HIJING/hijing1_36/gauss4.F

   1 * $Id$
   2 C
   3 C
   4 C
   5 C
   6         FUNCTION GAUSS4(F,A,B,EPS)
   7         EXTERNAL F
   8         DIMENSION W(12),X(12)
   9         DATA CONST/1.0E-12/
  10         DATA W/0.1012285,.2223810,.3137067,.3623838,.0271525,
  11      &         .0622535,0.0951585,.1246290,.1495960,.1691565,
  12      &         .1826034,.1894506/
  13         DATA X/0.9602899,.7966665,.5255324,.1834346,.9894009,
  14      &         .9445750,0.8656312,.7554044,.6178762,.4580168,
  15      &         .2816036,.0950125/
  16         SAVE
  17         DELTA=CONST*ABS(A-B)
  18         GAUSS4=0.0
  19         AA=A
  20 5       Y=B-AA
  21         IF(ABS(Y).LE.DELTA) RETURN
  22 2       BB=AA+Y
  23         C1=0.5*(AA+BB)
  24         C2=C1-AA
  25         S8=0.0
  26         S16=0.0
  27         DO 1 I=1,4
  28         U=X(I)*C2
  29 1       S8=S8+W(I)*(F(C1+U)+F(C1-U))
  30         DO 3 I=5,12
  31         U=X(I)*C2
  32 3       S16=S16+W(I)*(F(C1+U)+F(C1-U))
  33         S8=S8*C2
  34         S16=S16*C2
  35         IF(ABS(S16-S8).GT.EPS*(1.+ABS(S16))) GOTO 4
  36         GAUSS4=GAUSS4+S16
  37         AA=BB
  38         GOTO 5
  39 4       Y=0.5*Y
  40         IF(ABS(Y).GT.DELTA) GOTO 2
  41         WRITE(6,7)
  42         GAUSS4=0.0
  43         RETURN
  44 7       FORMAT(1X,'GAUSS4....TOO HIGH ACURACY REQUIRED')
  45         END