SECTION 4.

POWELL

For description of algorithm see M.J.D.Powell, An Efficient
Method for Finding the Minimum of a Function of Several Variables
Without Calculating Derivatives, *Computer Journal*,
7(1964),155-62

STORAGE REQUIREMENTS

NQ = i2 = 2*NP + NP*NP

TERMINATION FLAGS

IER = Greater than 0 if optimum is achieved

IER = 3 Function value is accurate to relative ACC

IER = 1 Attempted step size is less than ACC (relatively)

IER = -1 Iteration limit exceeded

IER = -3 Input error

IER = -4 Not enough scratch storage

IER = -9 Function error in first FUNC call

IER =-13 No stopping criterion enabled

Besides the general options the following are available. The option which will most likely be of interest to the user is STEP1.

COMMON/BLNSR/STEP1,STPACC,NLNSR

STEP1 = Length of the initial step taken bySTR in linear
optimizing. Default = 1

STPACC = Accuracy required in linear optimizing. Default is
ACC/NP

NLNSR = Maximum number of steps in each linear search. Default =
20