Handbook of Algorithms for Physical Design Automation part 33 provides a detailed overview of VLSI physical design automation, emphasizing state-of-the-art techniques, trends and improvements that have emerged during the previous decade. After a brief introduction to the modern physical design problem, basic algorithmic techniques, and partitioning, the book discusses significant advances in floorplanning representations and describes recent formulations of the floorplanning problem. The text also addresses issues of placement, net layout and optimization, routing multiple signal nets, manufacturability, physical synthesis, special nets, and designing for specialized technologies. It includes a personal perspective from Ralph Otten as he looks back on. | 302 Handbook of Algorithms for Physical Design Automation among the obvious facilitators instead certain existing steps in floorplacement are skipped. This improvement is based on two observations 1 blocks that are much smaller than their bin can be treated like standard cells and 2 the number of blocks that are large relative to the bin size is necessarily limited. For example there cannot be more than nine blocks with area in excess of 10 percent of a bin s area 30 . In selective floorplanning each block is marked as small or large based on a size threshold. Standard cells and small blocks can be clustered except that clusters containing hard blocks have additional restrictions on their aspect ratios. After successful annealing only the large blocks are placed fixed and considered obstacles. Normal top-down partitioning resumes and each remaining block will qualify as large at some later point. This way specific locations are determined when the right level of detail is considered Figure . If floorplanning fails during hierarchical placement the failed bin is merged with its sibling and the merged bin is floorplanned Figure . The blocks marked as large in the merged bin include those that exceed the size threshold and also those marked as large in the failed bin because the failure suggests that those blocks were difficult to pack . After the largest macros are placed the flow resumes 30 . Variables queue of placement partitions Initialize queue with top-level partition 1 While queue not empty 2 Dequeue a partition 3 If partition is not marked as merged 4 Perform look-ahead floorplanning on partition 5 If look-ahead floorplanning fails 6 Undo one partition decision 7 Merge partition with sibling 8 Mark new partition as merged and enqueue 9 Else if partition has large macros or is marked as merged 10 Mark large macros for placement after floorplanning 11 Cluster remaining macros into soft macros 12 Cluster std-cells into soft macros 13 Use fixed-outline
