Re: Fast computation of parity

From: Mok-Kong Shen (mok-kong.shen_at_t-online.de)
Date: 12/31/03 

Date: Wed, 31 Dec 2003 02:02:06 +0100

Alexis Machado wrote:
>
> "Mok-Kong Shen" <mok-kong.shen@t-online.de> wrote:
> >
> > /* returns 0 if even parity, else 1 */
> > int Parityasm(unsigned int w)
> > { int p;
> >
> > __asm
> > {
> > mov eax,w
> > mov ebx,eax
> > shr ebx,16
> > xor eax,ebx
> > mov ebx,eax
> > shr ebx,8
> > xor eax,ebx
> > jp pr
> > mov p,1
> > jmp ee
> > pr:
> > mov p,0
> > ee:
> >
> > }
> >
> > return p;
> > }
>
> An alternative :
>
> MOV EAX, w
> MOV EBX, EAX
> BSWAP EAX
> XOR EAX, EBX
> XOR AL, AH
> SETPO AL /* AL=1 if parity is odd, AL=0 otherwise */
> AND EAX, 1 /* return EAX ... */

I tried it with VC++. It's slower. (BTW, I don't
yet know how to run under gcc a group of asm statements
(grouped by {} and with labels within it as is my code
above) and should appreciate help.)

M. K. Shen

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