Tree-Traversal Orientation Analysis

This paper presents a profiling-based analysis to determine the traversal orientation of link-based tree data structures. Given the very-high memory-hierarchy latencies in modern computers, once the compiler has identified that a pointer-based data structure represents a tree, it would be useful to determine the predominant orientation of traversal for the tree. Optimizing compilers can implement the static shape analysis proposed by Ghiya and Hendren to determine if a linked data structure is a tree [10]. However no techniques have been reported to enable an optimizing compiler to determine the predominant traversal orientation of a tree. This paper describes an analysis that collects data during an instrumented run to determine if the traversal is predominantly breadth-first or depth-first. The analysis determined, with high accuracy, the predominant orientation of traversal of trees in programs written by us as well as in the Olden benchmark suite. This profile-based analysis is storage efficient — it uses only 7% additional memory in comparison with the non-instrumented version of the code. Determining the predominant orientation of traversal of a tree data structure will enable several client optimizations such as improved software-based prefetching, data-storage remapping and better memory allocators.