copy-on-write, performance, and code readability

Question

matal 2013-11-26

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/107559-copy-on-write-performance-and-code-readability

回答： The Matlab Spot 2013-11-26

I use a global, multi-level nested struct() to hold a lot of data. For example, I have:

global DATA;
DATA.US.AAPL.date = <array of dates>
DATA.US.AAPL.px = <array of prices>

Exactly why I am using a structure like this or what I am storing in it is not relevant for this question. Above is just an example.

Inside of functions that operate on this structure, I often create an "alias":

function m = doStuff(region,ticker)
   global DATA;
   ldata = DATA.(region).(ticker);
   <work on and possibly update ldata>
   DATA.(region).(ticker) = ldata;
end

It's obvious that using an alias like ldata improves readability - however this appears to come at a cost. When DATA is large, replace ldata with direct DATA.(region).(ticker) leads to material performance improvement.

Presumably, the Matlab copy-on-write semantics is somehow to blame here.

Any thoughts as to how I can get readability and performance?