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Recursive Bisection Placement*: feng shui 5.0

Recursive Bisection Placement*: feng shui 5.0. * We abandoned recursive bisection about 6 months ago…. Ameya R. Agnihotri Satoshi Ono Patrick H. Madden SUNY Binghamton CSD, FAIS, University of Kitakyushu

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Recursive Bisection Placement*: feng shui 5.0

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  1. Recursive Bisection Placement*: feng shui 5.0 * We abandoned recursive bisection about 6 months ago… Ameya R. Agnihotri Satoshi Ono Patrick H. MaddenSUNY Binghamton CSD, FAIS, University of Kitakyushu (with code by Mehmet Can Yildiz and Ateen Khatkhate, and with help from Purdue’s Cheng-Kok Koh and Chen Li) This work was supported by an IBM Faculty Partnership Award, SRC Project 947.1, an equipment grant from Intel, NYSTAR MDC, and by funds from the Japanese Ministry of ECSST via Kitakyushu and Fukuoka knowledge-based cluster project.

  2. Where is Kitakyushu?

  3. feng shui versionshttp://vlsicad.cs.binghamton.edu • 1.0: basic bisection engine • [ISPD99,GLSVLSI01] iterative deletion, cycling, terminal propagation work. • 1.5: cut sequence optimization • [DAC01] paper with Rent’s rule. • 2.0: Fractional cut • [ICCAD03] results close to annealing; possible to place very very dense. • 2.4, 2.6: Mixed size placement paper • [ISPD04] results improved by 26% on average over the closest competing tool. • 3.0: Structural (beacon) placer • [ASPDAC05] new method designed to have fun with the PEKO benchmarks; currently within 22% of optimal. • 5.0: Integration of tools • GUI front end, [GLSVSLI00] non-Manhattan global router, [DAC03] global router, [ISCAS05] delay analysis, PowerARC delay library, support for LEF/DEF, gate sizing tool… Versions of the stand-alone placer are available in both hMetis and MLPart flavors. • 5% or so improvements on mixed size placement (with minor tuning). • The bisection based placement engine is now in maintainence mode; we’ll fix minor problems, but it’s not our main focus.

  4. Bisection Based Placement Logic elements Semiconductor chip

  5. Fractional Cut Bisection

  6. Min cut (hMetis) Area Y Area Y Area X Area X Mixed Size Fractional Cut

  7. IBM01 before legalization

  8. Placement Legalization • Standard cells: • Dynamic programming approaches [ICCAD03], and an unpublished method. • Moving macro blocks: • [ISPD04] Extension of the tetris method by Hill. • Fixed macro blocks: • Fractured row legalization [Khatkhate MS thesis].

  9. ISPD04 Experimental Results As much as 51% better on some benchmarks. Closest is around 8%, for the design that doesn’t have macro blocks.

  10. Now about the contest… • The designs have very large amounts of internal white space (apples vs. oranges) • Space MUST be distributed internally to have any chance of a good result (due to fixed locations of the macro blocks) • We have no support at all for internal white space distribution • Or, to be more precise… The correct location for white space is usually outside of the core.

  11. Our contest result The rightanswer Example IBM

  12. Example

  13. How Much White Space Do You Really Need? • If you had 100X more space, would you really want to stretch that far? • Why do the industry guys do this? • Put space in early for sizing and routability • Or even better, use something like…. • [ICCAD04] cut line shifting for routability. • [ASPDAC05], same idea for gate sizing and buffer insertion. • We’ve integrated our global router and sizing tools with the placer to avoid needing to insert excess space.

  14. Placement Contest, Round 2 • We’re going to lose round 1; that’s for sure. • Apples vs. oranges problem; some of the apple placement methods are going to look very bad… • Who’s up for another round? • Moving macro blocks? • Rotation of blocks? • Mirroring cells? • Or round 1 again, but give me some time to finish the move away from recursive bisection! • Routing benchmark announcement • Patrick Groeneveld, Jurjen Westra, and myself, have been working on global routing benchmarking. We’ll talk about this at EDP. WANTED: more research groups in routing!

  15. Better Visualization (feng shui 5.0 GUI version) • Start with a “reference placement” • For the PEKOs, this is the known optimal • Map pixel colors from an image onto cells in the reference placement • Rearrange the cells to match a placement under study • Keep the cell colors from the reference

  16. Source Image (Prof. Jason Cong) Optimal placement for PEKO01 in the feng shui 5.0 GUI Image mapped onto the cells And then rearranged to match the placement of mPL Fun with the PEKOs If the placement is optimal, the mapped image should be identical to the reference image.

  17. feng shui 5.0Suboptimality Rogues Gallery mPL Dragon Capo feng shui Beacon 26% HPWL improvement on mixed size, fractional cut, non-Manhattan, and what do people ask about? The funny pictures from the GUI… Prof. Jason Cong Prof. Majid Sarrafzadeh Prof. Igor Markov Prof. Patrick H. Madden Satoshi Ono

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