[Octave-bug-tracker] [bug #49940] The svd function takes very long time for big matrices

[Saleh]

URL:
  <http://savannah.gnu.org/bugs/?49940>

                 Summary: The svd function takes very long time for big
matrices
                 Project: GNU Octave
            Submitted by: sabmab
            Submitted on: Tue 27 Dec 2016 10:55:26 AM GMT
                Category: Performance
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Performance
                  Status: None
             Assigned to: None
         Originator Name: saleh
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: dev
        Operating System: GNU/Linux

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Details:

When running the svd function without returning parameter it perform well
(like Matlab).


tic;
svd(rand(3000));
toc;


When adding output parameters, the performance drops significantly(40x, in
this case), which is not the case in Matlab.
 

tic;
[u,s,v]=svd(rand(3000));
toc;


I didn't see this behavior for other functions such as the "inv" function.

 





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