hpwl
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Macro Placement by Wire-Mask-Guided Black-Box Optimization
The development of very large-scale integration (VLSI) technology has posed new challenges for electronic design automation (EDA) techniques in chip floorplanning. During this process, macro placement is an important subproblem, which tries to determine the positions of all macros with the aim of minimizing half-perimeter wirelength (HPWL) and avoiding overlapping. Previous methods include packing-based, analytical and reinforcement learning methods. In this paper, we propose a new black-box optimization (BBO) framework (called WireMask-BBO) for macro placement, by using a wire-mask-guided greedy procedure for objective evaluation. Equipped with different BBO algorithms, WireMask-BBO empirically achieves significant improvements over previous methods, i.e., achieves significantly shorter HPWL by using much less time. Furthermore, it can fine-tune existing placements by treating them as initial solutions, which can bring up to 50% improvement in HPWL. WireMask-BBO has the potential to significantly improve the quality and efficiency of chip floorplanning, which makes it appealing to researchers and practitioners in EDA and will also promote the application of BBO.
Advancing Routing-Awareness in Analog ICs Floorplanning
Basso, Davide, Bortolussi, Luca, Videnovic-Misic, Mirjana, Habal, Husni
The adoption of machine learning-based techniques for analog integrated circuit layout, unlike its digital counterpart, has been limited by the stringent requirements imposed by electric and problem-specific constraints, along with the interdependence of floorplanning and routing steps. In this work, we address a prevalent concern among layout engineers regarding the need for readily available routing-aware floorplanning solutions. To this extent, we develop an automatic floorplanning engine based on reinforcement learning and relational graph convolutional neural network specifically tailored to condition the floorplan generation towards more routable outcomes. A combination of increased grid resolution and precise pin information integration, along with a dynamic routing resource estimation technique, allows balancing routing and area efficiency, eventually meeting industrial standards. When analyzing the place and route effectiveness in a simulated environment, the proposed approach achieves a 13.8% reduction in dead space, a 40.6% reduction in wirelength and a 73.4% increase in routing success when compared to past learning-based state-of-the-art techniques.
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Piano: A Multi-Constraint Pin Assignment-Aware Floorplanner
Xu, Zhexuan, Zhou, Kexin, Wang, Jie, Geng, Zijie, Xu, Siyuan, Kai, Shixiong, Yuan, Mingxuan, Wu, Feng
--Floorplanning is a critical step in VLSI physical design, increasingly complicated by modern constraints such as fixed-outline requirements, whitespace removal, and the presence of pre-placed modules. However, traditional floorplanners often overlook pin assignment with modern constraints during the floorplanning stage. In this work, we introduce Piano, a floorplanning framework that simultaneously optimizes module placement and pin assignment under multiple constraints. Specifically, we construct a graph based on the geometric relationships among modules and their netlist connections, then iteratively search for shortest paths to determine pin assignments. This graph-based method also enables accurate evaluation of feedthrough and unplaced pins, thereby guiding overall layout quality. T o further improve the design, we adopt a whitespace removal strategy and employ three local optimizers to enhance layout metrics under multi-constraint scenarios. Experimental results on widely used benchmark circuits demonstrate that Piano achieves an average 6.81% reduction in HPWL, a 13.39% decrease in feedthrough wirelength, a 16.36% reduction in the number of feedthrough modules, and a 21.21% drop in unplaced pins, while maintaining zero whitespace. Floorplanning is the first step in modern VLSI physical design as it needs to determine the shape and location of large circuit modules on a chip canvas, while assigning the pins to each module's boundary for inter-module connections, thereby laying the foundation for subsequent detailed placement and routing stages.
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A Appendix
Macros are relatively large, including DRAMs, caches, and IO interfaces. Pins are input/output interfaces for modules and are connected by wires directly, which have A net contains a set of pins connected by the same wires. Pins from the same net can form a net bounding box as Fig.8 It is the sum of half perimeter of net bounding boxes as Fig.8 (a)(b), where We give a set of placement results to explain the metrics in Fig.8. The density of Fig.8 (c) is 2.0 because g Relationship between pin offset and HPWL. The pin offset can affect the HPWL.