1. Abstractions Abstractions for: – Architectures – Applications – Are others: Runtime environment, … ??? Do they depend on the metrics of interest? – (Performance, power, reliability, …) Abstractions can (have to) be defined on different levels Alternative abstractions on similar levels are possible Different objectives determine which abstractions are appropriate to use (Higher) Abstractions should be (more) Machine/Application/Implementation independent ‘Instantiating’ more abstract models becomes more difficult – Depends on level of accuracy needed

2. Abstractions for Architectures - Gaps Intermediate architectural models applicable to different actual systems – More general than detailed node/processor architectures – More specific then “Lantency, Bandwidth”-type models – Aka “Skeleton architectures” No agreed ‘dictionary’ or standards for intermediary level of abstractions How do we generate parameters for such abstractions

3. Abstractions for Applications - Gaps Code abstractions (executable code) – Proxies, Skeletons, Mini-Apps, Kernels, Dwarves/Motifs, synthetic benchmarks – Specific implementations to general descriptions (independent of programming models, languages, etc) are needed in different situations Lack of common and agreed collections – Automated generation only very limited possible – Verification of “representativeness” (expressive power) is lacking (non- existing) Descriptive abstraction (‘parametric’ representation) – Working set size, memory traffic, temporal/spatial localities, computation intensities on all levels, I/O, … – Lacking machine independent definitions (“agreed upon”) – How do you determine relevance, expressiveness, completeness, … – How do we iterate on defining them to arrive at relevant and minimal set Statistical significance (?) – How do you (auto)-generate and validate models based on them

4. Generation of Abstractions and Models How do we generate/instantiate our models – Mostly manual, need more (semi)-automatic – What are the basis for generation Top down: based on specification and ‘concepts’ Bottom up: based on measurements, counters, ‘data’ – How do we define/generate (concept of) abstraction by themselves Situations with many characterizing parameters - how to select/simplify them Analyzing complex execution behavior

5. Nathan Tallent Jim Kahle Lizy John Lenny Oliker Jeff Vetter Erich Strohmaier Kalyan Kumaran