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[Octave-bug-tracker] [bug #56752] Performance slowdown from version 3.2.


From: anonymous
Subject: [Octave-bug-tracker] [bug #56752] Performance slowdown from version 3.2.4 through to current dev branch
Date: Thu, 12 Sep 2019 10:59:48 -0400 (EDT)
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:69.0) Gecko/20100101 Firefox/69.0

Follow-up Comment #42, bug #56752 (project octave):

@Rik, I am not sure whether other uses of NoAlias should also be changed.

All the instances that you found appear to be of the form 


octave_value_list retval;
NoAlias<Array<T>> r;
do_stuff ();
retval (0) = r;
return retval;


I am not sure in this case 

1) whether retval (0) = r; requires a copy
2) whether avoiding use of NoAlias would allow 
   the compiler to avoid the copy

(My guess is the copy does not happen in this case or is at most a shallow
copy)

On the other hand I see the implementation of NoAlias itself can be simplified
(as suggested by the FIXME comment) as we now require c++11.

Patch to simplify NoAlias is attached.

(file #47491)
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Additional Item Attachment:

File name: open_0qtoU59a.txt              Size:1 KB
    <https://savannah.gnu.org/file/open_0qtoU59a.txt?file_id=47491>



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