>>

>> I've been writing a series of articles on multi-word arithmetic for

>> Embedded Systems Programming magazine. I've gotten to the point of

>> integer division, and am looking for an algorithm that does fast

>> multi-word division. I've heard there's an iterative algorithm that's

>> used in some CPU's, but the only one I've been able to devise is not

>> fast enough.

>>

>> Can anyone point me in the right direction for such an algorithm?

>>

>> Thanks,

>>

>> Jack

>You might have Newton's method in mind. I used it decades ago on

>machines that didn't have divide instructions. See, for example, Knuth

>(The Art of Computer Programming, vol. 2, section 4.3.1) where some of

>the ideas in 'History and Bibliography' might be what you want. A

>similar approach is in Press, et al (Numerical Recipes in ..., section

>20.6). Note carefully that Newton's method for division requires a

>reasonably accurate initial estimate (within a factor of 2) for

>convergence.

>Lynn Killingbeck

Yes. You'll find an elegant example in Struble: Assembly-language

Programming for the IBM S/370, using the double-precision divider

to produce the initial approximation, and the quadruple precision

multiplier to produce the next iterate in quadruple precision.

OTOMH, it requires just a few steps.