如何加快Matlab中的“排序”功能？ [英] How to speed up 'sort' function in Matlab?

问题描述

  [temp，Idx] = sort（M，2 ）; 
  

我想要得到每行M的排序索引，这是一个大小> 50k。

我努力搜索，但没有找到任何东西。如果您有任何意见，我们将不胜感激！

我会给你我的估计值：可能是Matlab的排序运行（在正确的向量化代码上，比如你的）和C ++一样快，而你刚刚看到运行一个采用O（n ^ 2 log n）的算法的效果。这是在Matlab的营销材料中报告其排序功能比C的qsort更快，但可以带上一点盐。

I was using the built-in sort function of Matlab:

[temp, Idx] = sort(M,2);

I would like to have the sorted index of each row of M, which is a matrix of size > 50k.

I searched hard but did not find anything.. It would be greatly appreciated if you have any comments!

解决方案

To get a sense of how much room for improvement you have, I would suggest writing a test program in C and use qsort or in C++ and user sort and carefully time it on 7000 inputs of size 7000 (or whatever setup you have in Matlab).

I'm going to give you my estimate: probably Matlab's sort runs (on properly vectorized code, like yours) as fast as C++, and you're just seeing the effect of running an algorithm that takes O(n^2 log n). It is reported in Matlab's marketing material that its sort function was faster than C's qsort, but take it with a grain of salt.

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