hmmm...8 bit shift register and a BCD counter....still discrete logic but not a ton of gates.
   
  Makes me wonder why anyone would do it in gates....8 pin PIC, serial data in, BCD out?

"Carlos A. Marcano V." <c.marcano@gmail.com> wrote:
  Nice link, Adam. Thanks.

I was looking for something less code-like and more hardware-like (TTL 
gates and similar) but it is a very interesting reading.

Regards,

*Carlos Marcano*
-Guri, Venezuela-

M. Adam Davis wrote:
> From
> http://my.opera.com/allbits/blog/show.dml/114980
> which has a whole slew of interesting operations.
> 
> It's a start.
> 
> ----------
> 13. Population Count (Ones Count)
> 
> The population count of a binary integer value x is the number of one
> bits in the value. Although many machines have single instructions for
> this, the single instructions are usually microcoded loops that test a
> bit per cycle; a log-time algorithm coded in C is often faster. The
> following code uses a variable-precision SWAR algorithm to perform a
> tree reduction adding the bits in a 32-bit value:
> 
> unsigned int
> ones32(register unsigned int x)
> {
> /* 32-bit recursive reduction using SWAR...
> but first step is mapping 2-bit values
> into sum of 2 1-bit values in sneaky way
> */
> x -= ((x >> 1) & 0x55555555);
> x = (((x >> 2) & 0x33333333) + (x & 0x33333333));
> x = (((x >> 4) + x) & 0x0f0f0f0f);
> x += (x >> 8);
> x += (x >> 16);
> return(x & 0x0000003f);
> }
> 
> ----------
>
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