Fast Division/Modulo Operation

[silentlights]

Hi,
Is there a possibiliy to improve division or Modulo operations in the
following,

tmp1 = 123;
tmp2 = 123;
frame[8] = ((char)((tmp1/100)+48)); // Division
tmp1 = (tmp2 % 100); // Mod
frame[9] = ((char)((tmp1/10)+48));
tmp1 = (tmp2 % 10);

tmp 1& 2 are unsigned int and frame is a char array.

This is in a 16bit environment. I cant use any math libraries. Is there a
possibility of shifting or subtration methods..?

Thanks in advance.
Densil

[CBFalconer]

Re: Fast Division/Modulo Operation

silentlights wrote:[color=blue]
>
> Is there a possibiliy to improve division or Modulo operations in
> the following,
>
> tmp1 = 123;
> tmp2 = 123;
> frame[8] = ((char)((tmp1/100)+48)); // Division
> tmp1 = (tmp2 % 100); // Mod
> frame[9] = ((char)((tmp1/10)+48));
> tmp1 = (tmp2 % 10);
>
> tmp 1& 2 are unsigned int and frame is a char array.
>
> This is in a 16bit environment. I cant use any math libraries. Is
> there a possibility of shifting or subtration methods..?[/color]

Search google for an article I wrote in roughly the past month or
two. The subject included "double dabble", and was either here or
in comp.arch.embed ded or comp.programmin g.

--
A: Because it fouls the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

[silentlights]

Re: Fast Division/Modulo Operation

Hi,
For a beginer, your article

http://www.talkaboutprogramming.com/group/comp.programming/messages/189873.html

is not so clear to be implemted on this particular problem. Could you
please explain me a bit more relevant to this question.

Thanks
Densil

[Dik T. Winter]

Re: Fast Division/Modulo Operation

In article <fd716cf0a8ddb0 8accff2429e8463 c07@localhost.t alkaboutprogram ming.com> "silentligh ts" <silentlights@y ahoo.co.uk> writes:[color=blue]
> Hi,
> Is there a possibiliy to improve division or Modulo operations in the
> following,
>
> tmp1 = 123;
> tmp2 = 123;
> frame[8] = ((char)((tmp1/100)+48)); // Division
> tmp1 = (tmp2 % 100); // Mod
> frame[9] = ((char)((tmp1/10)+48));
> tmp1 = (tmp2 % 10);
>
> tmp 1& 2 are unsigned int and frame is a char array.[/color]

tmp1 *= 41;
f8 = (tmp1 >> 12) + 48;
tmp1 = (tmp1 & 0x0fff) * 10;
f9 = (tmp1 >> 12) + 48;
tmp1 = ((tmp1 & 0x0fff) * 10) >> 12;

works as long as tmp1 is smaller than 1000 initially.
--
dik t. winter, cwi, kruislaan 413, 1098 sj amsterdam, nederland, +31205924131
home: bovenover 215, 1025 jn amsterdam, nederland; http://www.cwi.nl/~dik/

[Dik T. Winter]

Re: Fast Division/Modulo Operation

In article <Hw9oLD.CCE@cwi .nl> "Dik T. Winter" <Dik.Winter@cwi .nl> writes:[color=blue]
> In article <fd716cf0a8ddb0 8accff2429e8463 c07@localhost.t alkaboutprogram ming.com> "silentligh ts" <silentlights@y ahoo.co.uk> writes:[color=green]
> > Hi,
> > Is there a possibiliy to improve division or Modulo operations in the
> > following,
> >
> > tmp1 = 123;
> > tmp2 = 123;
> > frame[8] = ((char)((tmp1/100)+48)); // Division
> > tmp1 = (tmp2 % 100); // Mod
> > frame[9] = ((char)((tmp1/10)+48));
> > tmp1 = (tmp2 % 10);
> >
> > tmp 1& 2 are unsigned int and frame is a char array.[/color]
>
> tmp1 *= 41;
> f8 = (tmp1 >> 12) + 48;
> tmp1 = (tmp1 & 0x0fff) * 10;
> f9 = (tmp1 >> 12) + 48;
> tmp1 = ((tmp1 & 0x0fff) * 10) >> 12;[/color]

Ok, if you also want to eliminate all multiplications :

tmp1 += ((tmp1 << 2) + tmp1) << 3;
f8 = (tmp1 >> 12) + 48;
tmp1 &= 0x0fff;
tmp1 += tmp1 << 2;
f9 = (tmp1 >> 11) + 48;
tmp1 &= 0x0fff;
tmp1 += tmp1 << 2;
tmp1 >>= 10;
--
dik t. winter, cwi, kruislaan 413, 1098 sj amsterdam, nederland, +31205924131
home: bovenover 215, 1025 jn amsterdam, nederland; http://www.cwi.nl/~dik/

[E. Robert Tisdale]

Re: Fast Division/Modulo Operation

silentlights wrote:
[color=blue]
> Is there a possibility to improve division or Modulo operations
> in the following,
>
> tmp1 = 123;
> tmp2 = 123;
> frame[8] = ((char)((tmp1/100)+48)); // Division
> tmp1 = (tmp2 % 100); // Mod
> frame[9] = ((char)((tmp1/10)+48));
> tmp1 = (tmp2 % 10);
>
> tmp 1& 2 are unsigned int and frame is a char array.
>
> This is in a 16bit environment. I can't use any math libraries.
> Is there a possibility of shifting or subtraction methods..?[/color]

DIV(3) Linux Programmer’s Manual DIV(3)

NAME
div - computes the quotient and remainder of integer division

SYNOPSIS
#include <stdlib.h>

div_t div(int numer, int denom);

DESCRIPTION
The div() function computes the value numer/denom
and returns the quotient and remainder in a structure named div_t
that contains two integer members named quot and rem.

RETURN VALUE
The div_t structure.

CONFORMING TO
SVID 3, BSD 4.3, ISO 9899