I am doing rigorous accuracy tests of Octave functions comparing with MATLAB.
I used to think Octave to be clone of MATLAB. But there I found many
mismatches.
I used to think Octave to be subset of MATLAB but that's not totally true
because sometimes
Octave's function doing much more than MATLAB's same function. Was it all
time like
this? Is it intended?
Octave is an independent program designed to be m-code compatible. It is considered to be a bug if an incompatibility is found with MATLAB processed m-code, but Octave functions are not limited by MATLAB's operation. Ideally, Octave would be a superset of MATLAB function, with perfect compatibility where they overlap. In practice, the available function set only covers those features that Octave's volunteer contributors have chosen to implement. And in those cases attempting to create compatibility can be a challenge especially with the infinite possibilities for implementing some numerical operations. Last, maintaining Matlab compatibility is of course a moving target as new releases come out twice a year.
If you are finding places with particular levels of numerical error or in accuracy, those should be reported as bugs so that they can be addressed if practical