ON ACC and threshold circuits

It is proved that any language in ACC can be approximately computed by two-level circuits of size 2 raised to the (log n)/sup k/ power, with a symmetric-function gate at the top and only AND gates on the first level. This implies that any language in ACC can be recognized by depth-3 threshold circuits of that size. This result gives the first nontrivial upper bound on the computing power of ACC circuits.<
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