dbrent.dem

	PROGRAM D10R4
C	Driver for routine DBRENT
	PARAMETER(TOL=1.0E-6,EQL=1.E-4)
	EXTERNAL BESSJ0,DERIV
	DIMENSION AMIN(20)
	NMIN=0
	WRITE(*,'(/1X,A)') 'Minima of the function BESSJ0'
	WRITE(*,'(/1X,T6,A,T19,A,T27,A,T39,A,T53,A/)') 'Min. #','X',
     *		'BESSJ0(X)','BESSJ1(X)','DBRENT'
	DO 12 I=1,100
		AX=I
		BX=I+1.0
		CALL MNBRAK(AX,BX,CX,FA,FB,FC,BESSJ0)
		DBR=DBRENT(AX,BX,CX,BESSJ0,DERIV,TOL,XMIN)
		IF (NMIN.EQ.0) THEN
			AMIN(1)=XMIN
			NMIN=1
			WRITE(*,'(1X,5X,I2,3X,4F12.6)') NMIN,XMIN,
     *				BESSJ0(XMIN),DERIV(XMIN),DBR
		ELSE
			IFLAG=0
			DO 11 J=1,NMIN
				IF (ABS(XMIN-AMIN(J)).LE.EQL*XMIN) IFLAG=1
11			CONTINUE
			IF (IFLAG.EQ.0) THEN
				NMIN=NMIN+1
				AMIN(NMIN)=XMIN
				WRITE(*,'(1X,5X,I2,3X,4F12.6)') NMIN,XMIN,
     *					BESSJ0(XMIN),DERIV(XMIN),DBR
			ENDIF
		ENDIF
12	CONTINUE
	END

	FUNCTION DERIV(X)
	DERIV=-BESSJ1(X)
	END