[Octave-bug-tracker] [bug #41453] norm is really slow for sparse matrices

[Mattias Linde]

URL:
  <http://savannah.gnu.org/bugs/?41453>

                 Summary: norm is really slow for sparse matrices
                 Project: GNU Octave
            Submitted by: linde
            Submitted on: Tue 04 Feb 2014 11:01:53 AM GMT
                Category: Octave Function
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Performance
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: dev
        Operating System: Any

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Details:

In many cases I've encountered, it is much faster to do 
norm( full( A ) )  
compared to just norm(A) when A is sparse.

Short test script and diary are attached. 
To avoid uploading testmatrices, the script uses random matrices, but the
problem is consistent and shows up every time.

Have tested this with octave 3.2.4, 3.6.0 and dev sources as of today, similar
results.

The speed difference I see is about a factor of 1000 and sometimes more.



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File Attachments:


-------------------------------------------------------
Date: Tue 04 Feb 2014 11:01:53 AM GMT  Name: slownorm.m  Size: 314B   By:
linde

<http://savannah.gnu.org/bugs/download.php?file_id=30452>
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Date: Tue 04 Feb 2014 11:01:53 AM GMT  Name: slownorm.txt  Size: 1kB   By:
linde

<http://savannah.gnu.org/bugs/download.php?file_id=30453>

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