Department of defense, Aerospace, Universities, Industry, Manufacturing (Illinois SmartState). This document reflects the thoughts of a group of highly talented individuals from universities, industry, and research labs on what might be the challenges in advancing computing by a thousand- fold by 2015. The work was sponsored by DARPA IPTO with Dr. William Harrod as Program Manager, under AFRL contract #FA8650-07-C-7724. The report itself was drawn from the results of a series of meetings over the second half of 2007, and as such reflects a snapshot in time. The goal of the study was to assay the state of the art, and not to either propose a potential system or prepare and propose a detailed roadmap for its development. Further, the report itself was assembled in just a few months at the beginning of 2008 from input by the participants. As such, all inconsistencies reflect either areas where there really are significant open research questions, or misunderstandings by the editor. There was, however, virtually complete agreement about the key challenges that surfaced from the study, and the potential value that solving them may have towards advancing the field of high performance computing.