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.\"  * $Source: /udir/touati/RCS/reduce_depth.1,v $
.\"  * $Author: sis $
.\"  * $Revision: 1.2 $
.\"  * $Date: 1992/05/06 19:04:01 $
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.XX
reduce_depth [-b] [-d #] [-g] [-r] [-s #] [-v #] [-R #.#] [-S #] [-f #]
.PP
This command is to be used to improve the speed of a network before
technology mapping.  It performs a partial collapse of the network by
first clustering nodes according to some criteria and collapsing each
cluster into a single node. The clusters are formed as follows:  a
maximum cluster size is first computed, and the algorithm finds a
clustering that respects this size limit and minimizes the number of
levels in the network after the collapsing of the clusters. The size
limit is a limit on the number of nodes covered by the cluster, and
does not take into account the complexity of the nodes. Therefore this
command should only be used on networks decomposed into simple gates.
The cluster size limit can be provided in a variety of ways, 
depending on which option is used.
.PP
The \fB-b\fP option performs the clustering under the duplication ratio 
constraint specified by \fB-R\fP option.
.PP
The \fB-d #\fP option specifies the desired depth of the network after
clustering. The depth counts the number of nodes. Since each node
is expressed as a sum-of-products, specifying depth of 1 corresponds
to collapsing the network to two levels of logic. The algorithm
computes the minimum cluster size limit that yields a depth of \fBn\fR.
.PP 
The \fB-g\fP option prints out statistics based on cluster sizes.  No
clustering is done.
.PP
The \fB-r\fP option specifies a modification of the clustering
algorithm that produces the same number of logic levels but with less
duplication of logic.
.PP
The \fB-s #\fP option specifies the desired cluster size limit.
.PP
The \fB-v #\fP option specifies a verbosity level. It is used mainly for
debugging. 
.PP
The \fB-R #.#\fP option specifies the maximum duplication ratio.  The default is 2.0.
.PP
The \fB-S #\fP option specifies the smallest cluster size limit that
produces the same depth as a cluster size limit of \fBn\fR.
.PP
The \fB-f #\fP option specifies a cluster size limit in terms
of the number of fanins of the cluster. Its intended use is
for table-lookup FPGAs. It is a poor man's version of FlowMap.
