Re: A86: Sorry Dux. =-|

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Re: A86: Sorry Dux. =-|




Tercero wrote:

> First of all thanks for pointing out my terrible mistake.
> I did manage to resurrect it though.  Keep reading.
>
> Russian Peasant's Algorithm:
> made by Dux Gregis
> modified and renamed by Tim Farrell
>         (head recently buried in sand, not picking sand from ears and nose)
> nitpicked by Kirk Meyer
> scrutinized by RabidCow
> slaughtered by Dux Gregis
> Resurrected by Tim Farrell
>
> > I don't know if you tested this or not, but this doesn't work.
>
> I did test it.  However, I only tested it by loading 2 into b.  It
> worked then (and only then).
>
> > The algorithm works like this:
>
> Had you not explained this I couldn't have corrected it.
>
> > Also, I thought about it and decided that more time can be saved over
> > all if you check which of the input numbers is smallest before the
> > routine.  Otherwise, 179*0 will loop 7 times when it really doesn't need
> > to loop at all.
>
> Done.
>
> > Here's the Russian Peasants' Algorithm again (I doubt there's anything
> > that will speed it up):
>
> Doubt your doubts and believe your beliefs.
> This routine is 8 bytes bigger.  But when doing
> your 9*5 problem mine comes out 32 ticks faster.
> Check for yourself.  If I'm wrong please tell me,
> I hate to be wrong.

200 * 6 would loop an extra 5 times.  It's difficult to say whether or not it's
best to include a check like this.  I suppose that someone could check it
before they run the routine if they think it's necessary.

>
>
> ;African Swallow Algorithm_________________________
> ;Input: hl * b                                    |
> ;Output: hl                                       |
> ;Destroys: a, b, de                               |
> ;Size: 27 bytes                                   |
> ;--------------------------------------------------
> ASMult:
>         xor a
>         ld d, a
>         ld e, a
>         cp b
>         jp z, Bzero
>         cp l
>         jp nz, ASTop
>         cp h
>         ret z
> ASTop:
>         srl b
>         jp nc, ASkipadd
>         ex de, hl
>         add hl, de

you need ex de,hl again here

> ASkipadd:
>         ret z
>         add hl, hl
>         jp ASTop
> Bzero:
>         ld h, a
>         ld l, a
>         ret
> --
> Tercero  --  Email: mailto:tercero@busprod.com
>
> "The stone the builders rejected has become the capstone;"
>                         --Psalms 118:22
> "Everyone who falls on that stone will be broken to pieces,
> but he on whom it falls will be crushed."
>                         --Luke 20:18
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