| [fcn,jac,iopt,n,x,fvec,tol,nprint,info,wa,lwa]=snsqe(fcn,jac,iopt,n,x,fvec,tol,nprint,info,wa,lwa); |
function [fcn,jac,iopt,n,x,fvec,tol,nprint,info,wa,lwa]=snsqe(fcn,jac,iopt,n,x,fvec,tol,nprint,info,wa,lwa);
%***BEGIN PROLOGUE SNSQE
%***PURPOSE An easy-to-use code to find a zero of a system of N
% nonlinear functions in N variables by a modification of
% the Powell hybrid method.
%***LIBRARY SLATEC
%***CATEGORY F2A
%***TYPE SINGLE PRECISION (SNSQE-S, DNSQE-D)
%***KEYWORDS EASY-TO-USE, NONLINEAR SQUARE SYSTEM,
% POWELL HYBRID METHOD, ZEROS
%***AUTHOR Hiebert, K. L., (SNLA)
%***DESCRIPTION
%
% 1. Purpose.
%
%
% The purpose of SNSQE is to find a zero of a system of N non-
% linear functions in N variables by a modification of the Powell
% hybrid method. This is done by using the more general nonlinear
% equation solver SNSQ. The user must provide a subroutine which
% calculates the functions. The user has the option of either to
% provide a subroutine which calculates the Jacobian or to let the
% code calculate it by a forward-difference approximation. This
% code is the combination of the MINPACK codes (Argonne) HYBRD1
% and HYBRJ1.
%
%
% 2. subroutine and Type Statements.
%
% subroutine SNSQE(FCN,JAC,IOPT,N,X,FVEC,TOL,NPRINT,INFO,
% * WA,LWA)
% INTEGER IOPT,N,NPRINT,INFO,LWA
% REAL TOL
% REAL X(N),FVEC(N),WA(LWA)
% EXTERNAL FCN,JAC
%
%
% 3. Parameters.
%
% Parameters designated as input parameters must be specified on
% entry to SNSQE and are not changed on exit, while parameters
% designated as output parameters need not be specified on entry
% and are set to appropriate values on exit from SNSQE.
%
% 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(N,X,FVEC,IFLAG)
% INTEGER N,IFLAG
% REAL X(N),FVEC(N)
% ----------
% 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 SNSQE. In this case, set
% IFLAG to a negative integer.
%
% JAC is the name of the user-supplied subroutine which calculates
% the Jacobian. If IOPT=1, then JAC must be declared in an
% EXTERNAL statement in the user calling program, and should be
% written as follows.
%
% subroutine JAC(N,X,FVEC,FJAC,LDFJAC,IFLAG)
% INTEGER N,LDFJAC,IFLAG
% REAL X(N),FVEC(N),FJAC(LDFJAC,N)
% ----------
% Calculate the Jacobian at X and return this
% matrix in FJAC. FVEC contains the function
% values at X and should not be altered.
% ----------
% RETURN
% end
%
% The value of IFLAG should not be changed by JAC unless the
% user wants to terminate execution of SNSQE. In this case, set
% IFLAG to a negative integer.
%
% If IOPT=2, JAC can be ignored (treat it as a dummy argument).
%
% IOPT is an input variable which specifies how the Jacobian will
% be calculated. If IOPT=1, then the user must supply the
% Jacobian through the subroutine JAC. If IOPT=2, then the
% code will approximate the Jacobian by forward-differencing.
%
% N is a positive integer input variable set to the number of
% functions and variables.
%
% X is an array of length N. On input, X must contain an initial
% estimate of the solution vector. On output, X contains the
% final estimate of the solution vector.
%
% FVEC is an output array of length N which contains the functions
% evaluated at the output X.
%
% TOL is a non-negative input variable. Termination occurs when
% the algorithm estimates that the relative error between X and
% the solution is at most TOL. Section 4 contains more details
% about TOL.
%
% NPRINT is an integer input variable that enables controlled
% printing of iterates if it is positive. In this case, FCN is
% called with IFLAG = 0 at the beginning of the first iteration
% and every NPRINT iteration thereafter and immediately prior
% to return, with X and FVEC available for printing. Appropriate
% print statements must be added to FCN (see example). If NPRINT
% is not positive, no special calls of FCN with IFLAG = 0 are
% made.
%
% INFO is an integer output variable. If the user has terminated
% execution, INFO is set to the (negative) value of IFLAG. See
% description of FCN and JAC. Otherwise, INFO is set as follows.
%
% INFO = 0 improper input parameters.
%
% INFO = 1 algorithm estimates that the relative error between
% X and the solution is at most TOL.
%
% INFO = 2 number of calls to FCN has reached or exceeded
% 100*(N+1) for IOPT=1 or 200*(N+1) for IOPT=2.
%
% INFO = 3 TOL is too small. No further improvement in the
% approximate solution X is possible.
%
% INFO = 4 iteration is not making good progress.
%
% Sections 4 and 5 contain more details about INFO.
%
% WA is a work array of length LWA.
%
% LWA is a positive integer input variable not less than
% (3*N**2+13*N))/2.
%
%
% 4. Successful Completion.
%
% The accuracy of SNSQE is controlled by the convergence parame-
% ter TOL. This parameter is used in a test which makes a compar-
% ison between the approximation X and a solution XSOL. SNSQE
% terminates when the test is satisfied. If TOL is less than the
% machine precision (as defined by the function R1MACH(4)), then
% SNSQE attempts only to satisfy the test defined by the machine
% precision. Further progress is not usually possible. Unless
% high precision solutions are required, the recommended value
% for TOL is the square root of the machine precision.
%
% The test assumes that the functions are reasonably well behaved,
% and, if the Jacobian is supplied by the user, that the functions
% and the Jacobian coded consistently. If these conditions
% are not satisfied, SNSQE may incorrectly indicate convergence.
% The coding of the Jacobian can be checked by the subroutine
% CHKDER. If the Jacobian is coded correctly or IOPT=2, then
% the validity of the answer can be checked, for example, by
% rerunning SNSQE with a tighter tolerance.
%
% Convergence Test. If ENORM(Z) denotes the Euclidean norm of a
% vector Z, then this test attempts to guarantee that
%
% ENORM(X-XSOL) .LE. TOL*ENORM(XSOL).
%
% If this condition is satisfied with TOL = 10**(-K), then the
% larger components of X have K significant decimal digits and
% INFO is set to 1. There is a danger that the smaller compo-
% nents of X may have large relative errors, but the fast rate
% of convergence of SNSQE usually avoids this possibility.
%
%
% 5. Unsuccessful Completion.
%
% Unsuccessful termination of SNSQE can be due to improper input
% parameters, arithmetic interrupts, an excessive number of func-
% tion evaluations, errors in the functions, or lack of good prog-
% ress.
%
% Improper Input Parameters. INFO is set to 0 if IOPT .LT. 1, or
% IOPT .GT. 2, or N .LE. 0, or TOL .LT. 0.0E0, or
% LWA .LT. (3*N**2+13*N)/2.
%
% Arithmetic Interrupts. If these interrupts occur in the FCN
% subroutine during an early stage of the computation, they may
% be caused by an unacceptable choice of X by SNSQE. In this
% case, it may be possible to remedy the situation by not evalu-
% ating the functions here, but instead setting the components
% of FVEC to numbers that exceed those in the initial FVEC.
%
% Excessive Number of Function Evaluations. If the number of
% calls to FCN reaches 100*(N+1) for IOPT=1 or 200*(N+1) for
% IOPT=2, then this indicates that the routine is converging
% very slowly as measured by the progress of FVEC, and INFO is
% set to 2. This situation should be unusual because, as
% indicated below, lack of good progress is usually diagnosed
% earlier by SNSQE, causing termination with INFO = 4.
%
% Errors in the Functions. When IOPT=2, the choice of step length
% in the forward-difference approximation to the Jacobian
% assumes that the relative errors in the functions are of the
% order of the machine precision. If this is not the case,
% SNSQE may fail (usually with INFO = 4). The user should
% then either use SNSQ and set the step length or use IOPT=1
% and supply the Jacobian.
%
% Lack of Good Progress. SNSQE searches for a zero of the system
% by minimizing the sum of the squares of the functions. In so
% doing, it can become trapped in a region where the minimum
% does not correspond to a zero of the system and, in this situ-
% ation, the iteration eventually fails to make good progress.
% In particular, this will happen if the system does not have a
% zero. If the system has a zero, rerunning SNSQE from a dif-
% ferent starting point may be helpful.
%
%
% 6. Characteristics of the Algorithm.
%
% SNSQE is a modification of the Powell hybrid method. Two of
% its main characteristics involve the choice of the correction as
% a convex combination of the Newton and scaled gradient direc-
% tions, and the updating of the Jacobian by the rank-1 method of
% Broyden. The choice of the correction guarantees (under reason-
% able conditions) global convergence for starting points far from
% the solution and a fast rate of convergence. The Jacobian is
% calculated at the starting point by either the user-supplied
% subroutine or a forward-difference approximation, but it is not
% recalculated until the rank-1 method fails to produce satis-
% factory progress.
%
% Timing. The time required by SNSQE to solve a given problem
% depends on N, the behavior of the functions, the accuracy
% requested, and the starting point. The number of arithmetic
% operations needed by SNSQE is about 11.5*(N**2) to process
% each evaluation of the functions (call to FCN) and 1.3*(N**3)
% to process each evaluation of the Jacobian (call to JAC,
% if IOPT = 1). Unless FCN and JAC can be evaluated quickly,
% the timing of SNSQE will be strongly influenced by the time
% spent in FCN and JAC.
%
% Storage. SNSQE requires (3*N**2 + 17*N)/2 single precision
% storage locations, in addition to the storage required by the
% program. There are no internally declared storage arrays.
%
%
% 7. Example.
%
% The problem is to determine the values of X(1), X(2), ..., X(9),
% which solve the system of tridiagonal equations
%
% (3-2*X(1))*X(1) -2*X(2) = -1
% -X(I-1) + (3-2*X(I))*X(I) -2*X(I+1) = -1, I=2-8
% -X(8) + (3-2*X(9))*X(9) = -1
%
% **********
%
% program TEST
% C
% C Driver for SNSQE example.
% C
% INTEGER J,N,IOPT,NPRINT,INFO,LWA,NWRITE
% REAL TOL,FNORM
% REAL X(9),FVEC(9),WA(180)
% REAL ENORM,R1MACH
% EXTERNAL FCN
% DATA NWRITE /6/
% C
% IOPT = 2
% N = 9
% C
% C The following starting values provide a rough solution.
% C
% DO 10 J = 1, 9
% X(J) = -1.0E0
% 10 CONTINUE
%
% LWA = 180
% NPRINT = 0
% C
% C Set TOL to the square root of the machine precision.
% C Unless high precision solutions are required,
% C this is the recommended setting.
% C
% TOL = SQRT(R1MACH(4))
% C
% CALL SNSQE(FCN,JAC,IOPT,N,X,FVEC,TOL,NPRINT,INFO,WA,LWA)
% FNORM = ENORM(N,FVEC)
% WRITE (NWRITE,1000) FNORM,INFO,(X(J),J=1,N)
% STOP
% 1000 FORMAT (5X,' FINAL L2 NORM OF THE RESIDUALS',E15.7 //
% * 5X,' EXIT PARAMETER',16X,I10 //
% * 5X,' FINAL APPROXIMATE SOLUTION' // (5X,3E15.7))
% end
% subroutine FCN(N,X,FVEC,IFLAG)
% INTEGER N,IFLAG
% REAL X(N),FVEC(N)
% INTEGER K
% REAL ONE,TEMP,TEMP1,TEMP2,THREE,TWO,ZERO
% DATA ZERO,ONE,TWO,THREE /0.0E0,1.0E0,2.0E0,3.0E0/
% C
% DO 10 K = 1, N
% TEMP = (THREE - TWO*X(K))*X(K)
% TEMP1 = ZERO
% IF (K .NE. 1) TEMP1 = X(K-1)
% TEMP2 = ZERO
% IF (K .NE. N) TEMP2 = X(K+1)
% FVEC(K) = TEMP - TEMP1 - TWO*TEMP2 + ONE
% 10 CONTINUE
% RETURN
% end
%
% Results obtained with different compilers or machines
% may be slightly different.
%
% FINAL L2 NORM OF THE RESIDUALS 0.1192636E-07
%
% EXIT PARAMETER 1
%
% FINAL APPROXIMATE SOLUTION
%
% -0.5706545E+00 -0.6816283E+00 -0.7017325E+00
% -0.7042129E+00 -0.7013690E+00 -0.6918656E+00
% -0.6657920E+00 -0.5960342E+00 -0.4164121E+00
%
%***REFERENCES M. J. D. Powell, A hybrid method for nonlinear equa-
% tions. In Numerical Methods for Nonlinear Algebraic
% Equations, P. Rabinowitz, Editor. Gordon and Breach,
% 1988.
%***ROUTINES CALLED SNSQ, XERMSG
%***REVISION HISTORY (YYMMDD)
% 800301 DATE WRITTEN
% 890831 Modified array declarations. (WRB)
% 890831 REVISION DATE from Version 3.2
% 891214 Prologue converted to Version 4.0 format. (BAB)
% 900315 CALLs to XERROR changed to CALLs to XERMSG. (THJ)
% 920501 Reformatted the REFERENCES section. (WRB)
%***end PROLOGUE SNSQE
persistent epsfcn factor firstCall indexmlv j lr maxfev ml mode mu nfev njev one xtol zero ; if isempty(firstCall),firstCall=1;end;
x_shape=size(x);x=reshape(x,1,[]);
fvec_shape=size(fvec);fvec=reshape(fvec,1,[]);
if isempty(indexmlv), indexmlv=0; end;
if isempty(j), j=0; end;
if isempty(lr), lr=0; end;
if isempty(maxfev), maxfev=0; end;
if isempty(ml), ml=0; end;
if isempty(mode), mode=0; end;
if isempty(mu), mu=0; end;
if isempty(nfev), nfev=0; end;
if isempty(njev), njev=0; end;
if isempty(epsfcn), epsfcn=0; end;
if isempty(factor), factor=0; end;
if isempty(one), one=0; end;
if isempty(xtol), xtol=0; end;
if isempty(zero), zero=0; end;
if firstCall, factor =[1.0e2]; end;
if firstCall, one =[1.0e0]; end;
if firstCall, zero=[0.0e0]; end;
firstCall=0;
%***FIRST EXECUTABLE STATEMENT SNSQE
info = 0;
%
% CHECK THE INPUT PARAMETERS FOR ERRORS.
%
if( iopt>=1 && iopt<=2 && n>0 && tol>=zero &&lwa>=fix(((3.*n).^2+(13.*n))./2) )
%
% CALL SNSQ.
%
maxfev = fix(100.*(n+1));
if( iopt==2 )
maxfev = fix(2.*maxfev);
end;
xtol = tol;
ml = fix(n - 1);
mu = fix(n - 1);
epsfcn = zero;
mode = 2;
for j = 1 : n;
wa(j) = one;
end; j = fix(n+1);
lr =fix(fix((n.*(n+1))./2));
indexmlv = 6.*n + lr;
n_orig=n; [fcn,jac,iopt,n,x,fvec,dumvar7,dumvar8,xtol,maxfev,ml,mu,epsfcn,dumvar14,mode,factor,nprint,info,nfev,njev,dumvar21,lr,dumvar23,dumvar24,dumvar25,dumvar26,wa(5.*n+1)]=snsq(fcn,jac,iopt,n,x,fvec,wa(indexmlv+1),n,xtol,maxfev,ml,mu,epsfcn,wa(1),mode,factor,nprint,info,nfev,njev,wa(6.*n+1),lr,wa(sub2ind(size(wa),max(n+1,1)):end),wa(sub2ind(size(wa),max(2.*n+1,1)):end),wa(sub2ind(size(wa),max(3.*n+1,1)):end),wa(sub2ind(size(wa),max(4.*n+1,1)):end),wa(5.*n+1)); n(dumvar8~=n_orig)=dumvar8(dumvar8~=n_orig); dumvar7i=find((wa(indexmlv+1))~=(dumvar7));dumvar14i=find((wa(1))~=(dumvar14));dumvar21i=find((wa(6.*n+1))~=(dumvar21));dumvar23i=find((wa(sub2ind(size(wa),max(n+1,1)):end))~=(dumvar23));dumvar24i=find((wa(sub2ind(size(wa),max(2.*n+1,1)):end))~=(dumvar24));dumvar25i=find((wa(sub2ind(size(wa),max(3.*n+1,1)):end))~=(dumvar25));dumvar26i=find((wa(sub2ind(size(wa),max(4.*n+1,1)):end))~=(dumvar26)); wa(indexmlv+1-1+dumvar7i)=dumvar7(dumvar7i); wa(1-1+dumvar14i)=dumvar14(dumvar14i); wa(6.*n+1-1+dumvar21i)=dumvar21(dumvar21i); wa(n+1-1+dumvar23i)=dumvar23(dumvar23i); wa(2.*n+1-1+dumvar24i)=dumvar24(dumvar24i); wa(3.*n+1-1+dumvar25i)=dumvar25(dumvar25i); wa(4.*n+1-1+dumvar26i)=dumvar26(dumvar26i);
if( info==5 )
info = 4;
end;
end;
if( info==0 )
xermsg('SLATEC','SNSQE','INVALID INPUT PARAMETER.',2,1);
end;
%
% LAST CARD OF SUBROUTINE SNSQE.
%
x_shape=zeros(x_shape);x_shape(:)=x(1:numel(x_shape));x=x_shape;
fvec_shape=zeros(fvec_shape);fvec_shape(:)=fvec(1:numel(fvec_shape));fvec=fvec_shape;
end
%DECK SNSQ
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