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Re: Fixed-point arithmetic library

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On Wed, 22 Feb 2012, Jan Burse wrote:

> If a decimal scale suits you, you could use:
>
> http://docs.oracle.com/javase/7/docs/api/java/math/BigDecimal.html

Decimal would be fine. BigDecimal might actually be okay too.

I've actually misrepresented the context for this question slightly. My 
current place of work does a few calculations, and we currently use a 
fixed-point implementation of our own. However, it doesn't quite meet all 
our needs. My choice is really between extending it, and replacing it with 
something else. Being lazy, i would rather take advantage of someone 
else's hard work than do any myself.

Now, we wrote this fixed-point implementation having previously used 
BigDecimal, because we had some serious performance problems with that. 
This was before my time, so i'm very hazy on the details. I had already 
dismissed BigDecimal out of hand on the basis of that, but it might 
actually be worth looking at again.

I'd still be interested in any existing fixed-point libraries, as another 
option to consider.

tom

> Decimal scale means your numbers would be represented as:
>
>     mantissa * 10 ^ -scale
>
> Bye
>
> Tom Anderson schrieb:
>
>> I would quite like to represent some numbers in fixed point, and do
>> arithmetic with them.
>> 
>> These numbers will mostly not be more than a bilion, and will probably
>> never be more than a hundred billion. Some of them, i will need to
>> represent to eight decimal places. I'd like to be able to multiply two
>> large numbers, but i suspect will not need to multiply three. 11 * 2 + 8
>> = 30 decimal digits; that's about 100 bits, so 128 bits would be big
>> enough (about 5 decimal digits of headroom).
>> 
>> Can anyone suggest an existing library for doing fixed-point arithmetic
>> which would cover this?
>> 
>> I have googled, but not found anything. There are a few fixed-precision
>> libraries aimed at J2ME (i assume because old phones didn't have
>> floating-point units?). There's something called jExigo, but it's 64-bit
>> and the code doesn't look great.
>> 
>> It's quite possible that there is no such library. But i thought it
>> prudent to ask before writing one myself.

-- 
X is for ... EXECUTION!

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Fixed-point arithmetic library Tom Anderson <twic@urchin.earth.li> - 2012-02-22 21:39 +0000
  Re: Fixed-point arithmetic library Jan Burse <janburse@fastmail.fm> - 2012-02-22 22:59 +0100
    Re: Fixed-point arithmetic library Tom Anderson <twic@urchin.earth.li> - 2012-02-23 21:15 +0000
      Re: Fixed-point arithmetic library markspace <-@.> - 2012-02-23 13:53 -0800
      Re: Fixed-point arithmetic library Robert Klemme <shortcutter@googlemail.com> - 2012-02-23 23:21 +0100
      Re: Fixed-point arithmetic library Jan Burse <janburse@fastmail.fm> - 2012-02-24 00:02 +0100
  Re: Fixed-point arithmetic library Robert Klemme <shortcutter@googlemail.com> - 2012-02-22 23:13 +0100
    Re: Fixed-point arithmetic library Gene Wirchenko <genew@ocis.net> - 2012-02-22 14:59 -0800
      Re: Fixed-point arithmetic library Martin Gregorie <martin@address-in-sig.invalid> - 2012-02-23 01:05 +0000
        Re: Fixed-point arithmetic library Tom Anderson <twic@urchin.earth.li> - 2012-02-23 21:21 +0000
          Re: Fixed-point arithmetic library Gene Wirchenko <genew@ocis.net> - 2012-02-23 13:49 -0800
      Re: Fixed-point arithmetic library Tom Anderson <twic@urchin.earth.li> - 2012-02-23 21:16 +0000
        Re: Fixed-point arithmetic library Gene Wirchenko <genew@ocis.net> - 2012-02-23 14:03 -0800
          Re: Fixed-point arithmetic library Lew <noone@lewscanon.com> - 2012-02-23 14:42 -0800
            Re: Fixed-point arithmetic library Gene Wirchenko <genew@ocis.net> - 2012-02-23 15:08 -0800
        Re: Fixed-point arithmetic library Martin Gregorie <martin@address-in-sig.invalid> - 2012-02-23 23:05 +0000
    Re: Fixed-point arithmetic library glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-02-27 00:59 +0000
      Re: Fixed-point arithmetic library Arne Vajhøj <arne@vajhoej.dk> - 2012-02-26 20:50 -0500
        Re: Fixed-point arithmetic library Robert Klemme <shortcutter@googlemail.com> - 2012-02-27 07:32 +0100
          Re: Fixed-point arithmetic library Jan Burse <janburse@fastmail.fm> - 2012-02-27 13:46 +0100
  Re: Fixed-point arithmetic library Roedy Green <see_website@mindprod.com.invalid> - 2012-02-24 16:26 -0800

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