[Octave-bug-tracker] [bug #59702] Octave 6 slower then Octave 5 ?

[Markus Mützel]

Follow-up Comment #3, bug #59702 (project octave):

I ran the line with `dlmread` in a loop while I attached a profiler to the
Octave process.

Most of the time is spent in the function `setlocale` in the Microsoft Visual
C Run Time (msvcrt).
The innermost function in one of Octave's libraries that calls this function
is `Z20octave_read_fp_valueIdEdRSi`. I tried to demangle that symbol [1] but
was unsuccessful.
It is probably an instance of the templated function here:
https://hg.savannah.gnu.org/hgweb/octave/file/ed1a8af4242f/liboctave/util/lo-utils.cc#l242

The top of the call stack reads the following in Very Sleepy CS:

setlocale       msvcrt  [unknown]       0       0x7ffd9c349c3d
ZSt14__convert_to_vIdEvPKcRT_RSt12_Ios_IostateRKPi      libstdc++-6     
[unknown]       0       0xdd4e1c
ZNKSt7num_getIcSt19istreambuf_iteratorIcSt11char_traitsIcEEE6do_getES3_S3_RSt8ios_baseRSt12_Ios_IostateRd
       libstdc++-6     [unknown]       0       0xd359f9
ZNSi10_M_extractIdEERSiRT_      libstdc++-6     [unknown]       0       0xd59a7e
Z20octave_read_fp_valueIdEdRSi  liboctave-8     [unknown]       0       
0x6d2325aa
Z8FdlmreadRN6octave11interpreterERK17octave_value_listi liboctinterp-8  
[unknown]       0       0x6f93e056


It's not (yet) clear to me why that would need a call of `setlocale`, why it
is so slow, and why it looks like it was faster in the past.
Might be caused by a different version of GCC that we used for compiling
Octave 5.2 and Octave 6.1.

[1]: https://demangler.com/

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