For several years, it has been economically and technically feasible to build parallel systems that scale from tens to hundreds of processors. By necessity tools embody knowledge of the execution environment, identifying performance bottlenecks or logical program errors in terms of application code constructs and their interaction with the execution environment. Experience comes with time, as tool developers understand the common programming idioms, the interactions of application code and the underlying hardware and software, and the user interfaces best suited for relating these...