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- Newsgroups: comp.arch
- Path: sparky!uunet!stanford.edu!nntp.Stanford.EDU!rgupta
- From: rgupta@leland.Stanford.EDU (Rajesh Gupta)
- Subject: Re: Logic Minimization Algorithms
- Message-ID: <1992Dec15.225625.23933@leland.Stanford.EDU>
- Sender: rgupta@momus.Stanford.EDU (Rajesh Gupta)
- Organization: CIs, Stanford University, CA 94305, USA
- References: <1992Dec15.024904.22554@amd.com>
- Distribution: world
- Date: Tue, 15 Dec 92 22:56:25 GMT
- Lines: 65
-
- In article <1992Dec15.024904.22554@amd.com> roberts@angelo.amd.com (Dave Roberts) writes:
- >
- >
- > I couldn't think of a more appropriate news group to post this in, so
- > here goze:
- >
- comp.lsi.cad would be a more appropriate newsgroup.
-
- > What sort of algorithms are typically used to minimize logic equations
- > specified in high level hardware description languages (PAL software,
- > Verilog, etc.)?
- >
- > I've read and understand Quine-McClusky, and doodled around with
- > implementing my own versions. It seems to work well except for the
- > final step: choosing a set of prime implicants from the set that you
- > just produced (by reductions of the form x * y + x * ~y = x, for those
- > of you who don't remember. Prime implicants are those product terms
- > that can't be reduced any further by the application of the above
- > identity).
- >
- ...
- >
- > So I guess my question is, how are these problems overcome? Do people
- > use other algorithms than Quine-McClusky instead that don't suffer
- > these problems? If so, what are they?
- >
- > Does someone have references of articles that describe this stuff?
- > Articles themselves?
- >
-
-
- QM uses enumeration to achieve optimum. A number of heuristics
- achieve near optimal solutions using algebraic methods. Most common
- being the espresso-style heuristics which attempts to utilize implicit
- don't-cares (either by tautology-checking or by using approximate
- don't-care sets) to perform logic minimization.
-
- Two-level logic synthesis is a fairly well-developed field. You may
- want to check out the following monograph
-
- Brayton, Sangiovanni et al
- "Logic Minimization Algorithms for VLSI", Kluwer Academic, 1984 (I think)
-
-
- or there is a tutorial paper in IEEE Proceedings Feb 1990.
-
-
- > What about publicly available source code that implements the various
- > algorithms?
-
- Espresso and its cousins are publicly available. (Espresso: UCB,
- Bold: Colorado, Boulder).
-
- >
- > Thanks for any help people can give to satisfy my curiousity.
- >
- > Dave Roberts
-
-
-
- Rajesh Gupta
-
- 725-3647 CIS 18 rgupta@momus.stanford.edu
-
-
-