GEnie@willett.UUCP (ForthNet articles from GEnie) (12/22/89)
Category 14, Topic 6 Message 37 Thu Dec 21, 1989 R.BERKEY [Robert] at 01:00 PST (This is being reposted to get into the Usenet port.) To: Philip Koopman Re: Signed Integer Division I'd like to see your analysis that symmetrical division is faster than floored division. I've looked at division a lot, and there's an absence of programming examples that use the symmetrical algorithm. I wonder if my posting describing an efficient algorithm for implementing division was passed along to you or possibly someone else at Harris. ------------ ----- This message came from GEnie via willett through a semi-automated program. Report problems to: 'uunet!willett!dwp' or 'willett!dwp@gateway.sei.cmu.edu'
koopman@a.gp.cs.cmu.edu (Philip Koopman) (12/23/89)
In article <75.UUL1.3#5129@willett.UUCP>, GEnie@willett.UUCP (ForthNet articles from GEnie) writes: > R.BERKEY [Robert] at 01:00 PST > I'd like to see your analysis that symmetrical division is faster than floored > division. I've looked at division a lot, and there's an absence of > programming examples that use the symmetrical algorithm. > > I wonder if my posting describing an efficient algorithm for implementing > division was passed along to you or possibly someone else at Harris. The "normal" division methods based on non-restoring shift and add seem to favor symmetrical division. In this paradigm, you require a post- pass fudge factor to be applied if the division is to be floored. This takes either time, or extra hardware, or both. If your machine implements unsigned division as the universal division primitive (UM/MOD), this is certain to be the case. By the way, if floored division is implemented as the primary division algorithm on the RTX series of processors, it will break a lot of C code -- and having both algorithms fully supported by hardware is likely to be difficult. No, I never saw your algorithm -- please send it to me directly and I will be happy to look it over -- Thanks. Phil Koopman koopman@greyhound.ece.cmu.edu Arpanet 2525A Wexford Run Rd. Wexford, PA 15090 Senior Scientist at Harris Semiconductor. I don't speak for them, and they don't speak for me.