Model-Based IC Placement Refinement for Wire Length Accuracy
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Solution Overview
Problem
Current placement approaches in integrated circuit generation, such as the net half perimeter (NHP) method, are computationally efficient but ignore high fanout nets, while routing-inspired wirelength (RWL) models provide high accuracy but are impractically slow, failing to effectively assess the impact of component moves on wire lengths and congestion.
Innovation Solution
A model-based refinement method that selectively employs the RWL approach only when necessary, using the NHP approach initially and switching to RWL to quantify changes in wire lengths and perimeters, determining when the more computationally intensive RWL is required based on specific criteria.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the routing-inspired wirelength (RWL) model is used to assess component moves, then measurement precision of wire length changes is improved, but productivity deteriorates due to impractically slow computation
Solution Approach 1:
The patent applies partial action by using the accurate RWL model only for high fanout nets rather than all nets. The system identifies high fanout nets through perimeter change computations and applies RWL selectively to these critical nets, achieving accurate wire length assessment where needed while maintaining overall computational efficiency through the faster NHP approach for other nets.
2Productivity
If the net half perimeter (NHP) method is used for placement, then productivity is improved due to computational efficiency, but measurement precision deteriorates because high fanout nets are ignored
Solution Approach 1:
The patent applies local quality by differentiating the assessment approach based on net characteristics. High fanout nets receive the more accurate RWL model assessment, while other nets use the faster NHP method. This localized application of different precision levels optimizes the overall placement process accuracy without sacrificing unnecessary computational resources on low-impact nets.
3Measurement precision
If the RWL approach is selectively employed based on perimeter change criteria, then measurement precision of wire length changes is improved for high fanout nets, but device complexity increases due to the hybrid model selection process
Solution Approach 1:
The patent uses parameter changes (specifically perimeter change thresholds and fanout criteria) to automatically determine when to switch between NHP and RWL models. By monitoring computed parameters like perimeter change magnitude and net fanout values, the system dynamically selects the appropriate assessment model, managing complexity through objective parameter-based decision rules rather than subjective judgment.
Data Source
AI summary
A system and method of performing model-based refinement of a placement of components in integrated circuit generation select one of the components as a candidate component and postulate a move of the candidate component from an original position to a new position. The method includes defining nets associated with the candidate component. An initial perimeter and a new perimeter associated with each of the one or more nets are defined. The initial perimeter includes the candidate component at its original position and the new perimeter includes the candidate component at its new position. The method includes quantifying a change from the initial perimeter and the new perimeter and the original position and the new position, and obtaining a model of wires interconnecting the candidate component to the components of each of the nets. A result of the placement is provided for manufacture of the integrated circuit.