[Octave-bug-tracker] [bug #52706] Rewrite xpow.cc using templates

[John W. Eaton]

Follow-up Comment #8, bug #52706 (project octave):

I assume you mean things like this that appear in Array.h?


    octave_idx_type i;
    for (i = 0; i < len - 3; i += 4)
      {
        octave_quit ();

        p[i] = fcn (m[i]);
        p[i+1] = fcn (m[i+1]);
        p[i+2] = fcn (m[i+2]);
        p[i+3] = fcn (m[i+3]);
      }

    octave_quit ();

    for (; i < len; i++)
      p[i] = fcn (m[i]);


Instead of duplicating code like this many times, maybe we could do this loop
unrolling job with a template as well?

Also, I would not worry too much about calling octave_quit every time through
a loop if the loop does any substantial amount of work since it is a function
that should be easily inlined to be a check on a global variable.  Nothing
more should happen unless an signal has been caught.  Maybe that affects
performance enough to notice, but if it does, then I suspect we should be
unrolling the loop more than 4 times.

We could also probably gain something by properly using function parameters in
templates instead of function pointers.  This may not apply to xpow.cc, but I
think it does in other places like bsxfun.cc.

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