Algorithm 830

Algorithm 830: Another visit with standard and modified Givens transformations and a remark on algorithm 539 First we report on a correction and improvement to the Level 1 BLAS routine srotmg for computing the Modified Givens Transformation (MG). We then, in the light of the performance of the code on modern compiler/hardware combinations, reconsider the strategy of supplying separate routines to compute and apply the transformation. Finally, we show that the apparent savings in multiplies obtained by using MG rather than the Standard Givens Transformation (SG) do not always translate into reductions in execution time. (Source:

This software is also peer reviewed by journal TOMS.