8 research outputs found
Equality Saturation: A New Approach to Optimization
Optimizations in a traditional compiler are applied sequentially, with each
optimization destructively modifying the program to produce a transformed
program that is then passed to the next optimization. We present a new approach
for structuring the optimization phase of a compiler. In our approach,
optimizations take the form of equality analyses that add equality information
to a common intermediate representation. The optimizer works by repeatedly
applying these analyses to infer equivalences between program fragments, thus
saturating the intermediate representation with equalities. Once saturated, the
intermediate representation encodes multiple optimized versions of the input
program. At this point, a profitability heuristic picks the final optimized
program from the various programs represented in the saturated representation.
Our proposed way of structuring optimizers has a variety of benefits over
previous approaches: our approach obviates the need to worry about optimization
ordering, enables the use of a global optimization heuristic that selects among
fully optimized programs, and can be used to perform translation validation,
even on compilers other than our own. We present our approach, formalize it,
and describe our choice of intermediate representation. We also present
experimental results showing that our approach is practical in terms of time
and space overhead, is effective at discovering intricate optimization
opportunities, and is effective at performing translation validation for a
realistic optimizer.Comment: 80 pages, 39 figure
American College of Cardiology; American Heart Association Task Force; European Society of Cardiology Committee for Practice Guidelines. ACC/AHA/ESC 2006 guidelines for management of patients with ventricular arrhythmias and the prevention of sudden cardiac death: a report of the American College of Cardiology/American Heart Association Task Force and the European Society of Cardiology Committee for Practice Guidelines (Writing Committee to Develop Guidelines for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death).
The purpose this document is to update and combine the previously
published recommendations into one source approved by
the major cardiology organizations in the United States and
Europe. We have consciously attempted to create a streamlined
document, not a textbook, that would be useful
specifically to locate recommendations on the evaluation
and treatment of patients who have or may be at risk for
ventricular arrhythmias. Thus, sections on epidemiology,
mechanisms and substrates, and clinical presentations are
brief, because there are no recommendations for those
sections. For the other sections, the wording has been kept
to a minimum, and clinical presentations have been confined
to those aspects relevant to forming recommendations