#include "isajet/pilot.h"
      DOUBLE PRECISION FUNCTION SSDINT(XL,F,XR)
C-----------------------------------------------------------------------
C          Integrate F over (XL,XR) using adaptive Gaussian quadrature.
C          TOLABS = 1e-35: absolute error for convergence.
C          TOLREL = 5e-5:  relative error for convergence.
C          TOLBIN = 1e-3:  relative bin size limit. Set contribution to
C                          zero if bin falls below this.
C     Note quadrature constants R and W have been converted to explicit
C     double precision (.xxxxxDxx) form.
C
C     Bisset's XINTH     
C-----------------------------------------------------------------------
#if defined(CERNLIB_IMPNONE)
      IMPLICIT NONE
#endif
#include "isajet/sslun.inc"
      EXTERNAL F
      INTEGER NMAX
      DOUBLE PRECISION TOLABS,TOLREL,TOLBIN,XMIN,XLIMS(100)
      DOUBLE PRECISION R(93),W(93)
      INTEGER PTR(4),NORD(4)
      INTEGER ICOUNT,IBAD
      DOUBLE PRECISION XL,XR,F
      DOUBLE PRECISION AA,BB,TVAL,VAL,TOL
      INTEGER NLIMS,I,J,KKK
C
      DATA PTR,NORD/4,10,22,46,  6,12,24,48/
      DATA (R(KKK),KKK=1,48)/
     $ .2386191860D0,.6612093865D0,.9324695142D0,.1252334085D0,
     $ .3678314990D0,.5873179543D0,.7699026742D0,.9041172563D0,
     $ .9815606342D0,.0640568929D0,.1911188675D0,.3150426797D0,
     $ .4337935076D0,.5454214714D0,.6480936519D0,.7401241916D0,
     $ .8200019860D0,.8864155270D0,.9382745520D0,.9747285560D0,
     $ .9951872200D0,.0323801710D0,.0970046992D0,.1612223561D0,
     $ .2247637903D0,.2873624873D0,.3487558863D0,.4086864820D0,
     $ .4669029048D0,.5231609747D0,.5772247261D0,.6288673968D0,
     $ .6778723796D0,.7240341309D0,.7671590325D0,.8070662040D0,
     $ .8435882616D0,.8765720203D0,.9058791367D0,.9313866907D0,
     $ .9529877032D0,.9705915925D0,.9841245837D0,.9935301723D0,
     $ .9987710073D0,.0162767488D0,.0488129851D0,.0812974955D0/
      DATA (R(KKK),KKK=49,93)/
     $ .1136958501D0,.1459737146D0,.1780968824D0,.2100313105D0,
     $ .2417431561D0,.2731988126D0,.3043649444D0,.3352085229D0,
     $ .3656968614D0,.3957976498D0,.4254789884D0,.4547094222D0,
     $ .4834579739D0,.5116941772D0,.5393881083D0,.5665104186D0,
     $ .5930323648D0,.6189258401D0,.6441634037D0,.6687183100D0,
     $ .6925645366D0,.7156768123D0,.7380306437D0,.7596023411D0,
     $ .7803690438D0,.8003087441D0,.8194003107D0,.8376235112D0,
     $ .8549590334D0,.8713885059D0,.8868945174D0,.9014606353D0,
     $ .9150714231D0,.9277124567D0,.9393703398D0,.9500327178D0,
     $ .9596882914D0,.9683268285D0,.9759391746D0,.9825172636D0,
     $ .9880541263D0,.9925439003D0,.9959818430D0,.9983643759D0,
     $ .9996895039/
        DATA (W(KKK),KKK=1,48)/
     $ .4679139346D0,.3607615730D0,.1713244924D0,.2491470458D0,
     $ .2334925365D0,.2031674267D0,.1600783285D0,.1069393260D0,
     $ .0471753364D0,.1279381953D0,.1258374563D0,.1216704729D0,
     $ .1155056681D0,.1074442701D0,.0976186521D0,.0861901615D0,
     $ .0733464814D0,.0592985849D0,.0442774388D0,.0285313886D0,
     $ .0123412298D0,.0647376968D0,.0644661644D0,.0639242386D0,
     $ .0631141923D0,.0620394232D0,.0607044392D0,.0591148397D0,
     $ .0572772921D0,.0551995037D0,.0528901894D0,.0503590356D0,
     $ .0476166585D0,.0446745609D0,.0415450829D0,.0382413511D0,
     $ .0347772226D0,.0311672278D0,.0274265097D0,.0235707608D0,
     $ .0196161605D0,.0155793157D0,.0114772346D0,.0073275539D0,
     $ .0031533461D0,.0325506145D0,.0325161187D0,.0324471637D0/
      DATA (W(KKK),KKK=49,93)/
     $ .0323438226D0,.0322062048D0,.0320344562D0,.0318287589D0,
     $ .0315893308D0,.0313164256D0,.0310103326D0,.0306713761D0,
     $ .0302999154D0,.0298963441D0,.0294610900D0,.0289946142D0,
     $ .0284974111D0,.0279700076D0,.0274129627D0,.0268268667D0,
     $ .0262123407D0,.0255700360D0,.0249006332D0,.0242048418D0,
     $ .0234833991D0,.0227370697D0,.0219666444D0,.0211729399D0,
     $ .0203567972D0,.0195190811D0,.0186606796D0,.0177825023D0,
     $ .0168854799D0,.0159705629D0,.0150387210D0,.0140909418D0,
     $ .0131282296D0,.0121516047D0,.0111621020D0,.0101607705D0,
     $ .0091486712D0,.0081268769D0,.0070964708D0,.0060585455D0,
     $ .0050142027D0,.0039645543D0,.0029107318D0,.0018539608D0,
     $ .0007967921/
C
      DATA TOLABS,TOLREL,TOLBIN,NMAX/1.D-35,5.D-5,1D-5,100/
C
      SSDINT=0
      NLIMS=2
      XLIMS(1)=XL
      XLIMS(2)=XR
      ICOUNT=0
      IBAD=0
      XMIN=TOLBIN*ABS(XR-XL)
C
10    AA=(XLIMS(NLIMS)-XLIMS(NLIMS-1))/2
      BB=(XLIMS(NLIMS)+XLIMS(NLIMS-1))/2
      TVAL=0
      DO 15 I=1,3
15    TVAL=TVAL+W(I)*(F(BB+AA*R(I))+F(BB-AA*R(I)))
      TVAL=TVAL*AA
      DO 25 J=1,4
        VAL=0
        DO 20 I=PTR(J),PTR(J)-1+NORD(J)
          ICOUNT=ICOUNT+1
          IF(ICOUNT.GT.1E5) THEN
            WRITE(LOUT,*) 'ERROR IN SSDINT: SET SSDINT = 0'
            SSDINT=0.
            RETURN
          ENDIF
20      VAL=VAL+W(I)*(F(BB+AA*R(I))+F(BB-AA*R(I)))
        VAL=VAL*AA
        TOL=MAX(TOLABS,TOLREL*ABS(VAL))
        IF(ABS(TVAL-VAL).LT.TOL) THEN
          SSDINT=SSDINT+VAL
          NLIMS=NLIMS-2
          IF (NLIMS.NE.0) GO TO 10
          GO TO 999
        ELSEIF(ABS(AA).LT.XMIN.AND.J.EQ.4) THEN
C           Bin is too small -- set VAL = 0. -- FEP
          IBAD=IBAD+1
          NLIMS=NLIMS-2
          IF (NLIMS.NE.0) GO TO 10
          GO TO 999
        ENDIF
25    TVAL=VAL
      IF(NMAX.EQ.2) THEN
        SSDINT=VAL
        GO TO 999
      ENDIF
      IF(NLIMS.GT.(NMAX-2)) THEN
        WRITE(LOUT,50) SSDINT,NMAX,BB-AA,BB+AA
50      FORMAT (' ERROR IN SSDINT, SSDINT,NMAX,XL,XR=',G15.7,I5,2G15.7)
        RETURN
      ENDIF
      XLIMS(NLIMS+1)=BB
      XLIMS(NLIMS+2)=BB+AA
      XLIMS(NLIMS)=BB
      NLIMS=NLIMS+2
      GO TO 10
C
999   IF(IBAD.GT.0) THEN
        WRITE(LOUT,*) 'WARNING IN SSXINT: BAD CONVERGENCE FOR ',IBAD,
     $  ' INTERVALS.'
      ENDIF
      RETURN
      END