rd This book reports the scientific proceedings of the 23 International Symposium on High Performance Computing Systems and Applications. HPCS 2009 was held at Queen's University at Kingston, June 14-17, 2009. The symposium was hosted by HPCVL in co-operation with Compute Canada. The symposium brought together over 150 scientists from many countries including Brazil, Canada, China, UK, Germany and the USA. As the proceedings demonstrate, their work addresses fundamental HPC-related issues, from programming, to archit- tures, to applications and, finally, to upcoming challenges for HPC. In...