Approximate IC Placement via Probability Distributions
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Solution Overview
Problem
Current placement methods for integrated circuit design, such as minimum cut/partitioning, quadratic programming, force-directed, analytic, and simulated annealing, face issues with stability, speed, and quality of results, failing to provide a balance between fast and stable performance while optimizing objectives like wirelength and density.
Innovation Solution
The method employs probability distribution functions to approximate the placement of standard cells, macro-blocks, and I/O pads, gradually localizing these distributions to satisfy placement constraints and optimize objective functions, incorporating global optimization steps and refinement operations to improve runtime and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If minimum cut/partitioning based methods are used, then placement speed is improved, but stability and quality of results deteriorate
Solution Approach 1:
The placement process is divided into multiple refinement stages. Each stage applies different optimization strategies to progressively improve the placement solution. This segmentation allows the system to achieve both speed (through coarse initial placement) and stability (through iterative refinement), resolving the contradiction between fast placement and stable results.
Solution Approach 2:
The system performs preliminary placement using fast minimum cut/partitioning methods to establish an initial solution, then applies subsequent refinement operations to improve stability and quality. This preliminary action provides a fast baseline while leaving room for iterative improvements that enhance reliability without significantly increasing total runtime.
2Speed
If quadratic programming based methods are used, then placement speed is improved, but quality of results deteriorates
Solution Approach 1:
The placement optimization is segmented into multiple refinement stages that progressively improve solution quality. The system starts with fast quadratic programming-based placement and then applies additional refinement operations (such as local search, simulated annealing, or analytical methods) to progressively improve placement quality while maintaining reasonable runtime through the segmentation of the optimization process.
Solution Approach 2:
The system continuously refines the placement solution through multiple iterative improvement steps. Rather than relying on a single placement method, the system continuously applies refinement operations that build upon the initial quadratic programming solution, progressively improving quality while the overall process remains efficient due to the continuous nature of the refinement.
3Manufacturing precision
If analytic placement methods are used, then quality of results is improved, but placement speed deteriorates
Solution Approach 1:
The system segments the placement process into a fast initial placement phase (using minimum cut or quadratic programming) followed by multiple refinement phases (using analytical methods). This segmentation allows the system to achieve high quality results through analytical methods while maintaining speed by limiting the application of computationally intensive methods to only the refinement stages rather than the entire placement process.
Solution Approach 2:
The system performs preliminary placement using faster methods to establish an initial solution, then applies analytical placement methods as a refinement step. This preliminary action provides a fast baseline placement that reduces the computational burden required for subsequent analytical refinement, thereby achieving high quality results without proportionally increasing total runtime.
4Reliability
If force-based placement methods are used, then stability is improved, but placement speed deteriorates
Solution Approach 1:
The system segments the placement process to apply force-based methods only as a refinement technique rather than the primary placement method. The initial placement uses faster minimum cut or quadratic programming methods, and then force-based refinement is applied iteratively to improve stability. This segmentation allows the system to benefit from the stability of force-based methods without suffering from their slowness, as they are applied only to refine rather than compute the entire placement.
Data Source
AI summary
Disclosed are method, system, and computer program product for a method and system for a fast and stable placement/floorplanning method that gives consistent and good quality results. Various embodiments of the present invention provide a method and system for approximate placement of various standard cells, macro-blocks, and I/O pads for the design of integrated circuits by approximating the final shapes of the objects of interest by one or more probability distribution functions over the areas for the objects of interest with improved runtime and very good stability. These probability distributions are gradually localized to final shapes satisfying the placement constraints and optimizing an objective function.


