[Octave-bug-tracker] [bug #56752] Performance slowdown from version 3.2.4 through to current dev branch

[John W. Eaton]

Follow-up Comment #43, bug #56752 (project octave):

The shallow copy of the array isn't the real problem.  It's that even if there
is no other copy and the reference count is always 1, the usual array indexing
operations for non-const instances of our copy-on-write classes must always
check the reference count.  The NoAlias class provides a way to override that
choice, but it is risky because we have to know that there will never be a
copy.  If we know that, then I think it makes sense to just use xelem
explicitly.

Another way to avoid the reference count checks is to use const copy-on-write
objects wherever possible.  We probably don't follow that advice as much as we
should in the Octave sources.


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