## Fudging large value arithmetic in unfriendly languages

Expand Messages
• With 80-bit floats, and a 32*32- 64 integer multiply, the intel-using C/C++ and Asm programmers can without too much hassle write 62*62%62 bit mulmods.
Message 1 of 2 , Jul 2, 2002
With 80-bit floats, and a 32*32->64 integer multiply, the intel-using
C/C++ and Asm programmers can without too much hassle write 62*62%62
bit mulmods.

However, I plan to write some little factoring applets in JavaScript,
and it would be nice to know quite how far JS can be taken and remain
precise, without having to resort to multi-word operations, or
bit-by-bit operations?

Floating point multiplication with 52 bits of accuracy
Integer mutliplication with 32 bits of accuracy
=> maybe 84-bit intermediate exactly representable
=> 42*42%42 is probably pushing it.

Which is fairly poor for everything apart from squfof (which uses
half-length values almost the whole time).

I'm not intending the applets to be used in anger, obviously, but for
them to not be utterly useless would be quite nice.

I don't relish the thought of having to write a 'bignum' library in
JavaScript, to be honest. Does anyone have any experience hacking JS
to do such things?

Phil

=====
--
"One cannot delete the Web browser from KDE without
losing the ability to manage files on the user's own
hard disk." - Prof. Stuart E Madnick, MIT.
So called "expert" witness for Microsoft. 2002/05/02

__________________________________________________
Do You Yahoo!?
Yahoo! - Official partner of 2002 FIFA World Cup
http://fifaworldcup.yahoo.com
• ... using ... JavaScript, ... remain ... for ... Phil, Before I started programming in Java, I used Javascript for some of my calculators. At
Message 2 of 2 , Jul 2, 2002
--- In primenumbers@y..., Phil Carmody <thefatphil@y...> wrote:
> With 80-bit floats, and a 32*32->64 integer multiply, the intel-
using
> C/C++ and Asm programmers can without too much hassle write 62*62%62
> bit mulmods.
>
> However, I plan to write some little factoring applets in
JavaScript,
> and it would be nice to know quite how far JS can be taken and
remain
> precise, without having to resort to multi-word operations, or
> bit-by-bit operations?
>
> Does this sound about right?
> Floating point multiplication with 52 bits of accuracy
> Integer mutliplication with 32 bits of accuracy
> => maybe 84-bit intermediate exactly representable
> => 42*42%42 is probably pushing it.
>
> Which is fairly poor for everything apart from squfof (which uses
> half-length values almost the whole time).
>
> I'm not intending the applets to be used in anger, obviously, but
for
> them to not be utterly useless would be quite nice.
>
> I don't relish the thought of having to write a 'bignum' library in
> JavaScript, to be honest. Does anyone have any experience hacking JS
> to do such things?
>
>
> Phil
>

Phil,

Before I started programming in Java, I used Javascript for some of
my calculators.

At http://www.alpertron.com.ar/QUAD1.HTM you can see the source code
of my Quadratic Diophantine Equation solver in Javascript. It
includes multiple precision functions.

Notice that if you want to run the calculator in Javascript, you
should first disable Java (but not Javascript) and then point your
browser to: