Double: The double precision function name is DGPIRG.
Description
Let M = NEVAL, xj = EVEC(*,J) , the j-th column of EVEC. Also, let ɛ be the machine precision given by AMACH(4), see the Reference chapter of this manual. The performance index, , is defined to be
The norms used are a modified form of the 1-norm. The norm of the complex vector v is
While the exact value of is highly machine dependent, the performance of GVCRG is considered excellent if < 1, good if 1 ≤≤ 100, and poor if > 100. The performance index was first developed by the EISPACK project at Argonne National Laboratory; see Garbow et al. (1977, pages 77− 79).
Comments
1. Workspace may be explicitly provided, if desired, by use of G2IRG/DG2IRG. The reference is: