- better accuracy for InvSqrt thanks to new coeff and 8 bytes less (h…

…ttp://www.multiwii.com/forum/viewtopic.php?f=8&t=4246&p=51412#p51412) git-svn-id: http://multiwii.googlecode.com/svn/trunk/MultiWii_shared@1679 02679b44-d973-9852-f2fa-63770883b36c
cedlecomte · Jun 3, 2014 · b8e209c · b8e209c
1 parent 0b48d6b
commit b8e209c
Showing 1 changed file with 2 additions and 2 deletions.
diff --git a/IMU.cpp b/IMU.cpp
@@ -156,8 +156,8 @@ float InvSqrt (float x){
     float   f; 
   } conv; 
   conv.f = x; 
-  conv.i = 0x5f3759df - (conv.i >> 1); 
-  return 0.5f * (conv.f * (3.0f - x * conv.f * conv.f));
+  conv.i = 0x5f1ffff9 - (conv.i >> 1); 
+  return conv.f * (1.68191409f - 0.703952253f * x * conv.f * conv.f);
 }
 
 // signed16 * signed16