FDJAC3(3)

SYNOPSIS
SUBROUTINE FDJAC3 (FCN, M, N, X, FVEC, FJAC, LDFJAC, IFLAG, + EPSFCN, WA)

NAME
fdjac3 - Subsidiary to SNLS1 and SNLS1E

LIBRARY
SLATEC

TYPE
SINGLE PRECISION (FDJAC3-S, DFDJC3-D)

AUTHOR
(UNKNOWN)

DESCRIPTION
This subroutine computes a forward-difference approximation to the M by N Jacobian matrix associated with a specified problem of M functions in N variables. The subroutine statement is SUBROUTINE FDJAC3(FCN,M,N,X,FVEC,FJAC,LDFJAC,IFLAG,EPSFCN,WA) where FCN is the name of the user-supplied subroutine which calculates the functions. FCN must be declared in an external statement in the user calling program, and should be written as follows. SUBROUTINE FCN(IFLAG,M,N,X,FVEC,FJAC,LDFJAC) INTEGER LDFJAC,M,N,IFLAG REAL X(N),FVEC(M),FJAC(LDFJAC,N) ---------- When IFLAG.EQ.1 calculate the functions at X and return this vector in FVEC. ---------- RETURN END The value of IFLAG should not be changed by FCN unless the user wants to terminate execution of FDJAC3. In this case set IFLAG to a negative integer. M is a positive integer input variable set to the number of functions. N is a positive integer input variable set to the number of variables. N must not exceed M. X is an input array of length N. FVEC is an input array of length M which must contain the functions evaluated at X. FJAC is an output M by N array which contains the approximation to the Jacobian matrix evaluated at X. LDFJAC is a positive integer input variable not less than M which specifies the leading dimension of the array FJAC. IFLAG is an integer variable which can be used to terminate THE EXECUTION OF FDJAC3. See description of FCN. EPSFCN is an input variable used in determining a suitable step length for the forward-difference approximation. This approximation assumes that the relative errors in the functions are of the order of EPSFCN. If EPSFCN is less than the machine precision, it is assumed that the relative errors in the functions are of the order of the machine precision. WA is a work array of length M.

SEE ALSO
SNLS1, SNLS1E

ROUTINES CALLED
R1MACH

REVISION HISTORY (YYMMDD)
800301 DATE WRITTEN
890531 Changed all specific intrinsics to generic. (WRB)
890831 Modified array declarations. (WRB)
891214 Prologue converted to Version 4.0 format. (BAB)
900326 Removed duplicate information from DESCRIPTION section. (WRB)
900328 Added TYPE section. (WRB)