Different image bounds layout

1 files changed, 15 insertions, 10 deletions

diff --git a/aberth/aberth_kernel.fut b/aberth/aberth_kernel.fut
index fae1450..58b8838 100644
--- a/aberth/aberth_kernel.fut
+++ b/aberth/aberth_kernel.fut
@@ -128,11 +128,13 @@ let calc_index (value: f64) (left: f64) (right: f64) (steps: i32): i32 =
 
 let point_index
         (width: i32) (height: i32)
-        (top_left: complex) (bottom_right: complex)
+        (bottom_left: complex) (top_right: complex)
         (pt: complex)
         : i32 =
-    let xi = calc_index (c64.re pt) (c64.re top_left) (c64.re bottom_right) width
-    let yi = calc_index (c64.im pt) (c64.im bottom_right) (c64.im top_left) height
+    -- Range for 'yi' is reversed because image coordinates go down in the y
+    -- direction, while complex coordinates go up in the y direction
+    let xi = calc_index (c64.re pt) (c64.re bottom_left) (c64.re top_right) width
+    let yi = calc_index (c64.im pt) (c64.im top_right) (c64.im bottom_left) height
     in if 0 <= xi && xi < width && 0 <= yi && yi < height
         then width * yi + xi
         else -1
@@ -145,16 +147,19 @@ entry main_job
         : []i32 =
     -- Unnecessary to give each polynomial a different seed
     let rng = rand_engine.rng_from_seed [seed]
-    let top_left = c64.mk left top
-    let bottom_right = c64.mk right bottom
-    let indices = filter (\i -> i != -1) (flatten
+    let bottom_left = c64.mk left bottom
+    let top_right = c64.mk right top
+    let indices = flatten
             (map (\idx ->
                     let p = derbyshire_at_index idx
                     let (_, pts) = aberth.aberth p rng
-                    let indices = map (point_index width height top_left bottom_right) pts
-                    in indices)
-                 (start_index ..< start_index + num_polys)))
-    in reduce_by_index (replicate (width * height) 0) (+) 0 indices (replicate (length indices) 1)
+                    in map (point_index width height bottom_left top_right) pts)
+                 (start_index ..< start_index + num_polys))
+    let filtered = filter (\i -> i != -1) indices
+    in reduce_by_index (replicate (width * height) 0)
+                       (+) 0
+                       filtered
+                       (replicate (length filtered) 1)
 
 entry main_all
         (width: i32) (height: i32)