[Octave-bug-tracker] [bug #51403] isequal is slow

[Mike Miller]

Follow-up Comment #2, bug #51403 (project octave):

Part of the slowness of __isequal__ may be that it is written to always
support variable arguments, while the most common case is just two arguments
being compared.

Compare the timings and the profiler output for these two ways of testing
whether two objects have the same class:


>> x = [];
>> y = x;
>> profile on
>> tic; for i=1:10000; strcmp (class (x), class (y)); endfor; toc
Elapsed time is 0.180546 seconds.
>> profile off
>> profshow
   #            Function Attr     Time (s)   Time (%)        Calls
------------------------------------------------------------------
   2               class             0.015      75.92        20000
   3              strcmp             0.005      23.51        10000
   5             profile             0.000       0.40            1
   4                 toc             0.000       0.07            1
   1                 tic             0.000       0.02            1
   6              nargin             0.000       0.02            1
   8               false             0.000       0.02            1
   7           binary !=             0.000       0.02            1
   9 __profiler_enable__             0.000       0.00            1
>> profile clear
>> arg_list = {y};
>> profile on
>> tic; for i=1:10000; strcmp (class (x), cellfun ("class", arg_list,
"uniformoutput", false)); endfor; toc
Elapsed time is 0.330531 seconds.
>> profile off
>> profshow
   #            Function Attr     Time (s)   Time (%)        Calls
------------------------------------------------------------------
   4             cellfun             0.063      58.65        10000
   5              strcmp             0.019      17.48        10000
   2               class             0.016      15.16        20000
   3               false             0.009       8.63        10001
   7             profile             0.000       0.05            1
   6                 toc             0.000       0.01            1
   1                 tic             0.000       0.00            1
   8              nargin             0.000       0.00            1
   9           binary !=             0.000       0.00            1
  10 __profiler_enable__             0.000       0.00            1


For the most common case of `isequal(x,y)`, y is still represented as varargin
and all comparisons are done using cellfun.

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