An Effective Floorplanning Algorithm in Mixed Mode Placement Integrated with Rectilinear- Shaped Optimization for Soft Blocks Changqi Yang, Xianlong Hong, Hannah Yang EDA Lab, Tsinghua University Strategic CAD Labs, Intel Corporation

Content Motivation Outline of the Floorplan Algorithm RSF Experimental Results Summary

Mixed Mode Placement Mixed Mode Placement (MMP) problem can be successfully solved by combining floorplanning and cell based placement according to circuit's hierarchy. Motivation – Partition – Floorplan – Placement

Floorplanning is the Key Stage in MMP Floorplanning is the key phase during the whole design stages of MMP because the shorter wire length of floorplanning can reduce the final wire length after global / detailed placement. Restricting virtual blocks’ shapes to be fixed or be rectangular will limit the quality of floorplanning. Motivation

Previous Works Soften virtual blocks by changing their width and height – 2000, Ma, “VLSI floorplanning with Fixed Topology” L/T shaped floorplanning – 2001, Ma, "Floorplanning with Abutment Constraints..." Grid-based floorplanning algorithm to optimize the shape of virtual blocks – 2000, Dinesh P. Mehta, "On the Use of Flexible,..." Lagrange Relaxation method to modify the shapes and dimensions of modules to fill up the unused area of a preliminary floorplanning – 2002, F.Y.Young, "Non-rectangular shaping and sizing..." Motivation

Virtual Block Virtual blocks are composed by standard cells. Virtual blocks’ features: – They can expand their area – They can be transformed into rectilinear-shape. – They connect to other blocks through virtual pins. Motivation

Main Flow Outline of Algorithm

RSO MBB - Minimal Bounding Box – The half-perimeter of this bounding box is corresponding to the minimal wire length of the net in half-perimeter mode MBBI – Minimal Bounding Box Intersection – The virtual pin can be allocated at the point of intersection between the MBB and the virtual block which the virtual pin belongs to DSA – Dead Space Attachment – RSO can reduce the wire length if it can result in the smaller MBB of nets. It starts from searching DSB during the packing and then attaches the DSB to the virtual blocks properly. Outline of Algorithm

MBB & MBBI The minimal wire length of a net is: Draw a MMB according to the formula MBB would retrogress to be a line Find MBB with rectilinear-shaped block by enumerating all MBB candidates among sub blocks and selecting the one with minimal perimeter. Outline of Algorithm

Find the Dead Space CBL is adopted as the representation of blocks’ topology. In CBL, all the dead-space blocks can be found during the process of packing. Outline of Algorithm

DSA Gain: Potential Gain: Outline of Algorithm

DSA Algorithm Algorithm DSA() DS: the set of DSB in packing { construct DS during packing according to lemma 3; for each D in DS do for each attachment do calculate G according to formula (2); calculate G ' according to formula (3); end for select an attachment A with maximal G; if G(A)>0 then complete this attachment; else select an attachment A with maximal G ' ; if G ' (A) > 0 then complete this attachment; end if end for } Outline of Algorithm

Results on MCNC Cases Experimental Results Name WireLen Min/Ave r Virtual # 20% Virtual #50% Virtual #100% Min/AverImpr (%)Min/AverImpr (%)Min/AverImpr (%) ami / / / / / / / 53.2 ami / / / / / / / 37.9 apte / / / / / / / 43.9 xerox / / / / / / / 55.5

Results on MMP Circuits#cells #macro blocks #nets Block area (average) /cell area(average) block block block block block Experimental Results

Results on MMP (2) Name HMMP WireLen MMP WireLen Impr( %) HMMP RTime(s) MMP RTime(s) block e61.608e block e61.435e block e61.409e block92.345e61.552e block e61.240e Experimental Results

Summary The floorplanning algorithm integrated with rectilinear-shaped optimization is effective. It can achieve good floorplanning quality when virtual blocks exist. The MMP involving the algorithm as its floorplanning stage can obtain better performance in final placement results Summary

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