diff --git a/fa2/fa2util.c b/fa2/fa2util.c
index 4797b03..406d8f8 100644
--- a/fa2/fa2util.c
+++ b/fa2/fa2util.c
@@ -1,4 +1,4 @@
-/* Generated by Cython 0.29.12 */
+/* Generated by Cython 0.29.15 */
 
 #define PY_SSIZE_T_CLEAN
 #include "Python.h"
@@ -7,9 +7,9 @@
 #elif PY_VERSION_HEX < 0x02060000 || (0x03000000 <= PY_VERSION_HEX && PY_VERSION_HEX < 0x03030000)
     #error Cython requires Python 2.6+ or Python 3.3+.
 #else
-#define CYTHON_ABI "0_29_12"
-#define CYTHON_HEX_VERSION 0x001D0CF0
-#define CYTHON_FUTURE_DIVISION 1
+#define CYTHON_ABI "0_29_15"
+#define CYTHON_HEX_VERSION 0x001D0FF0
+#define CYTHON_FUTURE_DIVISION 0
 #include <stddef.h>
 #ifndef offsetof
   #define offsetof(type, member) ( (size_t) & ((type*)0) -> member )
@@ -801,9 +801,9 @@ static const char *__pyx_filename;
 
 
 static const char *__pyx_f[] = {
-  "fa2/fa2util.py",
-  "fa2/fa2util.pxd",
+  "fa2util.pxd",
   "stringsource",
+  "fa2util.py",
 };
 
 /*--- Type declarations ---*/
@@ -878,7 +878,7 @@ struct __pyx_opt_args_3fa2_7fa2util_apply_gravity {
   int useStrongGravity;
 };
 
-/* "fa2/fa2util.pxd":102
+/* "fa2/fa2util.pxd":100
  *     @cython.locals(distance = cython.double,
  *                    subregion = Region)
  *     cdef void applyForce(self, Node n, double theta, double coefficient=*)             # <<<<<<<<<<<<<<
@@ -890,7 +890,7 @@ struct __pyx_opt_args_3fa2_7fa2util_6Region_applyForce {
   double coefficient;
 };
 
-/* "fa2/fa2util.pxd":105
+/* "fa2/fa2util.pxd":103
  * 
  *     @cython.locals(n = Node)
  *     cpdef applyForceOnNodes(self, list nodes, double theta, double coefficient=*)             # <<<<<<<<<<<<<<
@@ -1036,16 +1036,6 @@ static struct __pyx_vtabstruct_3fa2_7fa2util_Region *__pyx_vtabptr_3fa2_7fa2util
 #define __Pyx_CLEAR(r)    do { PyObject* tmp = ((PyObject*)(r)); r = NULL; __Pyx_DECREF(tmp);} while(0)
 #define __Pyx_XCLEAR(r)   do { if((r) != NULL) {PyObject* tmp = ((PyObject*)(r)); r = NULL; __Pyx_DECREF(tmp);}} while(0)
 
-/* PyObjectGetAttrStr.proto */
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-static CYTHON_INLINE PyObject* __Pyx_PyObject_GetAttrStr(PyObject* obj, PyObject* attr_name);
-#else
-#define __Pyx_PyObject_GetAttrStr(o,n) PyObject_GetAttr(o,n)
-#endif
-
-/* GetBuiltinName.proto */
-static PyObject *__Pyx_GetBuiltinName(PyObject *name);
-
 /* RaiseArgTupleInvalid.proto */
 static void __Pyx_RaiseArgtupleInvalid(const char* func_name, int exact,
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@@ -1097,12 +1087,22 @@ static CYTHON_INLINE void __Pyx_ErrFetchInState(PyThreadState *tstate, PyObject
 #define __Pyx_ErrFetch(type, value, tb)  PyErr_Fetch(type, value, tb)
 #endif
 
+/* PyObjectGetAttrStr.proto */
+#if CYTHON_USE_TYPE_SLOTS
+static CYTHON_INLINE PyObject* __Pyx_PyObject_GetAttrStr(PyObject* obj, PyObject* attr_name);
+#else
+#define __Pyx_PyObject_GetAttrStr(o,n) PyObject_GetAttr(o,n)
+#endif
+
 /* GetAttr.proto */
 static CYTHON_INLINE PyObject *__Pyx_GetAttr(PyObject *, PyObject *);
 
 /* GetAttr3.proto */
 static CYTHON_INLINE PyObject *__Pyx_GetAttr3(PyObject *, PyObject *, PyObject *);
 
+/* GetBuiltinName.proto */
+static PyObject *__Pyx_GetBuiltinName(PyObject *name);
+
 /* PyDictVersioning.proto */
 #if CYTHON_USE_DICT_VERSIONS && CYTHON_USE_TYPE_SLOTS
 #define __PYX_DICT_VERSION_INIT  ((PY_UINT64_T) -1)
@@ -1432,12 +1432,22 @@ static void __Pyx_AddTraceback(const char *funcname, int c_line,
 /* CIntToPy.proto */
 static CYTHON_INLINE PyObject* __Pyx_PyInt_From_int(int value);
 
+/* Print.proto */
+static int __Pyx_Print(PyObject*, PyObject *, int);
+#if CYTHON_COMPILING_IN_PYPY || PY_MAJOR_VERSION >= 3
+static PyObject* __pyx_print = 0;
+static PyObject* __pyx_print_kwargs = 0;
+#endif
+
 /* CIntToPy.proto */
 static CYTHON_INLINE PyObject* __Pyx_PyInt_From_long(long value);
 
 /* CIntFromPy.proto */
 static CYTHON_INLINE int __Pyx_PyInt_As_int(PyObject *);
 
+/* PrintOne.proto */
+static int __Pyx_PrintOne(PyObject* stream, PyObject *o);
+
 /* CIntFromPy.proto */
 static CYTHON_INLINE long __Pyx_PyInt_As_long(PyObject *);
 
@@ -1491,15 +1501,16 @@ extern int __pyx_module_is_main_fa2__fa2util;
 int __pyx_module_is_main_fa2__fa2util = 0;
 
 /* Implementation of 'fa2.fa2util' */
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 static const char __pyx_k_e[] = "e";
 static const char __pyx_k_n1[] = "n1";
 static const char __pyx_k_n2[] = "n2";
+static const char __pyx_k_end[] = "end";
 static const char __pyx_k_inf[] = "inf";
 static const char __pyx_k_new[] = "__new__";
 static const char __pyx_k_Edge[] = "Edge";
 static const char __pyx_k_Node[] = "Node";
 static const char __pyx_k_dict[] = "__dict__";
+static const char __pyx_k_file[] = "file";
 static const char __pyx_k_main[] = "__main__";
 static const char __pyx_k_math[] = "math";
 static const char __pyx_k_name[] = "__name__";
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 static const char __pyx_k_setstate[] = "__setstate__";
 static const char __pyx_k_pyx_state[] = "__pyx_state";
 static const char __pyx_k_reduce_ex[] = "__reduce_ex__";
+static const char __pyx_k_fa2util_py[] = "fa2util.py";
 static const char __pyx_k_pyx_result[] = "__pyx_result";
 static const char __pyx_k_pyx_vtable[] = "__pyx_vtable__";
 static const char __pyx_k_PickleError[] = "PickleError";
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 static const char __pyx_k_apply_gravity[] = "apply_gravity";
 static const char __pyx_k_linAttraction[] = "linAttraction";
 static const char __pyx_k_reduce_cython[] = "__reduce_cython__";
-static const char __pyx_k_fa2_fa2util_py[] = "fa2/fa2util.py";
 static const char __pyx_k_apply_repulsion[] = "apply_repulsion";
 static const char __pyx_k_buildSubRegions[] = "buildSubRegions";
 static const char __pyx_k_jitterTolerance[] = "jitterTolerance";
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 static PyObject *__pyx_kp_s_Incompatible_checksums_s_vs_0x66;
 static PyObject *__pyx_kp_s_Incompatible_checksums_s_vs_0xb4;
-static PyObject *__pyx_kp_u_No_cython_detected_Install_cytho;
+static PyObject *__pyx_kp_s_No_cython_detected_Install_cytho;
 static PyObject *__pyx_n_s_Node;
 static PyObject *__pyx_n_s_Node___reduce_cython;
 static PyObject *__pyx_n_s_Node___setstate_cython;
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 static PyObject *__pyx_n_s_Region___setstate_cython;
 static PyObject *__pyx_n_s_Region_applyForceOnNodes;
 static PyObject *__pyx_n_s_Region_buildSubRegions;
-static PyObject *__pyx_kp_u_Warning_uncompiled_fa2util_modul;
+static PyObject *__pyx_kp_s_Warning_uncompiled_fa2util_modul;
 static PyObject *__pyx_n_s_adjustSpeedAndApplyForces;
 static PyObject *__pyx_n_s_applyForceOnNodes;
 static PyObject *__pyx_n_s_apply_attraction;
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 static PyObject *__pyx_n_s_e;
 static PyObject *__pyx_n_s_edgeWeightInfluence;
 static PyObject *__pyx_n_s_edges;
+static PyObject *__pyx_n_s_end;
 static PyObject *__pyx_n_s_fa2_fa2util;
-static PyObject *__pyx_kp_s_fa2_fa2util_py;
+static PyObject *__pyx_kp_s_fa2util_py;
+static PyObject *__pyx_n_s_file;
 static PyObject *__pyx_n_s_getstate;
 static PyObject *__pyx_n_s_gravity;
 static PyObject *__pyx_n_s_import;
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 static PyObject *__pyx_n_s_jitterTolerance;
 static PyObject *__pyx_n_s_linAttraction;
 static PyObject *__pyx_n_s_main;
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 static PyObject *__pyx_n_s_setstate;
 static PyObject *__pyx_n_s_setstate_cython;
 static PyObject *__pyx_n_s_speed;
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 static PyObject *__pyx_n_s_speedEfficiency;
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 static PyObject *__pyx_n_s_sqrt;
 static PyObject *__pyx_n_s_state;
 static PyObject *__pyx_kp_s_stringsource;
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 static PyObject *__pyx_tuple__25;
 static PyObject *__pyx_tuple__27;
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 /* Late includes */
 
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-        /* "fa2/fa2util.py":198
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- *             for n in rightNodes:
- *                 if n.y < self.massCenterY:             # <<<<<<<<<<<<<<
- *                     toprightNodes.append(n)
+          /* "fa2/fa2util.py":192
+ *                         topleftNodes.append(n)
  *                 else:
+ *                     if n.y < self.massCenterY:             # <<<<<<<<<<<<<<
+ *                         bottomrightNodes.append(n)
+ *                     else:
  */
-        goto __pyx_L12;
-      }
+          goto __pyx_L8;
+        }
 
-      /* "fa2/fa2util.py":201
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- *                 else:
- *                     bottomrightNodes.append(n)             # <<<<<<<<<<<<<<
+        /* "fa2/fa2util.py":195
+ *                         bottomrightNodes.append(n)
+ *                     else:
+ *                         toprightNodes.append(n)             # <<<<<<<<<<<<<<
  * 
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  */
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+        /*else*/ {
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+        }
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-      __pyx_L12:;
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- *             for n in rightNodes:             # <<<<<<<<<<<<<<
- *                 if n.y < self.massCenterY:
- *                     toprightNodes.append(n)
+      /* "fa2/fa2util.py":185
+ *             # subregions now requires only one for loop. Removed
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+ *                 if n.x < self.massCenterX:
+ *                     if n.y < self.massCenterY:
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     }
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-    /* "fa2/fa2util.py":203
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-        /* "fa2/fa2util.py":205
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-        /* "fa2/fa2util.py":206
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-        /* "fa2/fa2util.py":204
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-          /* "fa2/fa2util.py":210
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-          __pyx_t_3 = PyList_New(1); if (unlikely(!__pyx_t_3)) __PYX_ERR(0, 218, __pyx_L1_error)
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-          /* "fa2/fa2util.py":219
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-          /* "fa2/fa2util.py":217
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@@ -6114,9 +6019,9 @@ static void __pyx_f_3fa2_7fa2util_6Region_buildSubRegions(struct __pyx_obj_3fa2_
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@@ -6125,49 +6030,49 @@ static void __pyx_f_3fa2_7fa2util_6Region_buildSubRegions(struct __pyx_obj_3fa2_
  */
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-        /* "fa2/fa2util.py":223
+        /* "fa2/fa2util.py":217
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-        /* "fa2/fa2util.py":224
+        /* "fa2/fa2util.py":218
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-          __PYX_ERR(0, 224, __pyx_L1_error)
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-        /* "fa2/fa2util.py":222
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-        goto __pyx_L22;
+        goto __pyx_L18;
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-      /* "fa2/fa2util.py":226
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@@ -6202,34 +6107,34 @@ static void __pyx_f_3fa2_7fa2util_6Region_buildSubRegions(struct __pyx_obj_3fa2_
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-          /* "fa2/fa2util.py":227
+          /* "fa2/fa2util.py":221
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-          __pyx_t_2 = PyList_New(1); if (unlikely(!__pyx_t_2)) __PYX_ERR(0, 227, __pyx_L1_error)
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-          __pyx_t_3 = __Pyx_PyObject_CallOneArg(((PyObject *)__pyx_ptype_3fa2_7fa2util_Region), __pyx_t_2); if (unlikely(!__pyx_t_3)) __PYX_ERR(0, 227, __pyx_L1_error)
+          __pyx_t_3 = __Pyx_PyObject_CallOneArg(((PyObject *)__pyx_ptype_3fa2_7fa2util_Region), __pyx_t_2); if (unlikely(!__pyx_t_3)) __PYX_ERR(2, 221, __pyx_L1_error)
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-          /* "fa2/fa2util.py":228
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  *                     for n in toprightNodes:
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-          /* "fa2/fa2util.py":226
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  */
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-        /* "fa2/fa2util.py":232
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-          /* "fa2/fa2util.py":236
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+          __pyx_t_2 = __Pyx_PyObject_CallOneArg(((PyObject *)__pyx_ptype_3fa2_7fa2util_Region), __pyx_t_3); if (unlikely(!__pyx_t_2)) __PYX_ERR(2, 230, __pyx_L1_error)
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-          /* "fa2/fa2util.py":237
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-  /* "fa2/fa2util.py":273
+  /* "fa2/fa2util.py":267
  *     # networks need less tolerance. Totally empiric.
  *     estimatedOptimalJitterTolerance = .05 * sqrt(len(nodes))
  *     minJT = sqrt(estimatedOptimalJitterTolerance)             # <<<<<<<<<<<<<<
  *     maxJT = 10
  *     jt = jitterTolerance * max(minJT,
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-  __Pyx_GetModuleGlobalName(__pyx_t_1, __pyx_n_s_sqrt); if (unlikely(!__pyx_t_1)) __PYX_ERR(0, 273, __pyx_L1_error)
+  __Pyx_GetModuleGlobalName(__pyx_t_1, __pyx_n_s_sqrt); if (unlikely(!__pyx_t_1)) __PYX_ERR(2, 267, __pyx_L1_error)
   __Pyx_GOTREF(__pyx_t_1);
-  __pyx_t_6 = PyFloat_FromDouble(__pyx_v_estimatedOptimalJitterTolerance); if (unlikely(!__pyx_t_6)) __PYX_ERR(0, 273, __pyx_L1_error)
+  __pyx_t_6 = PyFloat_FromDouble(__pyx_v_estimatedOptimalJitterTolerance); if (unlikely(!__pyx_t_6)) __PYX_ERR(2, 267, __pyx_L1_error)
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@@ -8119,14 +8023,14 @@ static PyObject *__pyx_f_3fa2_7fa2util_adjustSpeedAndApplyForces(PyObject *__pyx
   __pyx_t_5 = (__pyx_t_3) ? __Pyx_PyObject_Call2Args(__pyx_t_1, __pyx_t_3, __pyx_t_6) : __Pyx_PyObject_CallOneArg(__pyx_t_1, __pyx_t_6);
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-  if (unlikely(!__pyx_t_5)) __PYX_ERR(0, 273, __pyx_L1_error)
+  if (unlikely(!__pyx_t_5)) __PYX_ERR(2, 267, __pyx_L1_error)
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-  __pyx_t_7 = __pyx_PyFloat_AsDouble(__pyx_t_5); if (unlikely((__pyx_t_7 == (double)-1) && PyErr_Occurred())) __PYX_ERR(0, 273, __pyx_L1_error)
+  __pyx_t_7 = __pyx_PyFloat_AsDouble(__pyx_t_5); if (unlikely((__pyx_t_7 == (double)-1) && PyErr_Occurred())) __PYX_ERR(2, 267, __pyx_L1_error)
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   __pyx_v_minJT = __pyx_t_7;
 
-  /* "fa2/fa2util.py":274
+  /* "fa2/fa2util.py":268
  *     estimatedOptimalJitterTolerance = .05 * sqrt(len(nodes))
  *     minJT = sqrt(estimatedOptimalJitterTolerance)
  *     maxJT = 10             # <<<<<<<<<<<<<<
@@ -8135,7 +8039,7 @@ static PyObject *__pyx_f_3fa2_7fa2util_adjustSpeedAndApplyForces(PyObject *__pyx
  */
   __pyx_v_maxJT = 10.0;
 
-  /* "fa2/fa2util.py":276
+  /* "fa2/fa2util.py":270
  *     maxJT = 10
  *     jt = jitterTolerance * max(minJT,
  *                                min(maxJT, estimatedOptimalJitterTolerance * totalEffectiveTraction / (             # <<<<<<<<<<<<<<
@@ -8144,7 +8048,7 @@ static PyObject *__pyx_f_3fa2_7fa2util_adjustSpeedAndApplyForces(PyObject *__pyx
  */
   __pyx_t_7 = (__pyx_v_estimatedOptimalJitterTolerance * __pyx_v_totalEffectiveTraction);
 
-  /* "fa2/fa2util.py":277
+  /* "fa2/fa2util.py":271
  *     jt = jitterTolerance * max(minJT,
  *                                min(maxJT, estimatedOptimalJitterTolerance * totalEffectiveTraction / (
  *                                    len(nodes) * len(nodes))))             # <<<<<<<<<<<<<<
@@ -8153,17 +8057,17 @@ static PyObject *__pyx_f_3fa2_7fa2util_adjustSpeedAndApplyForces(PyObject *__pyx
  */
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     PyErr_SetString(PyExc_TypeError, "object of type 'NoneType' has no len()");
-    __PYX_ERR(0, 277, __pyx_L1_error)
+    __PYX_ERR(2, 271, __pyx_L1_error)
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-  __pyx_t_2 = PyList_GET_SIZE(__pyx_v_nodes); if (unlikely(__pyx_t_2 == ((Py_ssize_t)-1))) __PYX_ERR(0, 277, __pyx_L1_error)
+  __pyx_t_2 = PyList_GET_SIZE(__pyx_v_nodes); if (unlikely(__pyx_t_2 == ((Py_ssize_t)-1))) __PYX_ERR(2, 271, __pyx_L1_error)
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     PyErr_SetString(PyExc_TypeError, "object of type 'NoneType' has no len()");
-    __PYX_ERR(0, 277, __pyx_L1_error)
+    __PYX_ERR(2, 271, __pyx_L1_error)
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-  __pyx_t_10 = PyList_GET_SIZE(__pyx_v_nodes); if (unlikely(__pyx_t_10 == ((Py_ssize_t)-1))) __PYX_ERR(0, 277, __pyx_L1_error)
+  __pyx_t_10 = PyList_GET_SIZE(__pyx_v_nodes); if (unlikely(__pyx_t_10 == ((Py_ssize_t)-1))) __PYX_ERR(2, 271, __pyx_L1_error)
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-  /* "fa2/fa2util.py":276
+  /* "fa2/fa2util.py":270
  *     maxJT = 10
  *     jt = jitterTolerance * max(minJT,
  *                                min(maxJT, estimatedOptimalJitterTolerance * totalEffectiveTraction / (             # <<<<<<<<<<<<<<
@@ -8172,9 +8076,9 @@ static PyObject *__pyx_f_3fa2_7fa2util_adjustSpeedAndApplyForces(PyObject *__pyx
  */
   if (unlikely(__pyx_t_11 == 0)) {
     PyErr_SetString(PyExc_ZeroDivisionError, "float division");
-    __PYX_ERR(0, 276, __pyx_L1_error)
+    __PYX_ERR(2, 270, __pyx_L1_error)
   }
-  __pyx_t_12 = (__pyx_t_7 / ((double)__pyx_t_11));
+  __pyx_t_12 = (__pyx_t_7 / __pyx_t_11);
   __pyx_t_7 = __pyx_v_maxJT;
   if (((__pyx_t_12 < __pyx_t_7) != 0)) {
     __pyx_t_13 = __pyx_t_12;
@@ -8183,7 +8087,7 @@ static PyObject *__pyx_f_3fa2_7fa2util_adjustSpeedAndApplyForces(PyObject *__pyx
   }
   __pyx_t_12 = __pyx_t_13;
 
-  /* "fa2/fa2util.py":275
+  /* "fa2/fa2util.py":269
  *     minJT = sqrt(estimatedOptimalJitterTolerance)
  *     maxJT = 10
  *     jt = jitterTolerance * max(minJT,             # <<<<<<<<<<<<<<
@@ -8192,7 +8096,7 @@ static PyObject *__pyx_f_3fa2_7fa2util_adjustSpeedAndApplyForces(PyObject *__pyx
  */
   __pyx_t_13 = __pyx_v_minJT;
 
-  /* "fa2/fa2util.py":276
+  /* "fa2/fa2util.py":270
  *     maxJT = 10
  *     jt = jitterTolerance * max(minJT,
  *                                min(maxJT, estimatedOptimalJitterTolerance * totalEffectiveTraction / (             # <<<<<<<<<<<<<<
@@ -8205,7 +8109,7 @@ static PyObject *__pyx_f_3fa2_7fa2util_adjustSpeedAndApplyForces(PyObject *__pyx
     __pyx_t_7 = __pyx_t_13;
   }
 
-  /* "fa2/fa2util.py":275
+  /* "fa2/fa2util.py":269
  *     minJT = sqrt(estimatedOptimalJitterTolerance)
  *     maxJT = 10
  *     jt = jitterTolerance * max(minJT,             # <<<<<<<<<<<<<<
@@ -8214,7 +8118,7 @@ static PyObject *__pyx_f_3fa2_7fa2util_adjustSpeedAndApplyForces(PyObject *__pyx
  */
   __pyx_v_jt = (__pyx_v_jitterTolerance * __pyx_t_7);
 
-  /* "fa2/fa2util.py":279
+  /* "fa2/fa2util.py":273
  *                                    len(nodes) * len(nodes))))
  * 
  *     minSpeedEfficiency = 0.05             # <<<<<<<<<<<<<<
@@ -8223,23 +8127,31 @@ static PyObject *__pyx_f_3fa2_7fa2util_adjustSpeedAndApplyForces(PyObject *__pyx
  */
   __pyx_v_minSpeedEfficiency = 0.05;
 
-  /* "fa2/fa2util.py":282
+  /* "fa2/fa2util.py":276
  * 
  *     # Protective against erratic behavior
- *     if totalSwinging / totalEffectiveTraction > 2.0:             # <<<<<<<<<<<<<<
+ *     if totalEffectiveTraction and totalSwinging / totalEffectiveTraction > 2.0:             # <<<<<<<<<<<<<<
  *         if speedEfficiency > minSpeedEfficiency:
  *             speedEfficiency *= .5
  */
+  __pyx_t_15 = (__pyx_v_totalEffectiveTraction != 0);
+  if (__pyx_t_15) {
+  } else {
+    __pyx_t_14 = __pyx_t_15;
+    goto __pyx_L6_bool_binop_done;
+  }
   if (unlikely(__pyx_v_totalEffectiveTraction == 0)) {
     PyErr_SetString(PyExc_ZeroDivisionError, "float division");
-    __PYX_ERR(0, 282, __pyx_L1_error)
+    __PYX_ERR(2, 276, __pyx_L1_error)
   }
-  __pyx_t_14 = (((__pyx_v_totalSwinging / __pyx_v_totalEffectiveTraction) > 2.0) != 0);
+  __pyx_t_15 = (((__pyx_v_totalSwinging / __pyx_v_totalEffectiveTraction) > 2.0) != 0);
+  __pyx_t_14 = __pyx_t_15;
+  __pyx_L6_bool_binop_done:;
   if (__pyx_t_14) {
 
-    /* "fa2/fa2util.py":283
+    /* "fa2/fa2util.py":277
  *     # Protective against erratic behavior
- *     if totalSwinging / totalEffectiveTraction > 2.0:
+ *     if totalEffectiveTraction and totalSwinging / totalEffectiveTraction > 2.0:
  *         if speedEfficiency > minSpeedEfficiency:             # <<<<<<<<<<<<<<
  *             speedEfficiency *= .5
  *         jt = max(jt, jitterTolerance)
@@ -8247,8 +8159,8 @@ static PyObject *__pyx_f_3fa2_7fa2util_adjustSpeedAndApplyForces(PyObject *__pyx
     __pyx_t_14 = ((__pyx_v_speedEfficiency > __pyx_v_minSpeedEfficiency) != 0);
     if (__pyx_t_14) {
 
-      /* "fa2/fa2util.py":284
- *     if totalSwinging / totalEffectiveTraction > 2.0:
+      /* "fa2/fa2util.py":278
+ *     if totalEffectiveTraction and totalSwinging / totalEffectiveTraction > 2.0:
  *         if speedEfficiency > minSpeedEfficiency:
  *             speedEfficiency *= .5             # <<<<<<<<<<<<<<
  *         jt = max(jt, jitterTolerance)
@@ -8256,16 +8168,16 @@ static PyObject *__pyx_f_3fa2_7fa2util_adjustSpeedAndApplyForces(PyObject *__pyx
  */
       __pyx_v_speedEfficiency = (__pyx_v_speedEfficiency * .5);
 
-      /* "fa2/fa2util.py":283
+      /* "fa2/fa2util.py":277
  *     # Protective against erratic behavior
- *     if totalSwinging / totalEffectiveTraction > 2.0:
+ *     if totalEffectiveTraction and totalSwinging / totalEffectiveTraction > 2.0:
  *         if speedEfficiency > minSpeedEfficiency:             # <<<<<<<<<<<<<<
  *             speedEfficiency *= .5
  *         jt = max(jt, jitterTolerance)
  */
     }
 
-    /* "fa2/fa2util.py":285
+    /* "fa2/fa2util.py":279
  *         if speedEfficiency > minSpeedEfficiency:
  *             speedEfficiency *= .5
  *         jt = max(jt, jitterTolerance)             # <<<<<<<<<<<<<<
@@ -8281,16 +8193,16 @@ static PyObject *__pyx_f_3fa2_7fa2util_adjustSpeedAndApplyForces(PyObject *__pyx
     }
     __pyx_v_jt = __pyx_t_13;
 
-    /* "fa2/fa2util.py":282
+    /* "fa2/fa2util.py":276
  * 
  *     # Protective against erratic behavior
- *     if totalSwinging / totalEffectiveTraction > 2.0:             # <<<<<<<<<<<<<<
+ *     if totalEffectiveTraction and totalSwinging / totalEffectiveTraction > 2.0:             # <<<<<<<<<<<<<<
  *         if speedEfficiency > minSpeedEfficiency:
  *             speedEfficiency *= .5
  */
   }
 
-  /* "fa2/fa2util.py":287
+  /* "fa2/fa2util.py":281
  *         jt = max(jt, jitterTolerance)
  * 
  *     if totalSwinging == 0:             # <<<<<<<<<<<<<<
@@ -8300,27 +8212,27 @@ static PyObject *__pyx_f_3fa2_7fa2util_adjustSpeedAndApplyForces(PyObject *__pyx
   __pyx_t_14 = ((__pyx_v_totalSwinging == 0.0) != 0);
   if (__pyx_t_14) {
 
-    /* "fa2/fa2util.py":288
+    /* "fa2/fa2util.py":282
  * 
  *     if totalSwinging == 0:
  *         targetSpeed = float('inf')             # <<<<<<<<<<<<<<
  *     else:
  *         targetSpeed = jt * speedEfficiency * totalEffectiveTraction / totalSwinging
  */
-    __pyx_t_13 = __Pyx_PyObject_AsDouble(__pyx_n_u_inf); if (unlikely(__pyx_t_13 == ((double)((double)-1)) && PyErr_Occurred())) __PYX_ERR(0, 288, __pyx_L1_error)
+    __pyx_t_13 = __Pyx_PyObject_AsDouble(__pyx_n_s_inf); if (unlikely(__pyx_t_13 == ((double)((double)-1)) && PyErr_Occurred())) __PYX_ERR(2, 282, __pyx_L1_error)
     __pyx_v_targetSpeed = __pyx_t_13;
 
-    /* "fa2/fa2util.py":287
+    /* "fa2/fa2util.py":281
  *         jt = max(jt, jitterTolerance)
  * 
  *     if totalSwinging == 0:             # <<<<<<<<<<<<<<
  *         targetSpeed = float('inf')
  *     else:
  */
-    goto __pyx_L7;
+    goto __pyx_L9;
   }
 
-  /* "fa2/fa2util.py":290
+  /* "fa2/fa2util.py":284
  *         targetSpeed = float('inf')
  *     else:
  *         targetSpeed = jt * speedEfficiency * totalEffectiveTraction / totalSwinging             # <<<<<<<<<<<<<<
@@ -8331,13 +8243,13 @@ static PyObject *__pyx_f_3fa2_7fa2util_adjustSpeedAndApplyForces(PyObject *__pyx
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     if (unlikely(__pyx_v_totalSwinging == 0)) {
       PyErr_SetString(PyExc_ZeroDivisionError, "float division");
-      __PYX_ERR(0, 290, __pyx_L1_error)
+      __PYX_ERR(2, 284, __pyx_L1_error)
     }
     __pyx_v_targetSpeed = (__pyx_t_13 / __pyx_v_totalSwinging);
   }
-  __pyx_L7:;
+  __pyx_L9:;
 
-  /* "fa2/fa2util.py":292
+  /* "fa2/fa2util.py":286
  *         targetSpeed = jt * speedEfficiency * totalEffectiveTraction / totalSwinging
  * 
  *     if totalSwinging > jt * totalEffectiveTraction:             # <<<<<<<<<<<<<<
@@ -8347,7 +8259,7 @@ static PyObject *__pyx_f_3fa2_7fa2util_adjustSpeedAndApplyForces(PyObject *__pyx
   __pyx_t_14 = ((__pyx_v_totalSwinging > (__pyx_v_jt * __pyx_v_totalEffectiveTraction)) != 0);
   if (__pyx_t_14) {
 
-    /* "fa2/fa2util.py":293
+    /* "fa2/fa2util.py":287
  * 
  *     if totalSwinging > jt * totalEffectiveTraction:
  *         if speedEfficiency > minSpeedEfficiency:             # <<<<<<<<<<<<<<
@@ -8357,7 +8269,7 @@ static PyObject *__pyx_f_3fa2_7fa2util_adjustSpeedAndApplyForces(PyObject *__pyx
     __pyx_t_14 = ((__pyx_v_speedEfficiency > __pyx_v_minSpeedEfficiency) != 0);
     if (__pyx_t_14) {
 
-      /* "fa2/fa2util.py":294
+      /* "fa2/fa2util.py":288
  *     if totalSwinging > jt * totalEffectiveTraction:
  *         if speedEfficiency > minSpeedEfficiency:
  *             speedEfficiency *= .7             # <<<<<<<<<<<<<<
@@ -8366,7 +8278,7 @@ static PyObject *__pyx_f_3fa2_7fa2util_adjustSpeedAndApplyForces(PyObject *__pyx
  */
       __pyx_v_speedEfficiency = (__pyx_v_speedEfficiency * .7);
 
-      /* "fa2/fa2util.py":293
+      /* "fa2/fa2util.py":287
  * 
  *     if totalSwinging > jt * totalEffectiveTraction:
  *         if speedEfficiency > minSpeedEfficiency:             # <<<<<<<<<<<<<<
@@ -8375,17 +8287,17 @@ static PyObject *__pyx_f_3fa2_7fa2util_adjustSpeedAndApplyForces(PyObject *__pyx
  */
     }
 
-    /* "fa2/fa2util.py":292
+    /* "fa2/fa2util.py":286
  *         targetSpeed = jt * speedEfficiency * totalEffectiveTraction / totalSwinging
  * 
  *     if totalSwinging > jt * totalEffectiveTraction:             # <<<<<<<<<<<<<<
  *         if speedEfficiency > minSpeedEfficiency:
  *             speedEfficiency *= .7
  */
-    goto __pyx_L8;
+    goto __pyx_L10;
   }
 
-  /* "fa2/fa2util.py":295
+  /* "fa2/fa2util.py":289
  *         if speedEfficiency > minSpeedEfficiency:
  *             speedEfficiency *= .7
  *     elif speed < 1000:             # <<<<<<<<<<<<<<
@@ -8395,7 +8307,7 @@ static PyObject *__pyx_f_3fa2_7fa2util_adjustSpeedAndApplyForces(PyObject *__pyx
   __pyx_t_14 = ((__pyx_v_speed < 1000.0) != 0);
   if (__pyx_t_14) {
 
-    /* "fa2/fa2util.py":296
+    /* "fa2/fa2util.py":290
  *             speedEfficiency *= .7
  *     elif speed < 1000:
  *         speedEfficiency *= 1.3             # <<<<<<<<<<<<<<
@@ -8404,7 +8316,7 @@ static PyObject *__pyx_f_3fa2_7fa2util_adjustSpeedAndApplyForces(PyObject *__pyx
  */
     __pyx_v_speedEfficiency = (__pyx_v_speedEfficiency * 1.3);
 
-    /* "fa2/fa2util.py":295
+    /* "fa2/fa2util.py":289
  *         if speedEfficiency > minSpeedEfficiency:
  *             speedEfficiency *= .7
  *     elif speed < 1000:             # <<<<<<<<<<<<<<
@@ -8412,9 +8324,9 @@ static PyObject *__pyx_f_3fa2_7fa2util_adjustSpeedAndApplyForces(PyObject *__pyx
  * 
  */
   }
-  __pyx_L8:;
+  __pyx_L10:;
 
-  /* "fa2/fa2util.py":300
+  /* "fa2/fa2util.py":294
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  *     # make the convergence drop dramatically.
  *     maxRise = .5             # <<<<<<<<<<<<<<
@@ -8423,7 +8335,7 @@ static PyObject *__pyx_f_3fa2_7fa2util_adjustSpeedAndApplyForces(PyObject *__pyx
  */
   __pyx_v_maxRise = .5;
 
-  /* "fa2/fa2util.py":301
+  /* "fa2/fa2util.py":295
  *     # make the convergence drop dramatically.
  *     maxRise = .5
  *     speed = speed + min(targetSpeed - speed, maxRise * speed)             # <<<<<<<<<<<<<<
@@ -8439,7 +8351,7 @@ static PyObject *__pyx_f_3fa2_7fa2util_adjustSpeedAndApplyForces(PyObject *__pyx
   }
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-  /* "fa2/fa2util.py":307
+  /* "fa2/fa2util.py":301
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  *     for n in nodes:             # <<<<<<<<<<<<<<
@@ -8448,33 +8360,33 @@ static PyObject *__pyx_f_3fa2_7fa2util_adjustSpeedAndApplyForces(PyObject *__pyx
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     PyErr_SetString(PyExc_TypeError, "'NoneType' object is not iterable");
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+    __pyx_t_1 = PyList_GET_ITEM(__pyx_t_5, __pyx_t_11); __Pyx_INCREF(__pyx_t_1); __pyx_t_11++; if (unlikely(0 < 0)) __PYX_ERR(2, 301, __pyx_L1_error)
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+    __pyx_t_1 = PySequence_ITEM(__pyx_t_5, __pyx_t_11); __pyx_t_11++; if (unlikely(!__pyx_t_1)) __PYX_ERR(2, 301, __pyx_L1_error)
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   __pyx_tp_dealloc_3fa2_7fa2util_Node, /*tp_dealloc*/
+  #if PY_VERSION_HEX < 0x030800b4
   0, /*tp_print*/
+  #endif
+  #if PY_VERSION_HEX >= 0x030800b4
+  0, /*tp_vectorcall_offset*/
+  #endif
   0, /*tp_getattr*/
   0, /*tp_setattr*/
   #if PY_MAJOR_VERSION < 3
@@ -10234,6 +10151,9 @@ static PyTypeObject __pyx_type_3fa2_7fa2util_Node = {
   #if PY_VERSION_HEX >= 0x030800b1
   0, /*tp_vectorcall*/
   #endif
+  #if PY_VERSION_HEX >= 0x030800b4 && PY_VERSION_HEX < 0x03090000
+  0, /*tp_print*/
+  #endif
 };
 
 static PyObject *__pyx_tp_new_3fa2_7fa2util_Edge(PyTypeObject *t, CYTHON_UNUSED PyObject *a, CYTHON_UNUSED PyObject *k) {
@@ -10317,7 +10237,12 @@ static PyTypeObject __pyx_type_3fa2_7fa2util_Edge = {
   sizeof(struct __pyx_obj_3fa2_7fa2util_Edge), /*tp_basicsize*/
   0, /*tp_itemsize*/
   __pyx_tp_dealloc_3fa2_7fa2util_Edge, /*tp_dealloc*/
+  #if PY_VERSION_HEX < 0x030800b4
   0, /*tp_print*/
+  #endif
+  #if PY_VERSION_HEX >= 0x030800b4
+  0, /*tp_vectorcall_offset*/
+  #endif
   0, /*tp_getattr*/
   0, /*tp_setattr*/
   #if PY_MAJOR_VERSION < 3
@@ -10370,6 +10295,9 @@ static PyTypeObject __pyx_type_3fa2_7fa2util_Edge = {
   #if PY_VERSION_HEX >= 0x030800b1
   0, /*tp_vectorcall*/
   #endif
+  #if PY_VERSION_HEX >= 0x030800b4 && PY_VERSION_HEX < 0x03090000
+  0, /*tp_print*/
+  #endif
 };
 static struct __pyx_vtabstruct_3fa2_7fa2util_Region __pyx_vtable_3fa2_7fa2util_Region;
 
@@ -10530,7 +10458,12 @@ static PyTypeObject __pyx_type_3fa2_7fa2util_Region = {
   sizeof(struct __pyx_obj_3fa2_7fa2util_Region), /*tp_basicsize*/
   0, /*tp_itemsize*/
   __pyx_tp_dealloc_3fa2_7fa2util_Region, /*tp_dealloc*/
+  #if PY_VERSION_HEX < 0x030800b4
   0, /*tp_print*/
+  #endif
+  #if PY_VERSION_HEX >= 0x030800b4
+  0, /*tp_vectorcall_offset*/
+  #endif
   0, /*tp_getattr*/
   0, /*tp_setattr*/
   #if PY_MAJOR_VERSION < 3
@@ -10583,6 +10516,9 @@ static PyTypeObject __pyx_type_3fa2_7fa2util_Region = {
   #if PY_VERSION_HEX >= 0x030800b1
   0, /*tp_vectorcall*/
   #endif
+  #if PY_VERSION_HEX >= 0x030800b4 && PY_VERSION_HEX < 0x03090000
+  0, /*tp_print*/
+  #endif
 };
 
 static PyMethodDef __pyx_methods[] = {
@@ -10637,7 +10573,7 @@ static __Pyx_StringTabEntry __pyx_string_tab[] = {
   {&__pyx_kp_s_Incompatible_checksums_s_vs_0x2f, __pyx_k_Incompatible_checksums_s_vs_0x2f, sizeof(__pyx_k_Incompatible_checksums_s_vs_0x2f), 0, 0, 1, 0},
   {&__pyx_kp_s_Incompatible_checksums_s_vs_0x66, __pyx_k_Incompatible_checksums_s_vs_0x66, sizeof(__pyx_k_Incompatible_checksums_s_vs_0x66), 0, 0, 1, 0},
   {&__pyx_kp_s_Incompatible_checksums_s_vs_0xb4, __pyx_k_Incompatible_checksums_s_vs_0xb4, sizeof(__pyx_k_Incompatible_checksums_s_vs_0xb4), 0, 0, 1, 0},
-  {&__pyx_kp_u_No_cython_detected_Install_cytho, __pyx_k_No_cython_detected_Install_cytho, sizeof(__pyx_k_No_cython_detected_Install_cytho), 0, 1, 0, 0},
+  {&__pyx_kp_s_No_cython_detected_Install_cytho, __pyx_k_No_cython_detected_Install_cytho, sizeof(__pyx_k_No_cython_detected_Install_cytho), 0, 0, 1, 0},
   {&__pyx_n_s_Node, __pyx_k_Node, sizeof(__pyx_k_Node), 0, 0, 1, 1},
   {&__pyx_n_s_Node___reduce_cython, __pyx_k_Node___reduce_cython, sizeof(__pyx_k_Node___reduce_cython), 0, 0, 1, 1},
   {&__pyx_n_s_Node___setstate_cython, __pyx_k_Node___setstate_cython, sizeof(__pyx_k_Node___setstate_cython), 0, 0, 1, 1},
@@ -10647,7 +10583,7 @@ static __Pyx_StringTabEntry __pyx_string_tab[] = {
   {&__pyx_n_s_Region___setstate_cython, __pyx_k_Region___setstate_cython, sizeof(__pyx_k_Region___setstate_cython), 0, 0, 1, 1},
   {&__pyx_n_s_Region_applyForceOnNodes, __pyx_k_Region_applyForceOnNodes, sizeof(__pyx_k_Region_applyForceOnNodes), 0, 0, 1, 1},
   {&__pyx_n_s_Region_buildSubRegions, __pyx_k_Region_buildSubRegions, sizeof(__pyx_k_Region_buildSubRegions), 0, 0, 1, 1},
-  {&__pyx_kp_u_Warning_uncompiled_fa2util_modul, __pyx_k_Warning_uncompiled_fa2util_modul, sizeof(__pyx_k_Warning_uncompiled_fa2util_modul), 0, 1, 0, 0},
+  {&__pyx_kp_s_Warning_uncompiled_fa2util_modul, __pyx_k_Warning_uncompiled_fa2util_modul, sizeof(__pyx_k_Warning_uncompiled_fa2util_modul), 0, 0, 1, 0},
   {&__pyx_n_s_adjustSpeedAndApplyForces, __pyx_k_adjustSpeedAndApplyForces, sizeof(__pyx_k_adjustSpeedAndApplyForces), 0, 0, 1, 1},
   {&__pyx_n_s_applyForceOnNodes, __pyx_k_applyForceOnNodes, sizeof(__pyx_k_applyForceOnNodes), 0, 0, 1, 1},
   {&__pyx_n_s_apply_attraction, __pyx_k_apply_attraction, sizeof(__pyx_k_apply_attraction), 0, 0, 1, 1},
@@ -10662,12 +10598,14 @@ static __Pyx_StringTabEntry __pyx_string_tab[] = {
   {&__pyx_n_s_e, __pyx_k_e, sizeof(__pyx_k_e), 0, 0, 1, 1},
   {&__pyx_n_s_edgeWeightInfluence, __pyx_k_edgeWeightInfluence, sizeof(__pyx_k_edgeWeightInfluence), 0, 0, 1, 1},
   {&__pyx_n_s_edges, __pyx_k_edges, sizeof(__pyx_k_edges), 0, 0, 1, 1},
+  {&__pyx_n_s_end, __pyx_k_end, sizeof(__pyx_k_end), 0, 0, 1, 1},
   {&__pyx_n_s_fa2_fa2util, __pyx_k_fa2_fa2util, sizeof(__pyx_k_fa2_fa2util), 0, 0, 1, 1},
-  {&__pyx_kp_s_fa2_fa2util_py, __pyx_k_fa2_fa2util_py, sizeof(__pyx_k_fa2_fa2util_py), 0, 0, 1, 0},
+  {&__pyx_kp_s_fa2util_py, __pyx_k_fa2util_py, sizeof(__pyx_k_fa2util_py), 0, 0, 1, 0},
+  {&__pyx_n_s_file, __pyx_k_file, sizeof(__pyx_k_file), 0, 0, 1, 1},
   {&__pyx_n_s_getstate, __pyx_k_getstate, sizeof(__pyx_k_getstate), 0, 0, 1, 1},
   {&__pyx_n_s_gravity, __pyx_k_gravity, sizeof(__pyx_k_gravity), 0, 0, 1, 1},
   {&__pyx_n_s_import, __pyx_k_import, sizeof(__pyx_k_import), 0, 0, 1, 1},
-  {&__pyx_n_u_inf, __pyx_k_inf, sizeof(__pyx_k_inf), 0, 1, 0, 1},
+  {&__pyx_n_s_inf, __pyx_k_inf, sizeof(__pyx_k_inf), 0, 0, 1, 1},
   {&__pyx_n_s_jitterTolerance, __pyx_k_jitterTolerance, sizeof(__pyx_k_jitterTolerance), 0, 0, 1, 1},
   {&__pyx_n_s_linAttraction, __pyx_k_linAttraction, sizeof(__pyx_k_linAttraction), 0, 0, 1, 1},
   {&__pyx_n_s_main, __pyx_k_main, sizeof(__pyx_k_main), 0, 0, 1, 1},
@@ -10696,9 +10634,7 @@ static __Pyx_StringTabEntry __pyx_string_tab[] = {
   {&__pyx_n_s_setstate, __pyx_k_setstate, sizeof(__pyx_k_setstate), 0, 0, 1, 1},
   {&__pyx_n_s_setstate_cython, __pyx_k_setstate_cython, sizeof(__pyx_k_setstate_cython), 0, 0, 1, 1},
   {&__pyx_n_s_speed, __pyx_k_speed, sizeof(__pyx_k_speed), 0, 0, 1, 1},
-  {&__pyx_n_u_speed, __pyx_k_speed, sizeof(__pyx_k_speed), 0, 1, 0, 1},
   {&__pyx_n_s_speedEfficiency, __pyx_k_speedEfficiency, sizeof(__pyx_k_speedEfficiency), 0, 0, 1, 1},
-  {&__pyx_n_u_speedEfficiency, __pyx_k_speedEfficiency, sizeof(__pyx_k_speedEfficiency), 0, 1, 0, 1},
   {&__pyx_n_s_sqrt, __pyx_k_sqrt, sizeof(__pyx_k_sqrt), 0, 0, 1, 1},
   {&__pyx_n_s_state, __pyx_k_state, sizeof(__pyx_k_state), 0, 0, 1, 1},
   {&__pyx_kp_s_stringsource, __pyx_k_stringsource, sizeof(__pyx_k_stringsource), 0, 0, 1, 0},
@@ -10710,10 +10646,7 @@ static __Pyx_StringTabEntry __pyx_string_tab[] = {
   {0, 0, 0, 0, 0, 0, 0}
 };
 static CYTHON_SMALL_CODE int __Pyx_InitCachedBuiltins(void) {
-  __pyx_builtin_print = __Pyx_GetBuiltinName(__pyx_n_s_print); if (!__pyx_builtin_print) __PYX_ERR(0, 324, __pyx_L1_error)
   return 0;
-  __pyx_L1_error:;
-  return -1;
 }
 
 static CYTHON_SMALL_CODE int __Pyx_InitCachedConstants(void) {
@@ -10725,10 +10658,10 @@ static CYTHON_SMALL_CODE int __Pyx_InitCachedConstants(void) {
  *     cdef tuple state
  *     cdef object _dict
  */
-  __pyx_tuple_ = PyTuple_Pack(4, __pyx_n_s_self, __pyx_n_s_state, __pyx_n_s_dict_2, __pyx_n_s_use_setstate); if (unlikely(!__pyx_tuple_)) __PYX_ERR(2, 1, __pyx_L1_error)
+  __pyx_tuple_ = PyTuple_Pack(4, __pyx_n_s_self, __pyx_n_s_state, __pyx_n_s_dict_2, __pyx_n_s_use_setstate); if (unlikely(!__pyx_tuple_)) __PYX_ERR(1, 1, __pyx_L1_error)
   __Pyx_GOTREF(__pyx_tuple_);
   __Pyx_GIVEREF(__pyx_tuple_);
-  __pyx_codeobj__2 = (PyObject*)__Pyx_PyCode_New(1, 0, 4, 0, CO_OPTIMIZED|CO_NEWLOCALS, __pyx_empty_bytes, __pyx_empty_tuple, __pyx_empty_tuple, __pyx_tuple_, __pyx_empty_tuple, __pyx_empty_tuple, __pyx_kp_s_stringsource, __pyx_n_s_reduce_cython, 1, __pyx_empty_bytes); if (unlikely(!__pyx_codeobj__2)) __PYX_ERR(2, 1, __pyx_L1_error)
+  __pyx_codeobj__2 = (PyObject*)__Pyx_PyCode_New(1, 0, 4, 0, CO_OPTIMIZED|CO_NEWLOCALS, __pyx_empty_bytes, __pyx_empty_tuple, __pyx_empty_tuple, __pyx_tuple_, __pyx_empty_tuple, __pyx_empty_tuple, __pyx_kp_s_stringsource, __pyx_n_s_reduce_cython, 1, __pyx_empty_bytes); if (unlikely(!__pyx_codeobj__2)) __PYX_ERR(1, 1, __pyx_L1_error)
 
   /* "(tree fragment)":16
  *     else:
@@ -10736,20 +10669,20 @@ static CYTHON_SMALL_CODE int __Pyx_InitCachedConstants(void) {
  * def __setstate_cython__(self, __pyx_state):             # <<<<<<<<<<<<<<
  *     __pyx_unpickle_Node__set_state(self, __pyx_state)
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-  __pyx_tuple__3 = PyTuple_Pack(2, __pyx_n_s_self, __pyx_n_s_pyx_state); if (unlikely(!__pyx_tuple__3)) __PYX_ERR(2, 16, __pyx_L1_error)
+  __pyx_tuple__3 = PyTuple_Pack(2, __pyx_n_s_self, __pyx_n_s_pyx_state); if (unlikely(!__pyx_tuple__3)) __PYX_ERR(1, 16, __pyx_L1_error)
   __Pyx_GOTREF(__pyx_tuple__3);
   __Pyx_GIVEREF(__pyx_tuple__3);
-  __pyx_codeobj__4 = (PyObject*)__Pyx_PyCode_New(2, 0, 2, 0, CO_OPTIMIZED|CO_NEWLOCALS, __pyx_empty_bytes, __pyx_empty_tuple, __pyx_empty_tuple, __pyx_tuple__3, __pyx_empty_tuple, __pyx_empty_tuple, __pyx_kp_s_stringsource, __pyx_n_s_setstate_cython, 16, __pyx_empty_bytes); if (unlikely(!__pyx_codeobj__4)) __PYX_ERR(2, 16, __pyx_L1_error)
+  __pyx_codeobj__4 = (PyObject*)__Pyx_PyCode_New(2, 0, 2, 0, CO_OPTIMIZED|CO_NEWLOCALS, __pyx_empty_bytes, __pyx_empty_tuple, __pyx_empty_tuple, __pyx_tuple__3, __pyx_empty_tuple, __pyx_empty_tuple, __pyx_kp_s_stringsource, __pyx_n_s_setstate_cython, 16, __pyx_empty_bytes); if (unlikely(!__pyx_codeobj__4)) __PYX_ERR(1, 16, __pyx_L1_error)
 
   /* "(tree fragment)":1
  * def __reduce_cython__(self):             # <<<<<<<<<<<<<<
  *     cdef tuple state
  *     cdef object _dict
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-  __pyx_tuple__5 = PyTuple_Pack(4, __pyx_n_s_self, __pyx_n_s_state, __pyx_n_s_dict_2, __pyx_n_s_use_setstate); if (unlikely(!__pyx_tuple__5)) __PYX_ERR(2, 1, __pyx_L1_error)
+  __pyx_tuple__5 = PyTuple_Pack(4, __pyx_n_s_self, __pyx_n_s_state, __pyx_n_s_dict_2, __pyx_n_s_use_setstate); if (unlikely(!__pyx_tuple__5)) __PYX_ERR(1, 1, __pyx_L1_error)
   __Pyx_GOTREF(__pyx_tuple__5);
   __Pyx_GIVEREF(__pyx_tuple__5);
-  __pyx_codeobj__6 = (PyObject*)__Pyx_PyCode_New(1, 0, 4, 0, CO_OPTIMIZED|CO_NEWLOCALS, __pyx_empty_bytes, __pyx_empty_tuple, __pyx_empty_tuple, __pyx_tuple__5, __pyx_empty_tuple, __pyx_empty_tuple, __pyx_kp_s_stringsource, __pyx_n_s_reduce_cython, 1, __pyx_empty_bytes); if (unlikely(!__pyx_codeobj__6)) __PYX_ERR(2, 1, __pyx_L1_error)
+  __pyx_codeobj__6 = (PyObject*)__Pyx_PyCode_New(1, 0, 4, 0, CO_OPTIMIZED|CO_NEWLOCALS, __pyx_empty_bytes, __pyx_empty_tuple, __pyx_empty_tuple, __pyx_tuple__5, __pyx_empty_tuple, __pyx_empty_tuple, __pyx_kp_s_stringsource, __pyx_n_s_reduce_cython, 1, __pyx_empty_bytes); if (unlikely(!__pyx_codeobj__6)) __PYX_ERR(1, 1, __pyx_L1_error)
 
   /* "(tree fragment)":16
  *     else:
@@ -10757,10 +10690,10 @@ static CYTHON_SMALL_CODE int __Pyx_InitCachedConstants(void) {
  * def __setstate_cython__(self, __pyx_state):             # <<<<<<<<<<<<<<
  *     __pyx_unpickle_Edge__set_state(self, __pyx_state)
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-  __pyx_tuple__7 = PyTuple_Pack(2, __pyx_n_s_self, __pyx_n_s_pyx_state); if (unlikely(!__pyx_tuple__7)) __PYX_ERR(2, 16, __pyx_L1_error)
+  __pyx_tuple__7 = PyTuple_Pack(2, __pyx_n_s_self, __pyx_n_s_pyx_state); if (unlikely(!__pyx_tuple__7)) __PYX_ERR(1, 16, __pyx_L1_error)
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-  __pyx_codeobj__8 = (PyObject*)__Pyx_PyCode_New(2, 0, 2, 0, CO_OPTIMIZED|CO_NEWLOCALS, __pyx_empty_bytes, __pyx_empty_tuple, __pyx_empty_tuple, __pyx_tuple__7, __pyx_empty_tuple, __pyx_empty_tuple, __pyx_kp_s_stringsource, __pyx_n_s_setstate_cython, 16, __pyx_empty_bytes); if (unlikely(!__pyx_codeobj__8)) __PYX_ERR(2, 16, __pyx_L1_error)
+  __pyx_codeobj__8 = (PyObject*)__Pyx_PyCode_New(2, 0, 2, 0, CO_OPTIMIZED|CO_NEWLOCALS, __pyx_empty_bytes, __pyx_empty_tuple, __pyx_empty_tuple, __pyx_tuple__7, __pyx_empty_tuple, __pyx_empty_tuple, __pyx_kp_s_stringsource, __pyx_n_s_setstate_cython, 16, __pyx_empty_bytes); if (unlikely(!__pyx_codeobj__8)) __PYX_ERR(1, 16, __pyx_L1_error)
 
   /* "fa2/fa2util.py":97
  * # adjust the dx and dy values of `n1` and `n2`.  It does
@@ -10769,10 +10702,10 @@ static CYTHON_SMALL_CODE int __Pyx_InitCachedConstants(void) {
  *     xDist = n1.x - n2.x
  *     yDist = n1.y - n2.y
  */
-  __pyx_tuple__9 = PyTuple_Pack(5, __pyx_n_s_n1, __pyx_n_s_n2, __pyx_n_s_e, __pyx_n_s_distributedAttraction, __pyx_n_s_coefficient); if (unlikely(!__pyx_tuple__9)) __PYX_ERR(0, 97, __pyx_L1_error)
+  __pyx_tuple__9 = PyTuple_Pack(5, __pyx_n_s_n1, __pyx_n_s_n2, __pyx_n_s_e, __pyx_n_s_distributedAttraction, __pyx_n_s_coefficient); if (unlikely(!__pyx_tuple__9)) __PYX_ERR(2, 97, __pyx_L1_error)
   __Pyx_GOTREF(__pyx_tuple__9);
   __Pyx_GIVEREF(__pyx_tuple__9);
-  __pyx_codeobj__10 = (PyObject*)__Pyx_PyCode_New(5, 0, 5, 0, CO_OPTIMIZED|CO_NEWLOCALS, __pyx_empty_bytes, __pyx_empty_tuple, __pyx_empty_tuple, __pyx_tuple__9, __pyx_empty_tuple, __pyx_empty_tuple, __pyx_kp_s_fa2_fa2util_py, __pyx_n_s_linAttraction, 97, __pyx_empty_bytes); if (unlikely(!__pyx_codeobj__10)) __PYX_ERR(0, 97, __pyx_L1_error)
+  __pyx_codeobj__10 = (PyObject*)__Pyx_PyCode_New(5, 0, 5, 0, CO_OPTIMIZED|CO_NEWLOCALS, __pyx_empty_bytes, __pyx_empty_tuple, __pyx_empty_tuple, __pyx_tuple__9, __pyx_empty_tuple, __pyx_empty_tuple, __pyx_kp_s_fa2util_py, __pyx_n_s_linAttraction, 97, __pyx_empty_bytes); if (unlikely(!__pyx_codeobj__10)) __PYX_ERR(2, 97, __pyx_L1_error)
 
   /* "fa2/fa2util.py":113
  * # the forces directly to the node objects.  These iterations are here
@@ -10781,10 +10714,10 @@ static CYTHON_SMALL_CODE int __Pyx_InitCachedConstants(void) {
  *     i = 0
  *     for n1 in nodes:
  */
-  __pyx_tuple__11 = PyTuple_Pack(2, __pyx_n_s_nodes, __pyx_n_s_coefficient); if (unlikely(!__pyx_tuple__11)) __PYX_ERR(0, 113, __pyx_L1_error)
+  __pyx_tuple__11 = PyTuple_Pack(2, __pyx_n_s_nodes, __pyx_n_s_coefficient); if (unlikely(!__pyx_tuple__11)) __PYX_ERR(2, 113, __pyx_L1_error)
   __Pyx_GOTREF(__pyx_tuple__11);
   __Pyx_GIVEREF(__pyx_tuple__11);
-  __pyx_codeobj__12 = (PyObject*)__Pyx_PyCode_New(2, 0, 2, 0, CO_OPTIMIZED|CO_NEWLOCALS, __pyx_empty_bytes, __pyx_empty_tuple, __pyx_empty_tuple, __pyx_tuple__11, __pyx_empty_tuple, __pyx_empty_tuple, __pyx_kp_s_fa2_fa2util_py, __pyx_n_s_apply_repulsion, 113, __pyx_empty_bytes); if (unlikely(!__pyx_codeobj__12)) __PYX_ERR(0, 113, __pyx_L1_error)
+  __pyx_codeobj__12 = (PyObject*)__Pyx_PyCode_New(2, 0, 2, 0, CO_OPTIMIZED|CO_NEWLOCALS, __pyx_empty_bytes, __pyx_empty_tuple, __pyx_empty_tuple, __pyx_tuple__11, __pyx_empty_tuple, __pyx_empty_tuple, __pyx_kp_s_fa2util_py, __pyx_n_s_apply_repulsion, 113, __pyx_empty_bytes); if (unlikely(!__pyx_codeobj__12)) __PYX_ERR(2, 113, __pyx_L1_error)
 
   /* "fa2/fa2util.py":125
  * 
@@ -10793,10 +10726,10 @@ static CYTHON_SMALL_CODE int __Pyx_InitCachedConstants(void) {
  *     if not useStrongGravity:
  *         for n in nodes:
  */
-  __pyx_tuple__13 = PyTuple_Pack(4, __pyx_n_s_nodes, __pyx_n_s_gravity, __pyx_n_s_scalingRatio, __pyx_n_s_useStrongGravity); if (unlikely(!__pyx_tuple__13)) __PYX_ERR(0, 125, __pyx_L1_error)
+  __pyx_tuple__13 = PyTuple_Pack(4, __pyx_n_s_nodes, __pyx_n_s_gravity, __pyx_n_s_scalingRatio, __pyx_n_s_useStrongGravity); if (unlikely(!__pyx_tuple__13)) __PYX_ERR(2, 125, __pyx_L1_error)
   __Pyx_GOTREF(__pyx_tuple__13);
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-  __pyx_codeobj__14 = (PyObject*)__Pyx_PyCode_New(4, 0, 4, 0, CO_OPTIMIZED|CO_NEWLOCALS, __pyx_empty_bytes, __pyx_empty_tuple, __pyx_empty_tuple, __pyx_tuple__13, __pyx_empty_tuple, __pyx_empty_tuple, __pyx_kp_s_fa2_fa2util_py, __pyx_n_s_apply_gravity, 125, __pyx_empty_bytes); if (unlikely(!__pyx_codeobj__14)) __PYX_ERR(0, 125, __pyx_L1_error)
+  __pyx_codeobj__14 = (PyObject*)__Pyx_PyCode_New(4, 0, 4, 0, CO_OPTIMIZED|CO_NEWLOCALS, __pyx_empty_bytes, __pyx_empty_tuple, __pyx_empty_tuple, __pyx_tuple__13, __pyx_empty_tuple, __pyx_empty_tuple, __pyx_kp_s_fa2util_py, __pyx_n_s_apply_gravity, 125, __pyx_empty_bytes); if (unlikely(!__pyx_codeobj__14)) __PYX_ERR(2, 125, __pyx_L1_error)
 
   /* "fa2/fa2util.py":134
  * 
@@ -10805,44 +10738,44 @@ static CYTHON_SMALL_CODE int __Pyx_InitCachedConstants(void) {
  *     # Optimization, since usually edgeWeightInfluence is 0 or 1, and pow is slow
  *     if edgeWeightInfluence == 0:
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-  __pyx_t_7 = __Pyx_CyFunction_NewEx(&__pyx_mdef_3fa2_7fa2util_13__pyx_unpickle_Edge, 0, __pyx_n_s_pyx_unpickle_Edge, NULL, __pyx_n_s_fa2_fa2util, __pyx_d, ((PyObject *)__pyx_codeobj__32)); if (unlikely(!__pyx_t_7)) __PYX_ERR(2, 1, __pyx_L1_error)
+  __pyx_t_7 = __Pyx_CyFunction_NewEx(&__pyx_mdef_3fa2_7fa2util_13__pyx_unpickle_Edge, 0, __pyx_n_s_pyx_unpickle_Edge, NULL, __pyx_n_s_fa2_fa2util, __pyx_d, ((PyObject *)__pyx_codeobj__30)); if (unlikely(!__pyx_t_7)) __PYX_ERR(1, 1, __pyx_L1_error)
   __Pyx_GOTREF(__pyx_t_7);
-  if (PyDict_SetItem(__pyx_d, __pyx_n_s_pyx_unpickle_Edge, __pyx_t_7) < 0) __PYX_ERR(2, 1, __pyx_L1_error)
+  if (PyDict_SetItem(__pyx_d, __pyx_n_s_pyx_unpickle_Edge, __pyx_t_7) < 0) __PYX_ERR(1, 1, __pyx_L1_error)
   __Pyx_DECREF(__pyx_t_7); __pyx_t_7 = 0;
 
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@@ -11549,9 +11457,9 @@ if (!__Pyx_RefNanny) {
  *     cdef object __pyx_PickleError
  *     cdef object __pyx_result
  */
-  __pyx_t_7 = __Pyx_CyFunction_NewEx(&__pyx_mdef_3fa2_7fa2util_15__pyx_unpickle_Region, 0, __pyx_n_s_pyx_unpickle_Region, NULL, __pyx_n_s_fa2_fa2util, __pyx_d, ((PyObject *)__pyx_codeobj__34)); if (unlikely(!__pyx_t_7)) __PYX_ERR(2, 1, __pyx_L1_error)
+  __pyx_t_7 = __Pyx_CyFunction_NewEx(&__pyx_mdef_3fa2_7fa2util_15__pyx_unpickle_Region, 0, __pyx_n_s_pyx_unpickle_Region, NULL, __pyx_n_s_fa2_fa2util, __pyx_d, ((PyObject *)__pyx_codeobj__32)); if (unlikely(!__pyx_t_7)) __PYX_ERR(1, 1, __pyx_L1_error)
   __Pyx_GOTREF(__pyx_t_7);
-  if (PyDict_SetItem(__pyx_d, __pyx_n_s_pyx_unpickle_Region, __pyx_t_7) < 0) __PYX_ERR(2, 1, __pyx_L1_error)
+  if (PyDict_SetItem(__pyx_d, __pyx_n_s_pyx_unpickle_Region, __pyx_t_7) < 0) __PYX_ERR(1, 1, __pyx_L1_error)
   __Pyx_DECREF(__pyx_t_7); __pyx_t_7 = 0;
 
   /* "fa2/fa2util.py":1
@@ -11559,9 +11467,9 @@ if (!__Pyx_RefNanny) {
  * # main code.  This allows them to be optimized with Cython.  If you
  * # don't have Cython, this will run normally.  However, if you use
  */
-  __pyx_t_7 = __Pyx_PyDict_NewPresized(0); if (unlikely(!__pyx_t_7)) __PYX_ERR(0, 1, __pyx_L1_error)
+  __pyx_t_7 = __Pyx_PyDict_NewPresized(0); if (unlikely(!__pyx_t_7)) __PYX_ERR(2, 1, __pyx_L1_error)
   __Pyx_GOTREF(__pyx_t_7);
-  if (PyDict_SetItem(__pyx_d, __pyx_n_s_test, __pyx_t_7) < 0) __PYX_ERR(0, 1, __pyx_L1_error)
+  if (PyDict_SetItem(__pyx_d, __pyx_n_s_test, __pyx_t_7) < 0) __PYX_ERR(2, 1, __pyx_L1_error)
   __Pyx_DECREF(__pyx_t_7); __pyx_t_7 = 0;
 
   /*--- Wrapped vars code ---*/
@@ -11571,7 +11479,6 @@ if (!__Pyx_RefNanny) {
   __Pyx_XDECREF(__pyx_t_1);
   __Pyx_XDECREF(__pyx_t_2);
   __Pyx_XDECREF(__pyx_t_7);
-  __Pyx_XDECREF(__pyx_t_8);
   if (__pyx_m) {
     if (__pyx_d) {
       __Pyx_AddTraceback("init fa2.fa2util", __pyx_clineno, __pyx_lineno, __pyx_filename);
@@ -11609,34 +11516,6 @@ static __Pyx_RefNannyAPIStruct *__Pyx_RefNannyImportAPI(const char *modname) {
 }
 #endif
 
-/* PyObjectGetAttrStr */
-#if CYTHON_USE_TYPE_SLOTS
-static CYTHON_INLINE PyObject* __Pyx_PyObject_GetAttrStr(PyObject* obj, PyObject* attr_name) {
-    PyTypeObject* tp = Py_TYPE(obj);
-    if (likely(tp->tp_getattro))
-        return tp->tp_getattro(obj, attr_name);
-#if PY_MAJOR_VERSION < 3
-    if (likely(tp->tp_getattr))
-        return tp->tp_getattr(obj, PyString_AS_STRING(attr_name));
-#endif
-    return PyObject_GetAttr(obj, attr_name);
-}
-#endif
-
-/* GetBuiltinName */
-static PyObject *__Pyx_GetBuiltinName(PyObject *name) {
-    PyObject* result = __Pyx_PyObject_GetAttrStr(__pyx_b, name);
-    if (unlikely(!result)) {
-        PyErr_Format(PyExc_NameError,
-#if PY_MAJOR_VERSION >= 3
-            "name '%U' is not defined", name);
-#else
-            "name '%.200s' is not defined", PyString_AS_STRING(name));
-#endif
-    }
-    return result;
-}
-
 /* RaiseArgTupleInvalid */
 static void __Pyx_RaiseArgtupleInvalid(
     const char* func_name,
@@ -11752,6 +11631,20 @@ static CYTHON_INLINE void __Pyx_ErrFetchInState(PyThreadState *tstate, PyObject
 }
 #endif
 
+/* PyObjectGetAttrStr */
+#if CYTHON_USE_TYPE_SLOTS
+static CYTHON_INLINE PyObject* __Pyx_PyObject_GetAttrStr(PyObject* obj, PyObject* attr_name) {
+    PyTypeObject* tp = Py_TYPE(obj);
+    if (likely(tp->tp_getattro))
+        return tp->tp_getattro(obj, attr_name);
+#if PY_MAJOR_VERSION < 3
+    if (likely(tp->tp_getattr))
+        return tp->tp_getattr(obj, PyString_AS_STRING(attr_name));
+#endif
+    return PyObject_GetAttr(obj, attr_name);
+}
+#endif
+
 /* GetAttr */
 static CYTHON_INLINE PyObject *__Pyx_GetAttr(PyObject *o, PyObject *n) {
 #if CYTHON_USE_TYPE_SLOTS
@@ -11780,6 +11673,20 @@ static CYTHON_INLINE PyObject *__Pyx_GetAttr3(PyObject *o, PyObject *n, PyObject
     return (likely(r)) ? r : __Pyx_GetAttr3Default(d);
 }
 
+/* GetBuiltinName */
+static PyObject *__Pyx_GetBuiltinName(PyObject *name) {
+    PyObject* result = __Pyx_PyObject_GetAttrStr(__pyx_b, name);
+    if (unlikely(!result)) {
+        PyErr_Format(PyExc_NameError,
+#if PY_MAJOR_VERSION >= 3
+            "name '%U' is not defined", name);
+#else
+            "name '%.200s' is not defined", PyString_AS_STRING(name));
+#endif
+    }
+    return result;
+}
+
 /* PyDictVersioning */
 #if CYTHON_USE_DICT_VERSIONS && CYTHON_USE_TYPE_SLOTS
 static CYTHON_INLINE PY_UINT64_T __Pyx_get_tp_dict_version(PyObject *obj) {
@@ -12843,43 +12750,43 @@ static int __Pyx_setup_reduce(PyObject* type_obj) {
     PyObject *setstate = NULL;
     PyObject *setstate_cython = NULL;
 #if CYTHON_USE_PYTYPE_LOOKUP
-    if (_PyType_Lookup((PyTypeObject*)type_obj, __pyx_n_s_getstate)) goto GOOD;
+    if (_PyType_Lookup((PyTypeObject*)type_obj, __pyx_n_s_getstate)) goto __PYX_GOOD;
 #else
-    if (PyObject_HasAttr(type_obj, __pyx_n_s_getstate)) goto GOOD;
+    if (PyObject_HasAttr(type_obj, __pyx_n_s_getstate)) goto __PYX_GOOD;
 #endif
 #if CYTHON_USE_PYTYPE_LOOKUP
-    object_reduce_ex = _PyType_Lookup(&PyBaseObject_Type, __pyx_n_s_reduce_ex); if (!object_reduce_ex) goto BAD;
+    object_reduce_ex = _PyType_Lookup(&PyBaseObject_Type, __pyx_n_s_reduce_ex); if (!object_reduce_ex) goto __PYX_BAD;
 #else
-    object_reduce_ex = __Pyx_PyObject_GetAttrStr((PyObject*)&PyBaseObject_Type, __pyx_n_s_reduce_ex); if (!object_reduce_ex) goto BAD;
+    object_reduce_ex = __Pyx_PyObject_GetAttrStr((PyObject*)&PyBaseObject_Type, __pyx_n_s_reduce_ex); if (!object_reduce_ex) goto __PYX_BAD;
 #endif
-    reduce_ex = __Pyx_PyObject_GetAttrStr(type_obj, __pyx_n_s_reduce_ex); if (unlikely(!reduce_ex)) goto BAD;
+    reduce_ex = __Pyx_PyObject_GetAttrStr(type_obj, __pyx_n_s_reduce_ex); if (unlikely(!reduce_ex)) goto __PYX_BAD;
     if (reduce_ex == object_reduce_ex) {
 #if CYTHON_USE_PYTYPE_LOOKUP
-        object_reduce = _PyType_Lookup(&PyBaseObject_Type, __pyx_n_s_reduce); if (!object_reduce) goto BAD;
+        object_reduce = _PyType_Lookup(&PyBaseObject_Type, __pyx_n_s_reduce); if (!object_reduce) goto __PYX_BAD;
 #else
-        object_reduce = __Pyx_PyObject_GetAttrStr((PyObject*)&PyBaseObject_Type, __pyx_n_s_reduce); if (!object_reduce) goto BAD;
+        object_reduce = __Pyx_PyObject_GetAttrStr((PyObject*)&PyBaseObject_Type, __pyx_n_s_reduce); if (!object_reduce) goto __PYX_BAD;
 #endif
-        reduce = __Pyx_PyObject_GetAttrStr(type_obj, __pyx_n_s_reduce); if (unlikely(!reduce)) goto BAD;
+        reduce = __Pyx_PyObject_GetAttrStr(type_obj, __pyx_n_s_reduce); if (unlikely(!reduce)) goto __PYX_BAD;
         if (reduce == object_reduce || __Pyx_setup_reduce_is_named(reduce, __pyx_n_s_reduce_cython)) {
-            reduce_cython = __Pyx_PyObject_GetAttrStr(type_obj, __pyx_n_s_reduce_cython); if (unlikely(!reduce_cython)) goto BAD;
-            ret = PyDict_SetItem(((PyTypeObject*)type_obj)->tp_dict, __pyx_n_s_reduce, reduce_cython); if (unlikely(ret < 0)) goto BAD;
-            ret = PyDict_DelItem(((PyTypeObject*)type_obj)->tp_dict, __pyx_n_s_reduce_cython); if (unlikely(ret < 0)) goto BAD;
+            reduce_cython = __Pyx_PyObject_GetAttrStr(type_obj, __pyx_n_s_reduce_cython); if (unlikely(!reduce_cython)) goto __PYX_BAD;
+            ret = PyDict_SetItem(((PyTypeObject*)type_obj)->tp_dict, __pyx_n_s_reduce, reduce_cython); if (unlikely(ret < 0)) goto __PYX_BAD;
+            ret = PyDict_DelItem(((PyTypeObject*)type_obj)->tp_dict, __pyx_n_s_reduce_cython); if (unlikely(ret < 0)) goto __PYX_BAD;
             setstate = __Pyx_PyObject_GetAttrStr(type_obj, __pyx_n_s_setstate);
             if (!setstate) PyErr_Clear();
             if (!setstate || __Pyx_setup_reduce_is_named(setstate, __pyx_n_s_setstate_cython)) {
-                setstate_cython = __Pyx_PyObject_GetAttrStr(type_obj, __pyx_n_s_setstate_cython); if (unlikely(!setstate_cython)) goto BAD;
-                ret = PyDict_SetItem(((PyTypeObject*)type_obj)->tp_dict, __pyx_n_s_setstate, setstate_cython); if (unlikely(ret < 0)) goto BAD;
-                ret = PyDict_DelItem(((PyTypeObject*)type_obj)->tp_dict, __pyx_n_s_setstate_cython); if (unlikely(ret < 0)) goto BAD;
+                setstate_cython = __Pyx_PyObject_GetAttrStr(type_obj, __pyx_n_s_setstate_cython); if (unlikely(!setstate_cython)) goto __PYX_BAD;
+                ret = PyDict_SetItem(((PyTypeObject*)type_obj)->tp_dict, __pyx_n_s_setstate, setstate_cython); if (unlikely(ret < 0)) goto __PYX_BAD;
+                ret = PyDict_DelItem(((PyTypeObject*)type_obj)->tp_dict, __pyx_n_s_setstate_cython); if (unlikely(ret < 0)) goto __PYX_BAD;
             }
             PyType_Modified((PyTypeObject*)type_obj);
         }
     }
-    goto GOOD;
-BAD:
+    goto __PYX_GOOD;
+__PYX_BAD:
     if (!PyErr_Occurred())
         PyErr_Format(PyExc_RuntimeError, "Unable to initialize pickling for %s", ((PyTypeObject*)type_obj)->tp_name);
     ret = -1;
-GOOD:
+__PYX_GOOD:
 #if !CYTHON_USE_PYTYPE_LOOKUP
     Py_XDECREF(object_reduce);
     Py_XDECREF(object_reduce_ex);
@@ -13515,6 +13422,9 @@ static PyTypeObject __pyx_CyFunctionType_type = {
 #if PY_VERSION_HEX >= 0x030800b1
     0,
 #endif
+#if PY_VERSION_HEX >= 0x030800b4 && PY_VERSION_HEX < 0x03090000
+    0,
+#endif
 };
 static int __pyx_CyFunction_init(void) {
     __pyx_CyFunctionType = __Pyx_FetchCommonType(&__pyx_CyFunctionType_type);
@@ -13938,6 +13848,112 @@ static void __Pyx_AddTraceback(const char *funcname, int c_line,
         return (target_type) value;\
     }
 
+/* Print */
+  #if !CYTHON_COMPILING_IN_PYPY && PY_MAJOR_VERSION < 3
+static PyObject *__Pyx_GetStdout(void) {
+    PyObject *f = PySys_GetObject((char *)"stdout");
+    if (!f) {
+        PyErr_SetString(PyExc_RuntimeError, "lost sys.stdout");
+    }
+    return f;
+}
+static int __Pyx_Print(PyObject* f, PyObject *arg_tuple, int newline) {
+    int i;
+    if (!f) {
+        if (!(f = __Pyx_GetStdout()))
+            return -1;
+    }
+    Py_INCREF(f);
+    for (i=0; i < PyTuple_GET_SIZE(arg_tuple); i++) {
+        PyObject* v;
+        if (PyFile_SoftSpace(f, 1)) {
+            if (PyFile_WriteString(" ", f) < 0)
+                goto error;
+        }
+        v = PyTuple_GET_ITEM(arg_tuple, i);
+        if (PyFile_WriteObject(v, f, Py_PRINT_RAW) < 0)
+            goto error;
+        if (PyString_Check(v)) {
+            char *s = PyString_AsString(v);
+            Py_ssize_t len = PyString_Size(v);
+            if (len > 0) {
+                switch (s[len-1]) {
+                    case ' ': break;
+                    case '\f': case '\r': case '\n': case '\t': case '\v':
+                        PyFile_SoftSpace(f, 0);
+                        break;
+                    default:  break;
+                }
+            }
+        }
+    }
+    if (newline) {
+        if (PyFile_WriteString("\n", f) < 0)
+            goto error;
+        PyFile_SoftSpace(f, 0);
+    }
+    Py_DECREF(f);
+    return 0;
+error:
+    Py_DECREF(f);
+    return -1;
+}
+#else
+static int __Pyx_Print(PyObject* stream, PyObject *arg_tuple, int newline) {
+    PyObject* kwargs = 0;
+    PyObject* result = 0;
+    PyObject* end_string;
+    if (unlikely(!__pyx_print)) {
+        __pyx_print = PyObject_GetAttr(__pyx_b, __pyx_n_s_print);
+        if (!__pyx_print)
+            return -1;
+    }
+    if (stream) {
+        kwargs = PyDict_New();
+        if (unlikely(!kwargs))
+            return -1;
+        if (unlikely(PyDict_SetItem(kwargs, __pyx_n_s_file, stream) < 0))
+            goto bad;
+        if (!newline) {
+            end_string = PyUnicode_FromStringAndSize(" ", 1);
+            if (unlikely(!end_string))
+                goto bad;
+            if (PyDict_SetItem(kwargs, __pyx_n_s_end, end_string) < 0) {
+                Py_DECREF(end_string);
+                goto bad;
+            }
+            Py_DECREF(end_string);
+        }
+    } else if (!newline) {
+        if (unlikely(!__pyx_print_kwargs)) {
+            __pyx_print_kwargs = PyDict_New();
+            if (unlikely(!__pyx_print_kwargs))
+                return -1;
+            end_string = PyUnicode_FromStringAndSize(" ", 1);
+            if (unlikely(!end_string))
+                return -1;
+            if (PyDict_SetItem(__pyx_print_kwargs, __pyx_n_s_end, end_string) < 0) {
+                Py_DECREF(end_string);
+                return -1;
+            }
+            Py_DECREF(end_string);
+        }
+        kwargs = __pyx_print_kwargs;
+    }
+    result = PyObject_Call(__pyx_print, arg_tuple, kwargs);
+    if (unlikely(kwargs) && (kwargs != __pyx_print_kwargs))
+        Py_DECREF(kwargs);
+    if (!result)
+        return -1;
+    Py_DECREF(result);
+    return 0;
+bad:
+    if (kwargs != __pyx_print_kwargs)
+        Py_XDECREF(kwargs);
+    return -1;
+}
+#endif
+
 /* CIntToPy */
   static CYTHON_INLINE PyObject* __Pyx_PyInt_From_long(long value) {
     const long neg_one = (long) ((long) 0 - (long) 1), const_zero = (long) 0;
@@ -14158,6 +14174,43 @@ static void __Pyx_AddTraceback(const char *funcname, int c_line,
     return (int) -1;
 }
 
+/* PrintOne */
+  #if !CYTHON_COMPILING_IN_PYPY && PY_MAJOR_VERSION < 3
+static int __Pyx_PrintOne(PyObject* f, PyObject *o) {
+    if (!f) {
+        if (!(f = __Pyx_GetStdout()))
+            return -1;
+    }
+    Py_INCREF(f);
+    if (PyFile_SoftSpace(f, 0)) {
+        if (PyFile_WriteString(" ", f) < 0)
+            goto error;
+    }
+    if (PyFile_WriteObject(o, f, Py_PRINT_RAW) < 0)
+        goto error;
+    if (PyFile_WriteString("\n", f) < 0)
+        goto error;
+    Py_DECREF(f);
+    return 0;
+error:
+    Py_DECREF(f);
+    return -1;
+    /* the line below is just to avoid C compiler
+     * warnings about unused functions */
+    return __Pyx_Print(f, NULL, 0);
+}
+#else
+static int __Pyx_PrintOne(PyObject* stream, PyObject *o) {
+    int res;
+    PyObject* arg_tuple = PyTuple_Pack(1, o);
+    if (unlikely(!arg_tuple))
+        return -1;
+    res = __Pyx_Print(stream, arg_tuple, 1);
+    Py_DECREF(arg_tuple);
+    return res;
+}
+#endif
+
 /* CIntFromPy */
   static CYTHON_INLINE long __Pyx_PyInt_As_long(PyObject *x) {
     const long neg_one = (long) ((long) 0 - (long) 1), const_zero = (long) 0;
diff --git a/fa2/fa2util.pxd b/fa2/fa2util.pxd
index adaf628..ff43384 100644
--- a/fa2/fa2util.pxd
+++ b/fa2/fa2util.pxd
@@ -87,8 +87,6 @@ cdef class Region:
     cdef void updateMassAndGeometry(self)
 
     @cython.locals(n = Node,
-                   leftNodes = list,
-                   rightNodes = list,
                    topleftNodes = list,
                    bottomleftNodes = list,
                    toprightNodes = list,
diff --git a/fa2/fa2util.py b/fa2/fa2util.py
index 0fcfeae..a1fadfc 100644
--- a/fa2/fa2util.py
+++ b/fa2/fa2util.py
@@ -175,30 +175,24 @@ def updateMassAndGeometry(self):
 
     def buildSubRegions(self):
         if len(self.nodes) > 1:
-
-            leftNodes = []
-            rightNodes = []
-            for n in self.nodes:
-                if n.x < self.massCenterX:
-                    leftNodes.append(n)
-                else:
-                    rightNodes.append(n)
-
             topleftNodes = []
             bottomleftNodes = []
-            for n in leftNodes:
-                if n.y < self.massCenterY:
-                    topleftNodes.append(n)
-                else:
-                    bottomleftNodes.append(n)
-
             toprightNodes = []
             bottomrightNodes = []
-            for n in rightNodes:
-                if n.y < self.massCenterY:
-                    toprightNodes.append(n)
+            # Optimization: The distribution of self.nodes into 
+            # subregions now requires only one for loop. Removed 
+            # topNodes and bottomNodes arrays: memory space saving.
+            for n in self.nodes:
+                if n.x < self.massCenterX:
+                    if n.y < self.massCenterY:
+                        bottomleftNodes.append(n)
+                    else:
+                        topleftNodes.append(n)
                 else:
-                    bottomrightNodes.append(n)
+                    if n.y < self.massCenterY:
+                        bottomrightNodes.append(n)
+                    else:
+                        toprightNodes.append(n)      
 
             if len(topleftNodes) > 0:
                 if len(topleftNodes) < len(self.nodes):