From b18e13462e37fd48e1d19d131a41e3743252ae31 Mon Sep 17 00:00:00 2001
From: Michael Orlitzky <michael@orlitzky.com>
Date: Fri, 2 Sep 2011 12:58:40 -0400
Subject: [PATCH] Only compute 'cubes' once, and store it in a new Grid field,
 cube_grid.

---
 src/Grid.hs | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/src/Grid.hs b/src/Grid.hs
index d87114f..ba8ca20 100644
--- a/src/Grid.hs
+++ b/src/Grid.hs
@@ -24,7 +24,8 @@ type CubeGrid = Array (Int,Int,Int) Cube
 --   function at the grid points, which are distance h from one
 --   another in each direction (x,y,z).
 data Grid = Grid { h :: Double, -- MUST BE GREATER THAN ZERO!
-                   function_values :: Values3D }
+                   function_values :: Values3D,
+                   cube_grid :: CubeGrid }
           deriving (Eq, Show)
 
 
@@ -40,24 +41,23 @@ instance Arbitrary Grid where
 make_grid :: Double -> Values3D -> Grid
 make_grid grid_size values
     | grid_size <= 0 = error "grid size must be positive"
-    | otherwise = Grid grid_size values
+    | otherwise = Grid grid_size values (cubes grid_size values)
 
 
 -- | Creates an empty grid with grid size 1.
 empty_grid :: Grid
-empty_grid = Grid 1 empty3d
+empty_grid = make_grid 1 empty3d
 
 
 -- | Returns a three-dimensional array of cubes centered on the grid
---   points of g with the appropriate 'FunctionValues'.
-cubes :: Grid -> CubeGrid
-cubes g
+--   points (h*i, h*j, h*k) with the appropriate 'FunctionValues'.
+cubes :: Double -> Values3D -> CubeGrid
+cubes delta fvs 
   = array (lbounds, ubounds)
            [ ((i,j,k), cube_ijk)
                  | i <- [0..xmax],
                    j <- [0..ymax],
                    k <- [0..zmax],
-                   let delta = h g,
                    let tet_vol = (1/24)*(delta^(3::Int)),
                    let cube_ijk =
                          Cube delta i j k (make_values fvs i j k) tet_vol]
@@ -67,7 +67,6 @@ cubes g
        zmax = zsize - 1
        lbounds = (0, 0, 0)
        ubounds = (xmax, ymax, zmax)
-       fvs = function_values g
        (xsize, ysize, zsize) = dims fvs
 
 
@@ -82,7 +81,7 @@ cube_at g i j k
     | j >= ysize = error "j >= ysize in cube_at"
     | k < 0      = error "k < 0 in cube_at"
     | k >= zsize = error "k >= zsize in cube_at"
-    | otherwise = (cubes g) ! (i,j,k)
+    | otherwise = (cube_grid g) ! (i,j,k)
       where
         fvs = function_values g
         (xsize, ysize, zsize) = dims fvs
-- 
2.43.2