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From: johna@haddock.UUCP
Newsgroups: net.math
Subject: Re: need fast algorithm for reciprocal - (nf)
Message-ID: <195@haddock.UUCP>
Date: Mon, 25-Jun-84 23:37:50 EDT
Article-I.D.: haddock.195
Posted: Mon Jun 25 23:37:50 1984
Date-Received: Thu, 28-Jun-84 03:23:30 EDT
Lines: 32

#R:burl:-48000:haddock:13000001:000:902
haddock!johna    Jun 25 16:16:00 1984

The following is a division routine to divide 2 floating point numbers
that have up to 31 bit mantissas.  It uses only shifts, ORs, ANDs and
subtraction.

#define LO31BITS 0x7fffffff
#define BIT0 0x1
divide(dividend, divisor, quotient,
	 sign_dvd, sign_dvi, sign_quo, exp_dvd, exp_dvi, exp_quo)

	long dividend, divisor, quotient, sign_dvd, sign_dvi, sign_quo;
	long exp_dvd, exp_dvi, exp_quo;
{
	register short i;

	sign_quo = sign_dvd ^ sign_dvi;
	exp_quo  = exp_dvd - expdvi;
	quotient = 0;
	for (i=0; i<31; i++)
	{       quotient = (quotient << 1) & LO31BITS;          /* shift up */
		if (dividend >= divisor)                /* can we subtract? */
		{       dividend -= divisor;                  /* then do it */
			quotient |= BIT0;            /* set lo-order bit on */
		}
		dividend = (dividend << 1) & LO31BITS;          /* shift up */
	}
}

Hope this helps.
		      ...!cca!ima!haddock!johna