Add comment on potential impact on divergence

rapidsai · Jul 27, 2022 · e3a2134 · e3a2134
1 parent 047551d
commit e3a2134
Showing 1 changed file with 4 additions and 0 deletions.
diff --git a/cpp/include/cuspatial/experimental/detail/point_in_polygon.cuh b/cpp/include/cuspatial/experimental/detail/point_in_polygon.cuh
@@ -78,6 +78,10 @@ __device__ inline bool is_point_in_polygon(Cart2d const& test_point,
         T rise          = b.y - a.y;
         T rise_to_point = test_point.y - a.y;
 
+        // The divergence here is introduced to avoid a potential division
+        // of `rise` on the rhs of the comparison operator. The assumption here
+        // is that the the division instruction costs more cycles than the
+        // divergence to synchronize.
         if (rise > 0 && (test_point.x - a.x) * rise < run * rise_to_point)
           point_is_within = not point_is_within;
         else if (rise < 0 && (test_point.x - a.x) * rise > run * rise_to_point)