在Python中列表操作(List manipulation in python)

 我最终在http://www.infoq.com/articles/Rails-Performance （“看看Rails中的常见性能问题”）中阅读了一篇优秀的文章。 然后我按照作者的建议在请求处理期间缓存计算： 
 
def estimated_costs
  @estimated_costs ||=
    begin
      # tedious vector math
    end
end
 
 因为我的工作表一遍又一遍地处理上面的内容，然后基于这些结果来计算更多的行，这使得蝙蝠的加速度提高了90％ 。 本来应该是平淡无奇的，但它开始只有几个总数，然后我把原型展示给了客户，并且从那里开始滚动:) 
 
 我还想知道基于数组的数学可能是低效的，所以我用NArray（ http://narray.rubyforge.org/ ）替换了数组的Ruby数组。 加速是微不足道的，但代码更清洁，所以它保持这种方式。 
 
 最后，我放置了一些对象缓存。 数据库中的“幻数”最多只会每年更改几次，其中一些已加密，但在大部分计算中需要使用它们。 这是缓慢成熟的缓慢果实，并且再削减1.25秒。 
 
 接下来我将着眼于加载关联，因为可能需要一些时间来保存，我会做一个简单的比较，发送“只是数据”与发送HTML，就像@tadman建议的那样。 关于我可以缓存的唯一部分是导航边栏。 所有其他内容取决于请求参数。 
 
 感谢您的建议！ 

I ended up reading an excellent article at http://www.infoq.com/articles/Rails-Performance ("A Look At Common Performance Problems In Rails"). Then I followed the author's suggestion to cache computations during request processing:
 
def estimated_costs
  @estimated_costs ||=
    begin
      # tedious vector math
    end
end
 
Because my worksheet does stuff like the above over and over, and then builds on those results to calculate some more rows, this resulted in a 90% speedup right off the bat. Should have been plain as day, but it started with just a few totals, then I showed the prototype to the customer, and it snowballed from there :)
 
I also wondered whether my array-based math might be inefficient, so I replaced the Ruby Arrays of numbers with NArray (http://narray.rubyforge.org/). The speedup was negligible but the code's cleaner, so it's staying that way.
 
Finally, I put some object caching in place. The "magic numbers" in the database only change a few times a year at most, and some of them are encrypted, but they need to be used in most of the calculations. That's low-hanging fruit ripe for caching, and it shaved off another 1.25 seconds.
 
I'll look at eager loading of associations next, as there's probably some time to save there, and I'll do a quick comparison of sending "just the data" vs sending the HTML, as @tadman suggested. About the only partial I can cache is the navigation sidebar. All of the other content depends on the request parameters.
 
Thanks for your suggestions!