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In this paper, we present ObSteiner, an exact algorithm for the construction of obstacle-avoiding rectilinear Steiner minimum trees (OARSMTs) among complex rectilinear obstacles. This is the first paper to propose a geometric approach to optimally solve the OARSMT problem among complex obstacles. The optimal solution is constructed by the concatenation of full Steiner trees among complex obstacles, which are proven to be of simple structures in this paper. ObSteiner is able to handle complex obstacles, including both convex and concave ones. Benchmarks with hundreds of terminals among a large number of obstacles are solved optimally in a reasonable amount of time. [ABSTRACT FROM PUBLISHER]

This paper presents an efficient method to solve the obstacle-avoiding rectilinear Steiner tree (OARSMT) problem optimally. Our work is developed based on the GeoSteiner approach in which full Steiner trees (FSTs) are first constructed and then combined into a rectilinear Steiner minimum tree (RSMT). We modify and extend the algorithm to allow obstacles in the routing region. For each routing obstacle, we first introduce four virtual terminals located at its four corners. We then give the definition of FSTs with blockages and prove that they will follow some very simple structures. Based on these observations, a two-phase approach is developed for the construction of OARSMTs. In the first phase, we generate a set of FSTs with blockages. In the second phase, the FSTs generated in the first phase are used to construct an OARSMT. Finally, experiments on several benchmarks are conducted. Results show that the proposed method is able to handle problems with hundreds of terminals in the presence of multiple obstacles, generating an optimal solution in a reasonable amount of time. [ABSTRACT FROM PUBLISHER]

Rectilinear Steiner minimal tree (RSMT) problem finds a minimum length tree that interconnects a given set of points by only horizontal and vertical line segments and by using extra points if necessary. In this paper, to speedup the RSMT construction, two recently developed successful heuristic algorithms, namely rectilinear steiner tree (RST) by Zhou and batched greedy algorithm (BGA) by Kahng et al., have been used as the basis. Following a slight modification on RST, which led to a nonrecursive and a considerably faster version, a partially parallelized and distributed form of this modified algorithm is proposed. Computational tests using large random data sets have shown the advantage of the modification on RST, and tests conducted on a cluster of workstations have proven the proposed distributed approach to be very promising particularly for large problem instances. [ABSTRACT FROM AUTHOR]

Given a set of pins and a set of obstacles on routing layers, a multilayer obstacle-avoiding rectilinear Steiner minimal tree (ML-OARSMT) connects these pins by rectilinear edges within layers and vias between layers and avoids running through any obstacle to construct a Steiner tree with a minimal total cost. The ML-OARSMT problem is very important for many very large scale integration designs with pins being located in multiple routing layers that contain numerous routing obstacles incurred from IP blocks, power networks, prerouted nets, etc. As a fundamental problem with extensive practical applications to routing and wirelength/congestion/timing estimations in early design stages, it is desired to develop an effective algorithm for the ML-OARSMT problem to facilitate the design flow. However, there is no existing work on this ML-OARSMT problem. In this paper, we first formulate the ML-OARSMT problem with rectangular obstacles and then identify key different properties of this problem from its single-layer counterpart. Based on the multilayer obstacle-avoiding spanning graph, we present the first algorithm to solve the ML-OARSMT problem. Our algorithm can guarantee an optimal solution for any two-pin net and many multiple-pin nets. Experiments show that our algorithm results in 33% smaller total costs on average than a construction-by-correction heuristic which is widely used for Steiner-tree construction in the recent literature. [ABSTRACT FROM AUTHOR]

Given a set of pins and a set of obstacles on a plane, an obstacle-avoiding rectilinear Steiner minimal tree (OARSMT) connects these pins, possibly through some additional points (called the Steiner points), and avoids running through any obstacle to construct a tree with a minimal total wirelength. The OARSMT problem becomes more important than ever for modern nanometer IC designs which need to consider numerous routing obstacles incurred from power networks, prerouted nets, IP blocks, feature patterns for manufacturability improvement, antenna jumpers for reliability enhancement, etc. Consequently, the OARSMT problem has received dramatically increasing attention recently. Nevertheless, considering obstacles significantly increases the problem complexity, and thus, most previous works suffer from either poor quality or expensive running time. Based on the obstacle-avoiding spanning graph, this paper presents an efficient algorithm with some theoretical optimality guarantees for the OARSMT construction. Unlike previous heuristics, our algorithm guarantees to find an optimal OARSMT for any two-pin net and many higher pin nets. Extensive experiments show that our algorithm results in significantly shorter wirelengths than all state-of-the-art works. [ABSTRACT FROM AUTHOR]

Focuses on a study which examined Steiner-tree constructions for difficult instances to optimize the buffered tree resulting from the van Ginneken-style buffer insertion. Notation and problem formulation; Information on the proposed clustered tree algorithm; Experimental comparison.