min(int _v) { return (_v & YMASK) ? 2 : 3; }
+  static int voe_max(int _v) { return (~_v & YMASK) ? V6 : 4; }
+  static int voe_degree(int _v) { return (_v & YMASK | ~_v & YMASK) ? 4 : V6; }
 };
  
 typedef counting_iterator<int> VertexIterator;
@@ -129,7 +143,7 @@ namespace boost {
 			  OutEdgeIterator(v, OutEdgeIterator::voe_max(v)));
   }
   inline unsigned out_degree(int v, const Graph&) {
-    return OutEdgeIterator::voe_max(v) - OutEdgeIterator::voe_min(v);
+    return OutEdgeIterator::voe_degree(v);
   }
 
   // Concept VertexListGraph:
diff --git a/energy.c b/energy.c
index b2ee073..89b56e2 100644
--- a/energy.c
+++ b/energy.c
@@ -247,8 +247,8 @@ static double edgewise_vertex_displacement_cost(const Vertices vertices) {
   FOR_EDGE(pi,e,qi) {
     ri= EDGE_END2(pi,(e+1)%V6); if (ri<0) continue;
     si= EDGE_END2(pi,(e+5)%V6); if (si<0) continue;
-    assert(ri == EDGE_END2(qi,(e+2)%V6));
-    assert(si == EDGE_END2(qi,(e+4)%V6));
+    /* assert(ri == EDGE_END2(qi,(e+2)%V6)); */
+    /* assert(si == EDGE_END2(qi,(e+4)%V6)); */
     
     K m[k]= (vertices[pi][k] + vertices[qi][k]) * 0.5;
     K mprime[k]= (vertices[ri][k] + vertices[si][k]) * 0.5;