Restructuring the BLAS Level 1 Routine for Computing the Modified Givens Transformation

We look at how both logical restructuring and improvements available from successive versions of Fortran allow us to reduce the complexity (measured by a number of the commonly used software metrics) of the Level 1 BLAS code used to compute the modified Givens transformation. With these reductions in complexity we claim that we have improved both the maintainability and clarity of the code; in addition, we report a fix to a minor problem with the original code. The performance of two commercial Fortran restructuring tools is also reported. 1 Introduction The Level 1 BLAS [LHKK79], originally published in Fortran 66 [ANS66], implemented a number of common vector operations and were designed to be used as building blocks for linear algebra software. Hopkins [Hop96] used knot counts [WHH79] and path counts [Nej88] to identify routines from the Level 1 BLAS which might benefit from code restructuring Two sets of routines, *NRM2, used to compute the Euclidean norm of a vector and *ROTMG, f..