From e014df2b1a4b6fb0b633d736d8a63ee62309ce97 Mon Sep 17 00:00:00 2001
From: Nathan Vegdahl <cessen@cessen.com>
Date: Thu, 19 Mar 2020 09:59:19 +0900
Subject: [PATCH] Fix rare panic in Sobol sampler.

Due to the undefined behavior of shifting a number by its
bit-width, the Sobol sampler would panic when sample index
`1 << 15` was requested.

This fixes it without introducing any additional checks or
operations.
---
 sub_crates/sobol/src/lib.rs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/sub_crates/sobol/src/lib.rs b/sub_crates/sobol/src/lib.rs
index 086f282..0b07290 100644
--- a/sub_crates/sobol/src/lib.rs
+++ b/sub_crates/sobol/src/lib.rs
@@ -92,7 +92,8 @@ fn sobol_u32(dimension: u32, index: u32) -> u32 {
         let j = index.trailing_zeros();
         result ^= vecs[(i + j) as usize];
         i += j + 1;
-        index >>= j + 1;
+        index >>= j;
+        index >>= 1;
     }
 
     (result as u32) << 16