Poster: The performance of derivative code generated by TAMC
by
Ralf Giering
Jet-Propulsion-Laboratory
Coauthors: Thomas Kaminski (Max-Planck-Institut fuer Meteorologie, Hamburg)

The Tangent linear and Adjoint Model Compiler (TAMC) is a source-to-source translator for Fortran programs that generates code to evaluate first order derivatives. The performance of TAMC generated adjoint and second order derivative code is compared to that of hand coded counterparts for scalar valued functions in the Minpack-2 collection. In general the run times for the automatically generated and hand written codes are similar. The performance depends mainly on architecture and compiler characteristics. Only in one case is the TAMC generated code significantly faster than the hand written code. This is because the major loop was split up in the Minpack-2 code to handle the boundaries of a 2-dimensional domain differently. This common practice in hand coded adjoints decreases performance. Adjoint models for large scale applications in dynamic meteorology and oceanography have been generated by TAMC. For some of the largest examples, the performance is discussed. All of these examples use automatically generated (2- or 3-level) checkpointing schemes to provide the required values efficiently. Including the cost of this checkpointing, the run time of the adjoint code still is no more than about a factor of 3 to 6 larger than that of the respective function evaluation.

http://puddle.mit.edu/~ralf/tamc

Date received: December 30, 1999