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Fig. 1.
Flow of Kapees
bin have the same coordinates. At every level an arrangement of the bins in all
possible locations is performed. For the first level, entire circuit forms a bin and
is placed at the center. In the second level, there are four bins and 24 possible
ways of arranging the four bins in four locations. In the third level we have
4
4 = 16 bins. Here each bin in the third level is arranged in 24 ways within
the region of its parent bin.
The existing placers such as [2] and [10] typically carry out terminal prop-
agation. In terminal propagation, when the cells of circuit is partitioned into
two bins, dummy cells are introduced into each bins. These dummy cells are
included in external (cut) nets. When the two bins are possible candidate for
further partitioning, external nets carry information that they are connected to
a bin externally, and hence they do not get cut. As a result better wire length is
obtained. However, in our experiment with terminal propagation we did not find
noticeable improvement in the wire length resulting from terminal propagation
scheme. So we do not perform terminal propagation but instead swap and move
cells within bins. This is equivalent to improve upon the cuts obtained at Global
placement phase. We discuss Cell Swapping in section 3.2.
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