Branch Strategies to Optimize Decision Trees for Wide-Issue Architectures

Abstract. Branch predictors are associated with critical design issues for nowadays instruction greedy processors. We study two important domains where the optimization of decision trees — implemented through switch-caseor nested ifthen-else constructs — makes the precise modeling of these hardware mechanisms determining for performance: compute-intensive libraries with versioning and cloning, and high-performance interpreters. Against common belief, the complexity of recent microarchitectures does not necessarily hamper the design of accurate cost models, in the special case of decision trees. We build a simple model that illustrates the reasons for which decision tree performance is predictable. Based on this model, we compare the most significant code generation strategies on the Itanium2 processor. We show that no strategy dominates in all cases, and although they used to be penalized by traditional superscalar processors, indirect branches regain a lot of interest in the cont...

• Type: Conference
• Year: 2004
• Where: LCPC
• Authors: Patrick Carribault, Christophe Lemuet, Jean-Thomas Acquaviva, Albert Cohen, William Jalby
• Keywords: Decision Tree, Instruction Greedy Processors, LCPC 2004, Nested Ifthen-else Constructs