X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=src%2FCube.hs;h=11762a5efeb0b1366d0455da5e97198f82ece0fc;hb=71c69c67074e6eb6ce7520739bc729691525b20b;hp=26b513d5983d0f5784375c29246a980db450b9fb;hpb=1fbb737e99c620f9ca3acd7d8a455ae57ca45130;p=spline3.git

diff --git a/src/Cube.hs b/src/Cube.hs
index 26b513d..11762a5 100644
--- a/src/Cube.hs
+++ b/src/Cube.hs
@@ -25,26 +25,18 @@ import Test.QuickCheck (Arbitrary(..), Gen, Positive(..), choose)
 import Cardinal
 import Comparisons ((~=), (~~=))
 import qualified Face (Face(Face, v0, v1, v2, v3))
-import FunctionValues
+import FunctionValues (FunctionValues, eval, rotate)
 import Misc (all_equal, disjoint)
-import Point
-import Tetrahedron (
-  Tetrahedron(..),
-  c,
-  b0,
-  b1,
-  b2,
-  b3,
-  volume
-  )
+import Point (Point(..), dot)
+import Tetrahedron (Tetrahedron(..), c, volume)
 import ThreeDimensional
 
-data Cube = Cube { h :: Double,
-                   i :: Int,
-                   j :: Int,
-                   k :: Int,
-                   fv :: FunctionValues,
-                   tetrahedra_volume :: Double }
+data Cube = Cube { h  :: !Double,
+                   i  :: !Int,
+                   j  :: !Int,
+                   k  :: !Int,
+                   fv :: !FunctionValues,
+                   tetrahedra_volume :: !Double }
             deriving (Eq)
 
 
@@ -57,9 +49,13 @@ instance Arbitrary Cube where
       fv' <- arbitrary :: Gen FunctionValues
       (Positive tet_vol) <- arbitrary :: Gen (Positive Double)
       return (Cube h' i' j' k' fv' tet_vol)
-        where
-          coordmin = -268435456 -- -(2^29 / 2)
-          coordmax = 268435456  -- +(2^29 / 2)
+      where
+        -- The idea here is that, when cubed in the volume formula,
+        -- these numbers don't overflow 64 bits. This number is not
+        -- magic in any other sense than that it does not cause test
+        -- failures, while 2^23 does.
+        coordmax = 4194304 -- 2^22
+        coordmin = -coordmax
 
 
 instance Show Cube where
@@ -72,8 +68,7 @@ instance Show Cube where
         " ymin: " ++ (show (ymin cube)) ++ "\n" ++
         " ymax: " ++ (show (ymax cube)) ++ "\n" ++
         " zmin: " ++ (show (zmin cube)) ++ "\n" ++
-        " zmax: " ++ (show (zmax cube)) ++ "\n" ++
-        " fv: " ++ (show (Cube.fv cube)) ++ "\n"
+        " zmax: " ++ (show (zmax cube)) ++ "\n"
         where
           subscript =
               (show (i cube)) ++ "," ++ (show (j cube)) ++ "," ++ (show (k cube))
@@ -82,7 +77,7 @@ instance Show Cube where
 -- | The left-side boundary of the cube. See Sorokina and Zeilfelder,
 --   p. 76.
 xmin :: Cube -> Double
-xmin cube = (2*i' - 1)*delta / 2
+xmin cube = (i' - 1/2)*delta
     where
       i' = fromIntegral (i cube) :: Double
       delta = h cube
@@ -90,7 +85,7 @@ xmin cube = (2*i' - 1)*delta / 2
 -- | The right-side boundary of the cube. See Sorokina and Zeilfelder,
 --   p. 76.
 xmax :: Cube -> Double
-xmax cube = (2*i' + 1)*delta / 2
+xmax cube = (i' + 1/2)*delta
     where
       i' = fromIntegral (i cube) :: Double
       delta = h cube
@@ -98,7 +93,7 @@ xmax cube = (2*i' + 1)*delta / 2
 -- | The front boundary of the cube. See Sorokina and Zeilfelder,
 --   p. 76.
 ymin :: Cube -> Double
-ymin cube = (2*j' - 1)*delta / 2
+ymin cube = (j' - 1/2)*delta
     where
       j' = fromIntegral (j cube) :: Double
       delta = h cube
@@ -106,7 +101,7 @@ ymin cube = (2*j' - 1)*delta / 2
 -- | The back boundary of the cube. See Sorokina and Zeilfelder,
 --   p. 76.
 ymax :: Cube -> Double
-ymax cube = (2*j' + 1)*delta / 2
+ymax cube = (j' + 1/2)*delta
     where
       j' = fromIntegral (j cube) :: Double
       delta = h cube
@@ -114,7 +109,7 @@ ymax cube = (2*j' + 1)*delta / 2
 -- | The bottom boundary of the cube. See Sorokina and Zeilfelder,
 --   p. 76.
 zmin :: Cube -> Double
-zmin cube = (2*k' - 1)*delta / 2
+zmin cube = (k' - 1/2)*delta
     where
       k' = fromIntegral (k cube) :: Double
       delta = h cube
@@ -122,7 +117,7 @@ zmin cube = (2*k' - 1)*delta / 2
 -- | The top boundary of the cube. See Sorokina and Zeilfelder,
 --   p. 76.
 zmax :: Cube -> Double
-zmax cube = (2*k' + 1)*delta / 2
+zmax cube = (k' + 1/2)*delta
     where
       k' = fromIntegral (k cube) :: Double
       delta = h cube
@@ -130,7 +125,7 @@ zmax cube = (2*k' + 1)*delta / 2
 instance ThreeDimensional Cube where
     -- | The center of Cube_ijk coincides with v_ijk at
     --   (ih, jh, kh). See Sorokina and Zeilfelder, p. 76.
-    center cube = (x, y, z)
+    center cube = Point x y z
            where
              delta = h cube
              i' = fromIntegral (i cube) :: Double
@@ -142,7 +137,7 @@ instance ThreeDimensional Cube where
 
     -- | It's easy to tell if a point is within a cube; just make sure
     --   that it falls on the proper side of each of the cube's faces.
-    contains_point cube (x, y, z)
+    contains_point cube (Point x y z)
         | x < (xmin cube) = False
         | x > (xmax cube) = False
         | y < (ymin cube) = False
@@ -160,10 +155,11 @@ top_face :: Cube -> Face.Face
 top_face cube = Face.Face v0' v1' v2' v3'
     where
       delta = (1/2)*(h cube)
-      v0' = (center cube) + (delta, -delta, delta)
-      v1' = (center cube) + (delta, delta, delta)
-      v2' = (center cube) + (-delta, delta, delta)
-      v3' = (center cube) + (-delta, -delta, delta)
+      cc  = center cube
+      v0' = cc + ( Point delta (-delta) delta )
+      v1' = cc + ( Point delta delta delta )
+      v2' = cc + ( Point (-delta) delta delta )
+      v3' = cc + ( Point (-delta) (-delta) delta )
 
 
 
@@ -172,10 +168,11 @@ back_face :: Cube -> Face.Face
 back_face cube = Face.Face v0' v1' v2' v3'
     where
       delta = (1/2)*(h cube)
-      v0' = (center cube) + (delta, -delta, -delta)
-      v1' = (center cube) + (delta, delta, -delta)
-      v2' = (center cube) + (delta, delta, delta)
-      v3' = (center cube) + (delta, -delta, delta)
+      cc  = center cube
+      v0' = cc + ( Point delta (-delta) (-delta) )
+      v1' = cc + ( Point delta delta (-delta) )
+      v2' = cc + ( Point delta delta delta )
+      v3' = cc + ( Point delta (-delta) delta )
 
 
 -- The bottom face (in the direction of -z) of the cube.
@@ -183,10 +180,11 @@ down_face :: Cube -> Face.Face
 down_face cube = Face.Face v0' v1' v2' v3'
     where
       delta = (1/2)*(h cube)
-      v0' = (center cube) + (-delta, -delta, -delta)
-      v1' = (center cube) + (-delta, delta, -delta)
-      v2' = (center cube) + (delta, delta, -delta)
-      v3' = (center cube) + (delta, -delta, -delta)
+      cc  = center cube
+      v0' = cc + ( Point (-delta) (-delta) (-delta) )
+      v1' = cc + ( Point (-delta) delta (-delta) )
+      v2' = cc + ( Point delta delta (-delta) )
+      v3' = cc + ( Point delta (-delta) (-delta) )
 
 
 
@@ -195,20 +193,22 @@ front_face :: Cube -> Face.Face
 front_face cube = Face.Face v0' v1' v2' v3'
     where
       delta = (1/2)*(h cube)
-      v0' = (center cube) + (-delta, -delta, delta)
-      v1' = (center cube) + (-delta, delta, delta)
-      v2' = (center cube) + (-delta, delta, -delta)
-      v3' = (center cube) + (-delta, -delta, -delta)
+      cc  = center cube
+      v0' = cc + ( Point (-delta) (-delta) delta )
+      v1' = cc + ( Point (-delta) delta delta )
+      v2' = cc + ( Point (-delta) delta (-delta) )
+      v3' = cc + ( Point (-delta) (-delta) (-delta) )
 
 -- | The left (in the direction of -y) face of the cube.
 left_face :: Cube -> Face.Face
 left_face cube = Face.Face v0' v1' v2' v3'
     where
       delta = (1/2)*(h cube)
-      v0' = (center cube) + (delta, -delta, delta)
-      v1' = (center cube) + (-delta, -delta, delta)
-      v2' = (center cube) + (-delta, -delta, -delta)
-      v3' = (center cube) + (delta, -delta, -delta)
+      cc  = center cube
+      v0' = cc + ( Point delta (-delta) delta )
+      v1' = cc + ( Point (-delta) (-delta) delta )
+      v2' = cc + ( Point (-delta) (-delta) (-delta) )
+      v3' = cc + ( Point delta (-delta) (-delta) )
 
 
 -- | The right (in the direction of y) face of the cube.
@@ -216,10 +216,11 @@ right_face :: Cube -> Face.Face
 right_face cube = Face.Face v0' v1' v2' v3'
     where
       delta = (1/2)*(h cube)
-      v0' = (center cube) + (-delta, delta, delta)
-      v1' = (center cube) + (delta, delta, delta)
-      v2' = (center cube) + (delta, delta, -delta)
-      v3' = (center cube) + (-delta, delta, -delta)
+      cc  = center cube
+      v0' = cc + ( Point (-delta) delta delta)
+      v1' = cc + ( Point delta  delta delta )
+      v2' = cc + ( Point delta delta (-delta) )
+      v3' = cc + ( Point (-delta) delta (-delta) )
 
 
 tetrahedron :: Cube -> Int -> Tetrahedron
@@ -228,18 +229,20 @@ tetrahedron cube 0 =
     Tetrahedron (fv cube) v0' v1' v2' v3' vol
     where
       v0' = center cube
-      v1' = center (front_face cube)
-      v2' = Face.v0 (front_face cube)
-      v3' = Face.v1 (front_face cube)
+      ff  = front_face cube
+      v1' = center ff
+      v2' = Face.v0 ff
+      v3' = Face.v1 ff
       vol = tetrahedra_volume cube
 
 tetrahedron cube 1 =
     Tetrahedron fv' v0' v1' v2' v3' vol
     where
       v0' = center cube
-      v1' = center (front_face cube)
-      v2' = Face.v1 (front_face cube)
-      v3' = Face.v2 (front_face cube)
+      ff  = front_face cube
+      v1' = center ff
+      v2' = Face.v1 ff
+      v3' = Face.v2 ff
       fv' = rotate ccwx (fv cube)
       vol = tetrahedra_volume cube
 
@@ -247,9 +250,10 @@ tetrahedron cube 2 =
     Tetrahedron fv' v0' v1' v2' v3' vol
     where
       v0' = center cube
-      v1' = center (front_face cube)
-      v2' = Face.v2 (front_face cube)
-      v3' = Face.v3 (front_face cube)
+      ff  = front_face cube
+      v1' = center ff
+      v2' = Face.v2 ff
+      v3' = Face.v3 ff
       fv' = rotate ccwx $ rotate ccwx $ fv cube
       vol = tetrahedra_volume cube
 
@@ -257,9 +261,10 @@ tetrahedron cube 3 =
     Tetrahedron fv' v0' v1' v2' v3' vol
     where
       v0' = center cube
-      v1' = center (front_face cube)
-      v2' = Face.v3 (front_face cube)
-      v3' = Face.v0 (front_face cube)
+      ff  = front_face cube
+      v1' = center ff
+      v2' = Face.v3 ff
+      v3' = Face.v0 ff
       fv' = rotate cwx (fv cube)
       vol = tetrahedra_volume cube
 
@@ -267,9 +272,10 @@ tetrahedron cube 4 =
     Tetrahedron fv' v0' v1' v2' v3' vol
     where
       v0' = center cube
-      v1' = center (top_face cube)
-      v2' = Face.v0 (top_face cube)
-      v3' = Face.v1 (top_face cube)
+      tf  = top_face cube
+      v1' = center tf
+      v2' = Face.v0 tf
+      v3' = Face.v1 tf
       fv' = rotate cwy (fv cube)
       vol = tetrahedra_volume cube
 
@@ -277,9 +283,10 @@ tetrahedron cube 5 =
     Tetrahedron fv' v0' v1' v2' v3' vol
     where
       v0' = center cube
-      v1' = center (top_face cube)
-      v2' = Face.v1 (top_face cube)
-      v3' = Face.v2 (top_face cube)
+      tf  = top_face cube
+      v1' = center tf
+      v2' = Face.v1 tf
+      v3' = Face.v2 tf
       fv' = rotate cwy $ rotate cwz $ fv cube
       vol = tetrahedra_volume cube
 
@@ -287,9 +294,10 @@ tetrahedron cube 6 =
     Tetrahedron fv' v0' v1' v2' v3' vol
     where
       v0' = center cube
-      v1' = center (top_face cube)
-      v2' = Face.v2 (top_face cube)
-      v3' = Face.v3 (top_face cube)
+      tf  = top_face cube
+      v1' = center tf
+      v2' = Face.v2 tf
+      v3' = Face.v3 tf
       fv' = rotate cwy $ rotate cwz
                        $ rotate cwz
                        $ fv cube
@@ -299,9 +307,10 @@ tetrahedron cube 7 =
     Tetrahedron fv' v0' v1' v2' v3' vol
     where
       v0' = center cube
-      v1' = center (top_face cube)
-      v2' = Face.v3 (top_face cube)
-      v3' = Face.v0 (top_face cube)
+      tf  = top_face cube
+      v1' = center tf
+      v2' = Face.v3 tf
+      v3' = Face.v0 tf
       fv' = rotate cwy $ rotate ccwz $ fv cube
       vol = tetrahedra_volume cube
 
@@ -309,9 +318,10 @@ tetrahedron cube 8 =
     Tetrahedron fv' v0' v1' v2' v3' vol
     where
       v0' = center cube
-      v1' = center (back_face cube)
-      v2' = Face.v0 (back_face cube)
-      v3' = Face.v1 (back_face cube)
+      bf  = back_face cube
+      v1' = center bf
+      v2' = Face.v0 bf
+      v3' = Face.v1 bf
       fv' = rotate cwy $ rotate cwy $ fv cube
       vol = tetrahedra_volume cube
 
@@ -319,9 +329,10 @@ tetrahedron cube 9 =
     Tetrahedron fv' v0' v1' v2' v3' vol
     where
       v0' = center cube
-      v1' = center (back_face cube)
-      v2' = Face.v1 (back_face cube)
-      v3' = Face.v2 (back_face cube)
+      bf  = back_face cube
+      v1' = center bf
+      v2' = Face.v1 bf
+      v3' = Face.v2 bf
       fv' = rotate cwy $ rotate cwy
                        $ rotate cwx
                        $ fv cube
@@ -331,9 +342,10 @@ tetrahedron cube 10 =
     Tetrahedron fv' v0' v1' v2' v3' vol
     where
       v0' = center cube
-      v1' = center (back_face cube)
-      v2' = Face.v2 (back_face cube)
-      v3' = Face.v3 (back_face cube)
+      bf  = back_face cube
+      v1' = center bf
+      v2' = Face.v2 bf
+      v3' = Face.v3 bf
       fv' = rotate cwy $ rotate cwy
                        $ rotate cwx
                        $ rotate cwx
@@ -345,9 +357,10 @@ tetrahedron cube 11 =
     Tetrahedron fv' v0' v1' v2' v3' vol
     where
       v0' = center cube
-      v1' = center (back_face cube)
-      v2' = Face.v3 (back_face cube)
-      v3' = Face.v0 (back_face cube)
+      bf  = back_face cube
+      v1' = center bf
+      v2' = Face.v3 bf
+      v3' = Face.v0 bf
       fv' = rotate cwy $ rotate cwy
                        $ rotate ccwx
                        $ fv cube
@@ -357,9 +370,10 @@ tetrahedron cube 12 =
     Tetrahedron fv' v0' v1' v2' v3' vol
     where
       v0' = center cube
-      v1' = center (down_face cube)
-      v2' = Face.v0 (down_face cube)
-      v3' = Face.v1 (down_face cube)
+      df  = down_face cube
+      v1' = center df
+      v2' = Face.v0 df
+      v3' = Face.v1 df
       fv' = rotate ccwy $ fv cube
       vol = tetrahedra_volume cube
 
@@ -367,9 +381,10 @@ tetrahedron cube 13 =
     Tetrahedron fv' v0' v1' v2' v3' vol
     where
       v0' = center cube
-      v1' = center (down_face cube)
-      v2' = Face.v1 (down_face cube)
-      v3' = Face.v2 (down_face cube)
+      df  = down_face cube
+      v1' = center df
+      v2' = Face.v1 df
+      v3' = Face.v2 df
       fv' = rotate ccwy $ rotate ccwz $ fv cube
       vol = tetrahedra_volume cube
 
@@ -377,9 +392,10 @@ tetrahedron cube 14 =
     Tetrahedron fv' v0' v1' v2' v3' vol
     where
       v0' = center cube
-      v1' = center (down_face cube)
-      v2' = Face.v2 (down_face cube)
-      v3' = Face.v3 (down_face cube)
+      df  = down_face cube
+      v1' = center df
+      v2' = Face.v2 df
+      v3' = Face.v3 df
       fv' = rotate ccwy $ rotate ccwz
                         $ rotate ccwz
                         $ fv cube
@@ -389,9 +405,10 @@ tetrahedron cube 15 =
     Tetrahedron fv' v0' v1' v2' v3' vol
     where
       v0' = center cube
-      v1' = center (down_face cube)
-      v2' = Face.v3 (down_face cube)
-      v3' = Face.v0 (down_face cube)
+      df  = down_face cube
+      v1' = center df
+      v2' = Face.v3 df
+      v3' = Face.v0 df
       fv' = rotate ccwy $ rotate cwz $ fv cube
       vol = tetrahedra_volume cube
 
@@ -399,9 +416,10 @@ tetrahedron cube 16 =
     Tetrahedron fv' v0' v1' v2' v3' vol
     where
       v0' = center cube
-      v1' = center (right_face cube)
-      v2' = Face.v0 (right_face cube)
-      v3' = Face.v1 (right_face cube)
+      rf  = right_face cube
+      v1' = center rf
+      v2' = Face.v0 rf
+      v3' = Face.v1 rf
       fv' = rotate ccwz $ fv cube
       vol = tetrahedra_volume cube
 
@@ -409,9 +427,10 @@ tetrahedron cube 17 =
     Tetrahedron fv' v0' v1' v2' v3' vol
     where
       v0' = center cube
-      v1' = center (right_face cube)
-      v2' = Face.v1 (right_face cube)
-      v3' = Face.v2 (right_face cube)
+      rf  = right_face cube
+      v1' = center rf
+      v2' = Face.v1 rf
+      v3' = Face.v2 rf
       fv' = rotate ccwz $ rotate cwy $ fv cube
       vol = tetrahedra_volume cube
 
@@ -419,9 +438,10 @@ tetrahedron cube 18 =
     Tetrahedron fv' v0' v1' v2' v3' vol
     where
       v0' = center cube
-      v1' = center (right_face cube)
-      v2' = Face.v2 (right_face cube)
-      v3' = Face.v3 (right_face cube)
+      rf  = right_face cube
+      v1' = center rf
+      v2' = Face.v2 rf
+      v3' = Face.v3 rf
       fv' = rotate ccwz $ rotate cwy
                         $ rotate cwy
                         $ fv cube
@@ -431,9 +451,10 @@ tetrahedron cube 19 =
     Tetrahedron fv' v0' v1' v2' v3' vol
     where
       v0' = center cube
-      v1' = center (right_face cube)
-      v2' = Face.v3 (right_face cube)
-      v3' = Face.v0 (right_face cube)
+      rf  = right_face cube
+      v1' = center rf
+      v2' = Face.v3 rf
+      v3' = Face.v0 rf
       fv' = rotate ccwz $ rotate ccwy
                         $ fv cube
       vol = tetrahedra_volume cube
@@ -442,9 +463,10 @@ tetrahedron cube 20 =
     Tetrahedron fv' v0' v1' v2' v3' vol
     where
       v0' = center cube
-      v1' = center (left_face cube)
-      v2' = Face.v0 (left_face cube)
-      v3' = Face.v1 (left_face cube)
+      lf  = left_face cube
+      v1' = center lf
+      v2' = Face.v0 lf
+      v3' = Face.v1 lf
       fv' = rotate cwz $ fv cube
       vol = tetrahedra_volume cube
 
@@ -452,9 +474,10 @@ tetrahedron cube 21 =
     Tetrahedron fv' v0' v1' v2' v3' vol
     where
       v0' = center cube
-      v1' = center (left_face cube)
-      v2' = Face.v1 (left_face cube)
-      v3' = Face.v2 (left_face cube)
+      lf  = left_face cube
+      v1' = center lf
+      v2' = Face.v1 lf
+      v3' = Face.v2 lf
       fv' = rotate cwz $ rotate ccwy $ fv cube
       vol = tetrahedra_volume cube
 
@@ -462,9 +485,10 @@ tetrahedron cube 22 =
     Tetrahedron fv' v0' v1' v2' v3' vol
     where
       v0' = center cube
-      v1' = center (left_face cube)
-      v2' = Face.v2 (left_face cube)
-      v3' = Face.v3 (left_face cube)
+      lf  = left_face cube
+      v1' = center lf
+      v2' = Face.v2 lf
+      v3' = Face.v3 lf
       fv' = rotate cwz $ rotate ccwy
                        $ rotate ccwy
                        $ fv cube
@@ -474,9 +498,10 @@ tetrahedron cube 23 =
     Tetrahedron fv' v0' v1' v2' v3' vol
     where
       v0' = center cube
-      v1' = center (left_face cube)
-      v2' = Face.v3 (left_face cube)
-      v3' = Face.v0 (left_face cube)
+      lf  = left_face cube
+      v1' = center lf
+      v2' = Face.v3 lf
+      v3' = Face.v0 lf
       fv' = rotate cwz $ rotate cwy
                        $ fv cube
       vol = tetrahedra_volume cube
@@ -563,14 +588,14 @@ back_right_down_tetrahedra  cube =
     (tetrahedron cube 18)
 
 in_top_half :: Cube -> Point -> Bool
-in_top_half cube (_,_,z) =
+in_top_half cube (Point _ _ z) =
   distance_from_top <= distance_from_bottom
   where
     distance_from_top = abs $ (zmax cube) - z
     distance_from_bottom = abs $ (zmin cube) - z
 
 in_front_half :: Cube -> Point -> Bool
-in_front_half cube (x,_,_) =
+in_front_half cube (Point x _ _) =
     distance_from_front <= distance_from_back
   where
     distance_from_front = abs $ (xmin cube) - x
@@ -578,7 +603,7 @@ in_front_half cube (x,_,_) =
 
 
 in_left_half :: Cube -> Point -> Bool
-in_left_half cube (_,y,_) =
+in_left_half cube (Point _ y _) =
     distance_from_left <= distance_from_right
   where
     distance_from_left = abs $ (ymin cube) - y
@@ -595,6 +620,7 @@ in_left_half cube (_,y,_) =
 --   This can throw an exception, but the use of 'head' might
 --   save us some unnecessary computations.
 --
+{-# INLINE find_containing_tetrahedron #-}
 find_containing_tetrahedron :: Cube -> Point -> Tetrahedron
 find_containing_tetrahedron cube p =
   candidates `V.unsafeIndex` (fromJust lucky_idx)
@@ -630,8 +656,9 @@ find_containing_tetrahedron cube p =
           else
             back_right_down_tetrahedra cube
 
-    -- Use the dot product instead of 'distance' here to save a
-    -- sqrt(). So, "distances" below really means "distances squared."
+    -- Use the dot product instead of Euclidean distance here to save
+    -- a sqrt(). So, "distances" below really means "distances
+    -- squared."
     distances = V.map ((dot p) . center) candidates
     shortest_distance = V.minimum distances
     lucky_idx = V.findIndex
@@ -673,15 +700,15 @@ prop_opposite_octant_tetrahedra_disjoint6 cube =
 
 
 -- | Since the grid size is necessarily positive, all tetrahedra
---   (which comprise cubes of positive volume) must have positive volume
---   as well.
+--   (which comprise cubes of positive volume) must have positive
+--   volume as well.
 prop_all_volumes_positive :: Cube -> Bool
 prop_all_volumes_positive cube =
-    null nonpositive_volumes
+    all (>= 0) volumes
     where
       ts = tetrahedra cube
       volumes = map volume ts
-      nonpositive_volumes = filter (<= 0) volumes
+
 
 -- | In fact, since all of the tetrahedra are identical, we should
 --   already know their volumes. There's 24 tetrahedra to a cube, so
@@ -955,23 +982,6 @@ prop_c1011_identity cube =
         t6 = tetrahedron cube 6
 
 
-
--- | Given in Sorokina and Zeilfelder, p. 78.
-prop_cijk1_identity :: Cube -> Bool
-prop_cijk1_identity cube =
-     and [ c t0 i j k 1 ~=
-                 (c t1 (i+1) j k 0) * ((b0 t0) (v3 t1)) +
-                 (c t1 i (j+1) k 0) * ((b1 t0) (v3 t1)) +
-                 (c t1 i j (k+1) 0) * ((b2 t0) (v3 t1)) +
-                 (c t1 i j k 1) * ((b3 t0) (v3 t1)) | i <- [0..2],
-                                                      j <- [0..2],
-                                                      k <- [0..2],
-                                                      i + j + k == 2]
-      where
-        t0 = tetrahedron cube 0
-        t1 = tetrahedron cube 1
-
-
 -- | The function values at the interior should be the same for all
 --   tetrahedra.
 prop_interior_values_all_identical :: Cube -> Bool
@@ -1139,14 +1149,6 @@ prop_t7_shares_edge_with_t20 cube =
         t20 = tetrahedron cube 20
 
 
-
-
-
-p78_25_properties :: Test.Framework.Test
-p78_25_properties =
-    testGroup "p. 78, Section (2.5) Properties" [
-      testProperty "c_ijk1 identity" prop_cijk1_identity ]
-
 p79_26_properties :: Test.Framework.Test
 p79_26_properties =
     testGroup "p. 79, Section (2.6) Properties" [
@@ -1207,7 +1209,6 @@ edge_incidence_tests =
 cube_properties :: Test.Framework.Test
 cube_properties =
   testGroup "Cube Properties" [
-    p78_25_properties,
     p79_26_properties,
     p79_27_properties,
     p79_28_properties,