Functional decomposition has recently been adopted for look-up tabel (LUT)-
based field-programmable gate array (FPGA) technology mapping with good res
ults. In this paper we propose a novel method to unify functional single;ou
tput and multiple-output decomposition. We first address a compatible class
encoding algorithm to minimize the number of compatible classes in the ima
ge function. After applying the encoding algorithm, we can therefore improv
e the decomposability in the subsequent decomposition of the; image functio
n. The above encoding algorithm is then extended to encode multiple-output
functions through the construction of a hyperfunction, Common subexpression
s among these multiple-output functions can be extracted during the decompo
sition of the hyperfunction, Consequently, we can handle multiple-output de
composition in the same manner as single-output decomposition. Experimental
results show that our algorithms are promising.