# MPI-I-93-142

## MOD m gates do not help on the ground floor

### Grolmusz, Vince

**MPI-I-93-142**. October** **1993, 13 pages. | Status:** **available - back from printing | Next --> Entry | Previous <-- Entry

Abstract in LaTeX format:

We prove that any depth--3 circuit with MOD m gates of unbounded fan-in on the lowest level, AND gates on the second, and a weighted threshold gate on the top

needs either exponential size or exponential weights to compute the {\it inner product} of two vectors of length $n$ over GF(2). More exactly we prove that $\Omega(n\log n)\leq \log w\log M$, where $w$ is the sum of the absolute values of the weights, and $M$ is the maximum fan--in of the AND gates on level 2. Setting all weights to 1, we got a trade--off between the logarithms of the top--fan--in and the maximum fan--in on level 2.

In contrast, with $n$ AND gates at the bottom and {\it a single} MOD 2 gate at the top one can compute the {\it inner product} function.

The lower--bound proof does not use any monotonicity or uniformity assumptions, and all of our gates have unbounded fan--in. The key step in the proof is a {\it random} evaluation protocol of a circuit with MOD $m$ gates.

Acknowledgement:** **

References to related material:

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**URL to this document: **http://domino.mpi-inf.mpg.de/internet/reports.nsf/NumberView/1993-142

**BibTeX**
`@TECHREPORT{``Grolmusz93b``,`

` AUTHOR = {Grolmusz, Vince},`

` TITLE = {MOD m gates do not help on the ground floor},`

` TYPE = {Research Report},`

` INSTITUTION = {Max-Planck-Institut f{\"u}r Informatik},`

` ADDRESS = {Im Stadtwald, D-66123 Saarbr{\"u}cken, Germany},`

` NUMBER = {MPI-I-93-142},`

` MONTH = {October},`

` YEAR = {1993},`

` ISSN = {0946-011X},`

`}`