GEANT321/ggeom/gvpsqr.F

   1 *
   2 * $Id$
   3 *
   4 * $Log$
   5 * Revision 1.1.1.1  1995/10/24 10:20:57  cernlib
   6 * Geant
   7 *
   8 *
   9 #include "geant321/pilot.h"
  10 *CMZ :  3.21/02 29/03/94  15.41.31  by  S.Giani
  11 *-- Author :
  12 *
  13       SUBROUTINE GVPSQR (CBA, SOL, NSOL)
  14 ************************************************************************
  15 *                                                                      *
  16 *     SUBROUTINE GVPSQR (CBA,SOL,NSOL)             870924  VP          *
  17 *                                                                      *
  18 *       SOLVE  QUADRATIC  EQUATION                                     *
  19 *                                                                      *
  20 *   ARGUMENTS:                                                         *
  21 *       CBA     Array of coeff's A0 + A1*x + A2*x**2                   *
  22 *       SOL     Solutions                                              *
  23 *       NSOL    Number of solutions :                                  *
  24 *               if zero - SOL(1)= extremum                             *
  25 *               if -ve  - No solution at all                           *
  26 *                                                                      *
  27 ************************************************************************
  28
  29       PARAMETER      (ZERO2=1.E-12)
  30       REAL           CBA(3), SOL(2), SWAP
  31 *-----------------------------------------------------------------------
  32
  33       A = CBA(3)
  34       B = CBA(2)*.5
  35       C = CBA(1)
  36       IF (B.LT.0.)              THEN
  37         A = -A
  38         B = -B
  39         C = -C
  40       ENDIF
  41
  42       AMX = MAX (ABS(A),ABS(B),ABS(C))
  43       IF (AMX.LE.0.)            GO TO 100
  44       A   = A/AMX
  45       B   = B/AMX
  46       C   = C/AMX
  47
  48       DIS = B**2 - A*C
  49       NSOL = 1
  50       IF (ABS(DIS) .LE. ZERO2)  DIS = 0.
  51       IF (DIS.LT.0.)            THEN
  52         NSOL = 0
  53         DIS  = 0.
  54       ENDIF
  55
  56       IF (DIS.GT.0.)            DIS = SQRT(DIS)
  57       BDIS = B + DIS
  58       IF (ABS(C).GT.1.E+10*BDIS)        GO TO 100
  59       SOL(1) = 0.
  60       IF (ABS(BDIS).LE.0.)      GO TO 999
  61       SOL(1) = (-C/BDIS)
  62       IF (DIS.LE.0.)            GO TO 999
  63       IF (BDIS.GE.1.E+10*ABS(A))        GO TO 999
  64       NSOL   = 2
  65       SOL(2) = (-BDIS/A)
  66       IF (SOL(1).GT.SOL(2))     THEN
  67         SWAP = SOL(1)
  68         SOL(1) = SOL(2)
  69         SOL(2) = SWAP
  70       ENDIF
  71       GO TO 999
  72
  73 *
  74 **      No solutions
  75   100 NSOL = -1
  76
  77   999 RETURN
  78       END