How to look at the source code for MATLAB's built-in sort function?

Question

Joe 2013-5-1

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评论： Walter Roberson 2020-9-30

I need to find the big O runtime for MATLAB's built-in sort function, but I'm not quite sure how to if I don't even know how the function is coded. Is there some way to look at the code for the function because I know for some built-in functions you are able to look at the source code.

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Answer 1

Jonathan Epperl 2013-5-1

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If the source code is available, then

edit sort

will do the job. I can't check right now, but you go ahead and try that.

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Answer 2

Walter Roberson 2013-5-1

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编辑：Walter Roberson 2013-5-1

To look at the source code, get a job or internship with Mathworks.

sort() is a built-in; you cannot "edit sort" to look at it.

There are a number of routines for which MATLAB calls into LAPACK or BLAS when the arrays are large enough to make it worth the overhead. I do not know if sort() is one of those. If it is, then the LAPACK sort algorithm is at http://www.netlib.org/lapack/explore-html/de/de5/slasrt_8f_source.html

I have doubts about that being the appropriate routine, as it appears to only support a single data-type.

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Answer 3

Muhammad Ahsan Zahid 2020-4-14

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编辑：Muhammad Ahsan Zahid 2020-4-14

If you want to see the sourcee code behind the function, open the function as:

open function_name.m

Example

open rand.m

If available it will show you.

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Claudia Romero Rodriguez 2020-9-30

Actually it does show the code

Walter Roberson 2020-9-30

built-in (/Applications/MATLAB_R2020a.app/toolbox/matlab/datafun/@double/sort) % double method

edit sort will show you only documentation, unless you specifically open, for example, toolbox/matlab/datatypes/categorical/@categorical/sort.m .

But even that one does its work by using categoricalsort which is matlab.internal.categoricalUtils.categoricalsort.categoricalsort which is a build-in method.

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Answer 4

Chien-Han Su 2019-12-21

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I'm not sure whether this is what you need, I would recommend you to record (by tic and toc) and analyze the exceution time to find the Big-O since you can't not get the source code of built-in function, like this

iterStart = 10; % drop the first ten iterate 
iterNum = 1000;
N = 1000;
t = zeros(iterNum,N);
for m = iterStart:iterNum
    for n = 1:N
        a = rand(1,n);
        tic;
        b = sort(a);
        t(m,n) = toc;
    end 
end 
tAvg = mean(t,1);  
tAvg = tAvg/tAvg(1); % normalize
plot(1:N,tAvg)
xlabel('n');
ylabel('Normalized Time')
title('Normalized Execution Time for Sorting a Vector');