Wirelength Minimization for Min-Cut Placements via Placement Feedback

Abstract—The advent of strong multilevel partitioners has made top–down min-cut placers a favored choice for modern placer implementations. Terminal propagation is an important step in min-cut placers because it translates partitioning results into global-placement wirelength assumptions. In this work, the repartitioning problem is carefully reexamined (Proc. ACM/IEEE Int. Symp. Physical Design, p. 18, 1997) in the context of terminal propagation and studied in an in-depth manner. Abstractly, it was observed that in repartitioning, future cell locations are used for present terminal propagations and that this can be conceptually regarded as a form of placement feedback. This concept was utilized to achieve accurate terminal propagation via feedback iteration and controller insertion to fine-tune the feedback response. This yields substantial reductions in placement wirelength. Implementing our approach in Capo [version 8.7 (Proc. ACM/IEEE Design Automation Conf., p. 477, 2000 and GSRC Bookshelf)] and applying it to standard benchmark circuits yields up to 14% wirelength reductions for the IBM benchmarks with an average improvement of 5.5 % and up to 10 % reductions for the Peko benchmarks with an average improvement of 5.37%. Experiments also show consistent improvements for routed wirelength, yielding up to 9 % wirelength reductions and 5.8 % average reduction with acceptable increase in placement runtime. In practice, the method proposed significantly improves routability without building congestion maps and also reduces the number of vias. Index Terms—Min-cut partitioning, routing, terminal propagation, VLSI placement. I

A framework for fine-grain synthesis optimization of operational amplifiers

This thesis presents a cell-level framework for Operational Amplifiers Synthesis (OASYN) coupling both circuit design and layout. For circuit design, the tool applies a corner-driven optimization, accounting for on-chip performance variations. By exploring the process, voltage, and temperature variations space, the tool extracts design worst case solution. The tool undergoes sensitivity analysis along with Pareto-optimality to achieve required specifications. For layout phase, OASYN generates a DRC proved automated layout based on a sized circuit-level description. Morata et al. (1996) introduced an elegant representation of block placement called sequence pair for general floorplans (SP). Like TCG and BSG, but unlike O-tree, B*tree, and CBL, SP is P-admissible. Unlike SP, TCG supports incremental update during operation and keeps the information of the boundary modules as well as their relative positions in the representation. Block placement algorithms that are based on SP use heuristic optimization algorithms, e.g., simulated annealing where generation of large number of sequence pairs are required. Therefore a fast algorithm is needed to generate sequence pairs after each solution perturbation. The thesis presents a new simple and efficient O(n) runtime algorithm for fast realization of incremental update for cost evaluation. The algorithm integrates sequence pair and transitive closure graph advantages into TCG-S* a superior topology update scheme which facilitates the search for optimum desired floorplan. Experiments show that TCG-S* is better than existing works in terms of area utilization and convergence speed. Routing-aware placement is implemented in OASYN, handling symmetry constraints, e.g., interdigitization, common centroid, along with congestion elimination and the enhancement of placement routability