Steve Fink wrote:
>
> On Mar-17, Benjamin Goldberg wrote:
> >
> > The answer to this question varies from platform to platform, and
> > I've only go windows to test on...
> >
> > If I do 32 "save"s in a row, this will certainly be slower than
> > doing a single "push".
> >
> > If I do 1 "save", this will (hopefully) be faster than 1 "push".
> >
> > How many "save"s does it take to be to be slower than one "push"?
> >
> > (When writing pasm by hand, what's a reasonable cutoff?)
>
> I would guess that about 256 million saves is the same as 8 million
> pushes, but that really depends on how much space an entry on the
> respective stacks take and how large your virtual address space can be
> -- because the only way to make them equivalent is to call enough of
> them to run out of memory and crash. :-)
Regarding memory:
Entries on the type-specific stacks consume no more memory than the
registers themselves.
Entries on the general stack (where save/restore goes) also have, in
addition to the saved register, an integer indicating the type of
register that's been saved, to prevent pushing an int and popping a
string.
Thus, 16 int save ops consume as much memory as one pushi, even
though the pushi is saving 32 int registers.
Regarding speed:
Each save is a (non-jit, non-inlined) function call.
Each push is a (non-jit, non-inlined) function call.
Even if there is *little* overhead for function calls, it's nonzero,
and it adds up.
> Sorry, I'm being obnoxious. You fell into the same trap as I recently
> did. pushx and save are not interchangeable; they operate on
> completely different stacks. 'save' pushes an entry of arbitrary type
> onto the user stack; pushi, pushs, and friends push onto type-specific
> register frame stacks.
>
> Somehow, this needs to be documented better, because it's quite
> surprising (to me, at least.)
Actually, I did realize that they go on completely different stacks.
What I didn't know (though I do now, thanks to Leopold's post) was their
relative speeds.
--
$a=24;split//,240513;s/\B/ => /for@@=qw(ac ab bc ba cb ca
);{push(@b,$a),($a-=6)^=1 for 2..$a/6x--$|;print "[EMAIL PROTECTED]
]\n";((6<=($a-=6))?$a+=$_[$a%6]-$a%6:($a=pop @b))&&redo;}
