[Octave-bug-tracker] [bug #61319] idivide fails to distinguish between ceil and floor for inputs close to perfect squares

[Michael Leitner]

Follow-up Comment #13, bug #61319 (project octave):

Markus, you are missing the x(y_sel) instead of x in the "floor" case. Apart
from that, it looks correct.

Yes, integer division is slower than floating-point division. But note that
C99 and later specifies that integer division rounds towards zero, that is,
what here seems to be the "fix" option. C++ (what octave is written in) seems
to be the same. However, octave integer division per default does what the
"round" mode does, thus there has to be some post-processing to be done on the
result of x/y (on the C++ level). What I do not get now is why it is not even
slower. On the other hand, there should be a way to speed up the "fix" case:
just use C++ integer division without the post-processing. Or am I missing the
point somewhere?

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