[u/mrichter/AliRoot.git] / GEANT321 / gstrag / gxgint.F

*
* $Id$
*
* $Log$
* Revision 1.1.1.1  1995/10/24 10:21:39  cernlib
* Geant
*
*
#include "geant321/pilot.h"
*CMZ :  3.21/02 29/03/94  15.41.25  by  S.Giani
*-- Author :
      FUNCTION GXGINT(EXT,A,B,EPS)
*
*    Gauss integration routine
*
#include "geant321/gcunit.inc"
#if !defined(CERNLIB_SINGLE)
      DOUBLE PRECISION OTB,U1,U2,W1,W2,Y
#endif
      EXTERNAL EXT
      PARAMETER (U1=.3399810,U2=.8611363,W1=.6521452,W2=.3478548)
*
*-----------------------------------------------------------------------
*
      N      = 5
      OTB    = 0
      DHALF  = (B-A)/N
   10 CONTINUE
*
*   Convergence loop
*
      Y = OTB
      OTB = 0
      D = DHALF
      DHALF = 0.5*D
      CENTX = A-DHALF
      D1 = U1*DHALF
      D2 = U2*DHALF
*
*   Piecewise integration loop
*
      DO 20 I=1,N
         CENTX=CENTX+D
         OTB = OTB +W2*(EXT(CENTX-D2)+EXT(CENTX+D2)) +W1*(EXT(CENTX-D1)
     +   +EXT(CENTX+D1))
   20 CONTINUE
      OTB=OTB*DHALF
*
      IF(EPS.GT.0.AND.ABS(OTB-Y).GT.ABS(EPS*OTB)) THEN
         N = 2*N
         IF (N.GT.100 000) THEN
*
*   Check N>100 000
*
            WRITE(CHMAIL,10000) EPS, ABS((OTB-Y)/OTB)
            CALL GMAIL(1,0)
            GO TO 30
         END IF
         GOTO 10
      ENDIF
*
   30 CONTINUE
      GXGINT=OTB
10000 FORMAT('*** GXGINT : required precision ',G10.3,
     +      ' obtained precision ',G10.3)
      END
Commit	Line	Data
fe4da5cc	1	*
	2	* $Id$
	3	*
	4	* $Log$
	5	* Revision 1.1.1.1 1995/10/24 10:21:39 cernlib
	6	* Geant
	7	*
	8	*
	9	#include "geant321/pilot.h"
	10	*CMZ : 3.21/02 29/03/94 15.41.25 by S.Giani
	11	*-- Author :
	12	FUNCTION GXGINT(EXT,A,B,EPS)
	13	*
	14	* Gauss integration routine
	15	*
	16	#include "geant321/gcunit.inc"
	17	#if !defined(CERNLIB_SINGLE)
	18	DOUBLE PRECISION OTB,U1,U2,W1,W2,Y
	19	#endif
	20	EXTERNAL EXT
	21	PARAMETER (U1=.3399810,U2=.8611363,W1=.6521452,W2=.3478548)
	22	*
	23	*-----------------------------------------------------------------------
	24	*
	25	N = 5
	26	OTB = 0
	27	DHALF = (B-A)/N
	28	10 CONTINUE
	29	*
	30	* Convergence loop
	31	*
	32	Y = OTB
	33	OTB = 0
	34	D = DHALF
	35	DHALF = 0.5*D
	36	CENTX = A-DHALF
	37	D1 = U1*DHALF
	38	D2 = U2*DHALF
	39	*
	40	* Piecewise integration loop
	41	*
	42	DO 20 I=1,N
	43	CENTX=CENTX+D
	44	OTB = OTB +W2(EXT(CENTX-D2)+EXT(CENTX+D2)) +W1(EXT(CENTX-D1)
	45	+ +EXT(CENTX+D1))
	46	20 CONTINUE
	47	OTB=OTB*DHALF
	48	*
	49	IF(EPS.GT.0.AND.ABS(OTB-Y).GT.ABS(EPS*OTB)) THEN
	50	N = 2*N
	51	IF (N.GT.100 000) THEN
	52	*
	53	* Check N>100 000
	54	*
	55	WRITE(CHMAIL,10000) EPS, ABS((OTB-Y)/OTB)
	56	CALL GMAIL(1,0)
	57	GO TO 30
	58	END IF
	59	GOTO 10
	60	ENDIF
	61	*
	62	30 CONTINUE
	63	GXGINT=OTB
	64	10000 FORMAT('*** GXGINT : required precision ',G10.3,
65	+ ' obtained precision ',G10.3)
66	END