tr-announce March 2007

tr-announce@lists.rwth-aachen.de

1 participants
2 discussions

2007-05: On Optimal DAG Reversal

by Peter Schneider-Kamp

The following technical report is available from http://aib.informatik.rwth-aachen.de: On Optimal DAG Reversal Uwe Naumann AIB 2007-05 Runs of numerical computer programs can be visualized as directed acyclic graphs (DAGs). We consider the problem of restoring the intermediate values computed by such a program (the vertices in the DAG) in reverse order for a given upper bound on the available memory. The minimization of the associated computational cost in terms of the number of performed arithmetic operations is shown to be NP-complete. The reversal of the data-flow finds application, for example, in the efficient evaluation of adjoint numerical programs. We derive special cases of numerical programs that require the intermediate values exactly in reverse order, thus establishing the NP-completeness of the optimal adjoint computation problem. Last but not least we review some state-of-theart approaches to efficient data-flow reversal taken by existing software tools for automatic differentiation.

17 years, 5 months

2007-04: coJIVE: A System to Support Collaborative Jazz Improvisation

by Peter Schneider-Kamp

The following technical report is available from http://aib.informatik.rwth-aachen.de: coJIVE: A System to Support Collaborative Jazz Improvisation Jan Buchholz, Eric Lee, Jonathan Klein, and Jan Borchers AIB 2007-04 Jazz improvisation is a complex and demanding art of on-the-fly composition and performance. We present coJIVE, a system that allows musically inexperienced people to improvise to jazz by substituting for musical knowledge and experience. Using well-established musical theory, it aids users in creating a harmonic performance, and also helps coordinate a collaborative session amongst the participants. Remarks from users during evaluation showed an overall positive response to the support provided by the system.

17 years, 6 months

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tr-announce March 2007