Cell placement apparatus and method, and computer readable record medium having cell placement program recorded thereon

Claim 1

A cell placement apparatus for use in computer aided design automation, comprising: a restricted region specifying module specifying both a restricted region in which is restricted a cell activity ratio indicative of a ratio of a cell occupied area to a chip surface area and a cell maximum activity ratio of said restricted region; a restricted region managing module accepting for management said restricted region and said cell maximum activity ratio specified by said restricted region specifying module; and a cell placing module placing cells in such a manner that said cell activity ratio of said restricted region managed by said restricted region managing module does not exceed said cell maximum activity ratio, wherein let s 1 and s 2 be cell areas in a first region and a second region, respectively, which are obtained as a result of bisecting, s (=s 1 +s 2 ) be a total cell area, S 1 and S 2 be areas of said first region and said second region, respectively, S 1 (i) be an area of a portion belonging to said first region within an i-th restricted region, S 2 (i) be an area of a portion belonging to said second region within said i-th restricted region, and ρ(i) be a cell activity ratio specified for said i-th restricted region, then said cell placement control module figures out areas S 1 ( 0 ) and S 2 ( 0 ) of portions having no cell activity ratio restriction in said first region and said second region, respectively, from S 1 ( 0 )=S 1 −ΣS 1 (i) S 2 ( 0 )=S 2 −ΣS 2 (i) and wherein said cell placement control module then figures out an activity ratio ρ( 0 ) of a portion having no cell activity ratio restriction, from ρ( 0 )={(total cell area)−(total cell area of activity ratio specified regions))/(total area)=[s−Σ{ρ(i)×(S 1 (i)+S 2 (i)}]/S 1 ( 0 )+S 2 ( 0 ) and wherein said cell placement control module then figures out cell effective areas s 1 ′ and s 2 ′ in said first and second regions, respectively, based on said activity ratios ρ( 0 ) and ρ(i), from s 1 ′=ρ( 0 )×S 1 ( 0 )+Σ(ρ(i)×S 1 (i)) s 2 ′=ρ( 0 )×S 2 ( 0 )+Σ(ρ(i)×S 1 (i)) and wherein said cell placement control module then figures out converted areas S 1 ′ and S 2 ′ by proportionally dividing a total area of said first and second regions by ratios, to a total cell area s, of cell effective areas s 1 ′ and s 2 ′ in said first and second regions, respectively, using S 1 ′=(S 1 +S 2 )×(s 1 ′/s) S 2 ′=(S 1 +S 2 )×(s 2 ′/s) and wherein said cell placement control module then provides a control of grouping of cells effected by said partitioning based placing module so that an absolute value of a difference between ratios of cell areas s 1 and s 2 to said converted areas S 1 ′ and S 2 ′, respectively, of said first and second regions, respectively, satisfies a condition |s 1 /S 1 ′−s 2 /S 2 ′|≦α.