访问者在访问者模式中遍历对象结构时累积状态的好处以及访问者如何实现这一点？(Benefits of accumulating state during traversal of an object structure by a visitor in a visitor pattern and how can the visitor achieve this?)

 首先，这不是“NEON”。 这是内在的。 使用clang或gcc下的内在函数来获得良好的NEON性能几乎是不可能的。 如果你认为你需要内在函数，你应该手工编写汇编器。 
 
 vDSP不比NEON“更优化”。 iOS上的vDSP使用NEON处理器。 vDSP对NEON的使用比使用NEON要好得多。 
 
 我还没有挖掘出你的内在代码，但最可能的（事实上几乎肯定是）麻烦的原因是你正在创建等待状态。 在汇编程序中编写（内部函数只是用焊接手套书写的汇编程序），与C中写入内容无关。您不会循环。 你不会比较相同的。 你需要一种新的思维方式。 在汇编中，您可以一次执行多个任务（因为您有不同的逻辑单元），但是您绝对必须按照所有这些东西都可以并行运行的方式进行安排。 良好的装配保证了所有这些管道的完整。 如果你可以阅读你的代码，它非常合理，它可能是垃圾汇编代码。 如果你从不重复自己，那可能是废话汇编代码。 你需要仔细考虑什么是进入什么登记，以及有多少次循环，直到你被允许阅读。 
 
 如果它像音译C一样简单，那么编译器会为你做到这一点。 当你说“我要在NEON中写这篇文章”时，你会说“我认为我可以编写比编译器更好的NEON”，因为编译器也使用它。 也就是说，通常可以编写比编译器更好的NEON（特别是gcc和clang）。 
 
 如果你准备好潜入这个世界（这是一个非常酷的世界），你有一些阅读。 以下是我推荐的一些地方： 
 
 
 
 http://www.coranac.com/tonc/text/asm.htm （你真的想花一点时间用这个） 
 
 
 http://hilbert-space.de/ （整个网站，他很快就停止写作了。） 
  
 
   
 对于你的具体问题，他在这里解释它： http : //hilbert-space.de/?p=22 
 
  
 
 
 更多关于您的具体问题： 胳膊霓虹内在与手部装配 
 
 
 http://wanderingcoder.net/2010/07/19/ought-arm/ 
 
 
 http://wanderingcoder.net/2010/06/02/intro-neon/ 
 
 
 您也可能对。。。有兴趣： 
  
 
   
 http://robnapier.net/blog/fast-bezier-intro-701 
 
   
 http://robnapier.net/blog/faster-bezier-722 
 
  
 
 
 所有这些 ......始终始终始于重新考虑你的算法。 通常，答案不是如何让你的循环快速计算，而是如何经常调用循环。 

First, this is not "NEON" per-se. This is intrinsics. It is almost impossible to get good NEON performance using intrinsics under clang or gcc. If you think you need intrinsics, you should hand-write the assembler.
 
vDSP is not "better optimized" than NEON. vDSP on iOS uses the NEON processor. vDSP's use of the NEON is much better optimized than your use of the NEON.
 
I haven't dug through your intrinsics code yet, but the most likely (in fact almost certain) cause of trouble is that you're creating wait states. Writing in assembler (and intrinsics are just assembler written with welding gloves on), is nothing like writing in C. You don't loop the same. You don't compare the same. You need a new way of thinking. In assembly you can do more than one thing at a time (because you have different logic units), but you absolutely have to schedule things in such a way that all those things can run in parallel. Good assembly keeps all those pipelines full. If you can read your code and it makes perfect sense, it's probably crap assembly code. If you never repeat yourself, it's probably crap assembly code. You need to carefully consider what is going into what register and at how many cycles there are until you're allowed to read it. 
 
If it were as easy as transliterating C, then the compiler would do that for you. The moment you say "I'm going to write this in NEON" you're saying "I think I can write better NEON than the compiler," because the compiler uses it too. That said, it often is possible to write better NEON than the compiler (particularly gcc and clang).
 
If you're ready to go diving into that world (and it's a pretty cool world), you have some reading ahead of you. Here's some places I recommend:
 
 
 
http://www.coranac.com/tonc/text/asm.htm (You really want to spend some time with this one)
 
 
http://hilbert-space.de/ (The whole site. He stopped writting way too soon.) 
  
 
   
To your specific question, he explains it here: http://hilbert-space.de/?p=22
 
  
 
 
Some more on your specific question: Arm Neon Intrinsics vs hand assembly
 
 
http://wanderingcoder.net/2010/07/19/ought-arm/
 
 
http://wanderingcoder.net/2010/06/02/intro-neon/
 
 
You may also be interested in: 
  
 
   
http://robnapier.net/blog/fast-bezier-intro-701
 
   
http://robnapier.net/blog/faster-bezier-722
 
  
 
 
ALL THAT SAID... Always always always start by reconsidering your algorithm. Often the answer is not how to make your loop calculate quickly, it's how to not call the loop so often.