title: What does a high branch efficiency and low control flow efficiency indicate?
body: <p>I used Parallel Nsight 2.2 to profile my code written in CUDA 4.2. The result is: <strong>branch efficiency=0.9</strong>, while <strong>control flow execution efficiency=0.26</strong>.</p>
  
  <p>From the user guide, </p>
  
  <pre><code>Branch Efficiency=({Branches} - {Diverged Branches}) / {Branches}
  Control Flow Efficiency={Thread Instructions Executed} / {Instructions Executed} / {Warps Size}
  </code></pre>
  
  <p>I'm confused: isn't a higher branch efficiency implying that there are more active threads executing the same instruction within a warp and hence a higher control flow efficiency? and what does a high branch efficiency and low control flow efficiency indicate? Thanks a lot for any comment.</p>