32bit vs 64bit

Bingo right.ho at gmail.com
Wed Sep 17 15:42:55 UTC 2008

2008/9/17 Alan Evans <ame.fedora at gmail.com>

> On Wed, Sep 17, 2008 at 7:24 AM, Bingo <right.ho at gmail.com> wrote:
> > Read this for a comparison in performance for 32 bit, and 64 bit linux:
> >
> http://bingouv.blogspot.com/2008/08/desktop-linux-performance-comparison32.html
> > .
> Please don't take undue offence, but I don't think that your testing
> methodology sufficiently isolated the thing you were comparing. For
> example, your function for calculating factorials:
> define f (x) {
> if (x <= 1) return (1);
> return (f(x-1) * x);
> }
> Unless the tail recursion was optimized out of this, your result will
> likely be swamped by the overhead of much stack manipulation. And the
> fact that you used bc means that the the actual calculating is once or
> twice removed from the architecture.
> To be fair, you did recognize this in the last paragraph of your
> article. And I'm not saying that your comparisons have no value, just
> that their value is diminished for considering the difference between
> 32 and 64 bit processor architecture.
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Please criticize, this is the value I stand to gain from writing the
article: get more criticism.

I totally understand that bc is distant from the architecture because of
being an arbitrary precision calculator. No other calculator I tried could
hold factorial of multi-ten-thousand numbers so I had to choose bc. But
stack manipulation?

64 bit needs to be better at stack manipulation too if it is to perform
better, enough to matter to end users. So I did not shield 64 bit from this
responsibility. Nor do I want to shield bc from the responsibility of
optimizing for 64 bit systems. The review is about real programs, on real
OSes, real hardware doing (almost) real computation. So it will not make
excuses for them.

If some processor intensive tasks have sub-tasks that 64 bit is not
drastically better than 32 bit yet, it is only fair that this reflects in
the results. Though I'd like any suggestions about other tasks that can be
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