dfpmin.dem

	PROGRAM D10R11
C	Driver for routine DFPMIN
	PARAMETER(NDIM=3,FTOL=1.0E-6,PIO2=1.5707963)
	DIMENSION P(NDIM)
	WRITE(*,'(/1X,A)') 'Program finds the minimum of a function'
	WRITE(*,'(1X,A)') 'with different trial starting vectors.'
	WRITE(*,'(1X,A)') 'True minimum is (0.5,0.5,0.5)'
	DO 11 K=0,4
		ANGL=PIO2*K/4.0
		P(1)=2.0*COS(ANGL)
		P(2)=2.0*SIN(ANGL)
		P(3)=0.0
		WRITE(*,'(/1X,A,3(F6.4,A))') 'Starting vector: (',
     *			P(1),',',P(2),',',P(3),')'
		CALL DFPMIN(P,NDIM,FTOL,ITER,FRET)
		WRITE(*,'(1X,A,I3)') 'Iterations:',ITER
		WRITE(*,'(1X,A,3(F6.4,A))') 'Solution vector: (',
     *			P(1),',',P(2),',',P(3),')'
		WRITE(*,'(1X,A,E14.6)') 'Func. value at solution',FRET
11	CONTINUE
	END

	FUNCTION FUNC(X)
	DIMENSION X(3)
	FUNC=1.0-BESSJ0(X(1)-0.5)*BESSJ0(X(2)-0.5)*BESSJ0(X(3)-0.5)
	END

	SUBROUTINE DFUNC(X,DF)
	PARAMETER (NMAX=50)
	DIMENSION X(3),DF(NMAX)
	DF(1)=BESSJ1(X(1)-0.5)*BESSJ0(X(2)-0.5)*BESSJ0(X(3)-0.5)
	DF(2)=BESSJ0(X(1)-0.5)*BESSJ1(X(2)-0.5)*BESSJ0(X(3)-0.5)
	DF(3)=BESSJ0(X(1)-0.5)*BESSJ0(X(2)-0.5)*BESSJ1(X(3)-0.5)
	RETURN
	END