[Octave-bug-tracker] [bug #59711] Performance of `cd` is bad on Windows

[Markus Mützel]

Update of bug #59711 (project octave):

                  Status:               Confirmed => Ready For Test         

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Follow-up Comment #16:

I tried a different approach that should not be breaking API compatibility:
If I get it right, instead of calling "canonicalize_file_name" for every entry
(including private, +namespace and @class folders) in the load path, it uses
it earlier on for the "main" folder that is in the load path.
To check which impact that has and whether this is a step in the correct
direction, I locally added some commands to output to std::cout wherever
"canonicalize_file_name" could be removed with this approach, ran `make check`
and counted how often that string was printed. I used that as the baseline. On
my system, I counted 56212 calls.
After the described change, I added similar output commands wherever
"canonicalize_file_name" is now called *instead* (and where it wasn't called
before) and ran `make check` again with the same configuration. This time, I
counted 3734 calls. So for the test suite, that means a reduction by a factor
of approximately 15. (But keep in mind that there are other locations in the
code where "canonicalize_file_name" is used which aren't counted in either
test.)
I don't know how representative the test suite is though.

I also cross-compiled for Windows and ran the test suite there. All tests
still pass.
And `pkg load ltfat` still "feels" faster than with Octave 6.1.
So I pushed the change to stable here:
https://hg.savannah.gnu.org/hgweb/octave/rev/8b65dc1fd34d

Marking as ready for test.
It would be interesting to hear from people who reported slow performance.
What is their experience with a nightly build from tomorrow 2021 Jan 18 or
later?

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