keywords:
EXACT-SECOND-DERIVATIVES-USED
BFGS-APPROXIMATION-USED
DFP-APPROXIMATION-USED
PSB-APPROXIMATION-USED
SR1-APPROXIMATION-USED
The user is frequently able to provide analytic expressions for the
first derivatives
of the nonlinear element functions in the SEIF file.
The specification of exact second derivatives is optional, but
recommended whenever possible.
If exact second derivatives have been supplied, the
keyword EXACT-SECOND-DERIVATIVES-USED should be included. In their
absence four different second derivative approximations may be used.
These are the Broyden-Fletcher-Goldfarb-Shanno (BFGS),
Davidon-Fletcher-Powell (DFP), Powell-symmetric-Broyden (PSB) and
symmetric rank-one (SR1) approximations which may be invoked using the
BFGS-APPROXIMATION-USED,
DFP-APPROXIMATION-USED,
PSB-APPROXIMATION-USED and
SR1-APPROXIMATION-USED
keywords, respectively. A default of