Overview of Reversible Logic Synthesis Methods.

Such a variety of different reversible gates results in a variety of different approaches to reversible logic synthesis. Fortunately, the basic analysis of different techniques of reversible logic synthesis was successfully done in one of Perkowski's work. Here, we use and expand this approach to the classification of reversible synthesis methods.

Composition methods: The idea is to compose a reversible block using small and well known reversible gates. The reversible block should be easy to use. Then, a modification of a conventional logic synthesis procedure is applied to synthesize a network. The resulting network will be reversible as a network essentially consisting of reversible gates.

 Decomposition methods: Decomposition methods can be characterized as a top down reduction of the function from its outputs to its inputs. During the design procedure a function is supposed to be decomposed into a combination of several specific functions each of which is realized as a separate reversible network .An example of a decomposition method can be found in where synthesis appears to be a reduction of the output to the form of the input. The decomposition and composition methods can be multilevel. Observe that the composition and decomposition methods form a very general and powerful tool of logic synthesis. In fact, most of the algorithms can be classified as either composition or decomposition. Using Lemma 1, one can notice the duality of the composition and decomposition methods; a composition design procedure for a reversible function f is a decomposition procedure for f¡1.

 Factorization methods: Factorization is another powerful logic design tool. Its idea is in choosing a Boolean operation, for instance, ? (often multiplication or EXOR) for a function f and ¯ending two functions f1 and f2 such that:
 f = f1? f2;
 for the synthesis cost metrics the cost of f is smaller than the sum of costs of f1 and f2 plus a weight associated with the Operation. In general, the Operation does not have to be a binary operation, but may be an arbitrary multiple output function of several arguments. To our knowledge, the factorization tool was first applied to reversible logic design in.






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