The orthogonalization method used for the Arnoldi procedure.
Only for TDExponentialMethod = lanczos.
Options:
cgs:
Classical Gram-Schmidt (CGS) orthogonalization.
The algorithm is defined in Giraud et al., Computers and Mathematics with Applications 50, 1069 (2005).
drcgs:
Classical Gram-Schmidt orthogonalization with double-step reorthogonalization.
The algorithm is taken from Giraud et al., Computers and Mathematics with Applications 50, 1069 (2005).
According to this reference, this is much more precise than CGS or MGS algorithms.