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2024 ICCAD CAD Contest Problem B: �Power and Timing Optimization Using Multibit Flip-Flop

Problem Description, Benchmarks, and Results

2024-10-30

Sheng-Wei Yang, Jhih-Wei Hsu, Ting Wei Li, �Tzu-Hsuan Chen, Chin-Fang Cindy Shen

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CONFIDENTIAL INFORMATION

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Outline

Problem Description

Evaluation Methodology

Benchmarks

Results

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Outline

Problem Description

Evaluation Methodology

Benchmarks

Results

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Problem Description

Banking

Conglomerating multiple single-bit flip-flops into one multibit flip-flop is a useful technique for optimization

The movement is usually referred to as “banking”
Banking helps save power and area
May create dependencies on timing-critical paths

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banking

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Problem Description

Debanking

To take care of timing critical paths, sometimes tool needs to re-evaluate critical paths that end on banked multibit flip-flops.
This move is generally referred to as debanking
Trade-off between timing and power

Banking: Improve power & area. May sacrifice timing.
Debanking: Improve timing with power & area penalty.

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	1-bit FF	2-bit FF
Normalized Area	1	1.6
Normalized Power	1	1.7
Normalized Delay	1	2

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Problem Description

Specs for Contestants

Testcase Input

Simplified design with combinational gates and flip-flops

Contestants are allowed to:

Move or size flip-flops
Bank or debank flip-flops

Output should satisfy the following constraints:

All instances must be placed within die region.
All instances must be non-overlapping and on-site.
banking and debanking mapping list needs to be provided
Nets must remain functionally equivalent

No open or short nets.

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Outline

Problem Description

Evaluation Methodology

Benchmarks

Results

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Evaluation Methodology

Total Negative Slacks (TNS)

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Evaluation Methodology

Placement Legality Constraints

PlacementRows

Start from (<startX>, <startY>)
Has a <totalNumOfSites> of cell sites back-to-back placed horizontally
cell site: a small rectangle defined in PlacementRows with a dimension of (<siteWidth>, <siteHeight>)

On-site: cells with their bottom-left corner aligning to the site grid given from the PlacementRows
Cells should not overlap one another

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Evaluation Methodology

Cell Density Constraints

Placement Density Constraint

Design is divided into placement bin units
For each bin the total area of the cells could not exceed the described utilization rate
The objective is to produce a legalized placement solution
Contestants should legalize flip-flops within each bin

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Evaluation Methodology

Multiple Objective Optimization: Power, Performance, and Area (PPA)

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Outline

Problem Description

Evaluation Methodology

Benchmarks

Results

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Benchmarks

Testcase1: extracted from an initial opto design with only flip-flop datapath left.
Testcase2: extracted from a flatten design with initial opto and legalization done.
Testcase3: extracted from a flatten design with initial opto and legalization done.

Hidden testcases: design permutations from public testcases

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Specs	Testcase1	testcase2	testcase3	hidden1	hidden2	hidden3	hidden4
#Insts	108685	153457	101221	108685	153457	153457	101221
#Nets	104235	153934	104761	104235	153934	153934	104761
#FlipFlops	19876	21164	13016	19879	21164	21164	13016
Weight Factor	411680	519031	336142	411710	519031	519031	366142

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Outline

Problem Description

Evaluation Methodology

Benchmarks

Results

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Results

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Total Participants: 90 teams
Final Submissions: 44 teams
Submit with valid scores in at least one testcase: 41 teams

Team	Testcase1	testcase2	testcase3	hidden1	hidden2	hidden3	hidden4	Weighted �final score
1	693986404	745476	675559572	30175076	13212740	52124078	674676431	3107821
2	719733913	811024	693887313	30461537	13388840	54005613	693332444	3219048
3	690084983	835259	678819883	38930436	12555433	51444123	676665833	3258295
4	718444718	770638	691728642	41486870	15729265	52412042	689833099	3417434
5	711752359	814449	714627880	47948025	13958892	53565677	712609301	3494395
6	816288865	821653	803104066	38332727	12895728	59838790	799994828	3537665
7	727709964	719559	755949492	64544400	20782579	59036613	891296821	4108781

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Honorable Mentions

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Honorable Mention

Best Testcase2 Performance

Team: cadb1008

National Tsing Hua University

Yi-Ting Li

Wuqian Tang

Chi Hsu

Woei-Haur Hung

Prof. Ting-Chi Wang

Prof. Chun-Yao Wang

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Honorable Mention

Sixth place

Team: cadb1009

University of Wisconsin Madison

Aditya Das Sarma

Prof. Tsung-Wei Huang

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Honorable Mention

Fifth place

Team: cadb1051

The Chinese University of Hong Kong

Bangqi Fu

Yutao Wang

Xingyu Cui

Prof. Evangeline F.Y. Young

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Honorable Mention

Fourth place

Team: cadb1038

Fudan University

Benchao Zhu

Jiawei Li

Yang Liu

Prof. Jianli Chen

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Winners

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Third Place

Team: cadb0017

National Yang Ming Chiao Tung University

Huan-Yuan Chen

Lin Yu-Ruei

Yu-Chia Chen

Prof. Mark Po-Hung Lin

Prof. Hung-Ming Chen

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Second Place

Team: cadb0015

National Yang Ming Chiao Tung University

Chi-En Ho

Chieh-Yu Kuo

Wen-Yan Cheng

Prof. Hung-Ming Chen

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First Place

Team: cadb0027

Prof. Yao-Wen Chang

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Cheng-Yen Li	National Taiwan University
Chuan-Chi Su
Shao-Hsiang Chen
Zheng-Wei Chen	National Central University

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