Pugh, WilliamData dependence distance is widely used to characterize data dependences in advanced optimizing compilers. The standard definition of dependence distance assumes that loops are normalized (have constant lower bounds and a step of 1); there is not a commonly accepted definition for unnormalized loops. We have identified several potential definitions, all of which give the same answer for normalized loops. There are a number of subtleties involved in choosing between these definitions, and no one definition is suitable for all applications. (Also cross-referenced as UMIACS-TR-93-133)en-USTechnical Report