From 22fdc981284d235d7b3402b4f3e38dcbc848f725 Mon Sep 17 00:00:00 2001
From: Steven Robertson <steven@strobe.cc>
Date: Sun, 20 Nov 2011 10:08:13 -0500
Subject: [PATCH] Fix point swapping.

---
 cuburn/code/iter.py | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/cuburn/code/iter.py b/cuburn/code/iter.py
index 73b2808..aed2099 100644
--- a/cuburn/code/iter.py
+++ b/cuburn/code/iter.py
@@ -275,7 +275,10 @@ void iter(
         {{endfor}}
             apply_xf_{{std_xforms[-1]}}(x, y, color, rctx);
 
-        int sw = (threadIdx.y * 32 + threadIdx.x * 33) & {{NTHREADS-1}};
+        // Rotate points between threads.
+        int swr = threadIdx.y + threadIdx.x
+                + (round & 1) * (threadIdx.x / {{NTHREADS / 32}});
+        int sw = (swr * 32 + threadIdx.x) & {{NTHREADS-1}};
         int sr = threadIdx.y * 32 + threadIdx.x;
 
         swap[sw] = fuse ? 1.0f : 0.0f;