SLATEC Routines --- RJ ---


*DECK RJ
      REAL FUNCTION RJ (X, Y, Z, P, IER)
C***BEGIN PROLOGUE  RJ
C***PURPOSE  Compute the incomplete or complete (X or Y or Z is zero)
C            elliptic integral of the 3rd kind.  For X, Y, and Z non-
C            negative, at most one of them zero, and P positive,
C             RJ(X,Y,Z,P) = Integral from zero to infinity of
C                                  -1/2     -1/2     -1/2     -1
C                        (3/2)(t+X)    (t+Y)    (t+Z)    (t+P)  dt.
C***LIBRARY   SLATEC
C***CATEGORY  C14
C***TYPE      SINGLE PRECISION (RJ-S, DRJ-D)
C***KEYWORDS  COMPLETE ELLIPTIC INTEGRAL, DUPLICATION THEOREM,
C             INCOMPLETE ELLIPTIC INTEGRAL, INTEGRAL OF THE THIRD KIND,
C             TAYLOR SERIES
C***AUTHOR  Carlson, B. C.
C             Ames Laboratory-DOE
C             Iowa State University
C             Ames, IA  50011
C           Notis, E. M.
C             Ames Laboratory-DOE
C             Iowa State University
C             Ames, IA  50011
C           Pexton, R. L.
C             Lawrence Livermore National Laboratory
C             Livermore, CA  94550
C***DESCRIPTION
C
C   1.     RJ
C          Standard FORTRAN function routine
C          Single precision version
C          The routine calculates an approximation result to
C          RJ(X,Y,Z,P) = Integral from zero to infinity of
C
C                                -1/2     -1/2     -1/2     -1
C                      (3/2)(t+X)    (t+Y)    (t+Z)    (t+P)  dt,
C
C          where X, Y, and Z are nonnegative, at most one of them is
C          zero, and P is positive.  If X or Y or Z is zero, the
C          integral is COMPLETE.  The duplication theorem is iterated
C          until the variables are nearly equal, and the function is
C          then expanded in Taylor series to fifth order.
C
C
C   2.     Calling Sequence
C          RJ( X, Y, Z, P, IER )
C
C          Parameters On Entry
C          Values assigned by the calling routine
C
C          X      - Single precision, nonnegative variable
C
C          Y      - Single precision, nonnegative variable
C
C          Z      - Single precision, nonnegative variable
C
C          P      - Single precision, positive variable
C
C
C          On  Return     (values assigned by the RJ routine)
C
C          RJ     - Single precision approximation to the integral
C
C          IER    - Integer
C
C                   IER = 0 Normal and reliable termination of the
C                           routine.  It is assumed that the requested
C                           accuracy has been achieved.
C
C                   IER >  0 Abnormal termination of the routine
C
C
C          X, Y, Z, P are unaltered.
C
C
C   3.    Error Messages
C
C         Value of IER assigned by the RJ routine
C
C                  Value Assigned        Error Message Printed
C                  IER = 1               MIN(X,Y,Z) .LT. 0.0E0
C                      = 2               MIN(X+Y,X+Z,Y+Z,P) .LT. LOLIM
C                      = 3               MAX(X,Y,Z,P) .GT. UPLIM
C
C
C
C   4.     Control Parameters
C
C                  Values of LOLIM, UPLIM, and ERRTOL are set by the
C                  routine.
C
C
C          LOLIM and UPLIM determine the valid range of X Y, Z, and P
C
C          LOLIM is not less than the cube root of the value
C          of LOLIM used in the routine for RC.
C
C          UPLIM is not greater than 0.3 times the cube root of
C          the value of UPLIM used in the routine for RC.
C
C
C                     Acceptable Values For:   LOLIM      UPLIM
C                     IBM 360/370 SERIES   :   2.0E-26     3.0E+24
C                     CDC 6000/7000 SERIES :   5.0E-98     3.0E+106
C                     UNIVAC 1100 SERIES   :   5.0E-13     6.0E+11
C                     CRAY                 :   1.32E-822   1.4E+821
C                     VAX 11 SERIES        :   2.5E-13     9.0E+11
C
C
C
C          ERRTOL determines the accuracy of the answer
C
C                 The value assigned by the routine will result
C                 in solution precision within 1-2 decimals of
C                 "machine precision".
C
C
C
C
C          Relative error due to truncation of the series for RJ
C          is less than 3 * ERRTOL ** 6 / (1 - ERRTOL) ** 3/2.
C
C
C
C              The accuracy of the computed approximation to the inte-
C              gral can be controlled by choosing the value of ERRTOL.
C              Truncation of a Taylor series after terms of fifth order
C              Introduces an error less than the amount shown in the
C              second column of the following table for each value of
C              ERRTOL in the first column.  In addition to the trunca-
C              tion error there will be round-off error, but in prac-
C              tice the total error from both sources is usually less
C              than the amount given in the table.
C
C
C
C          Sample choices:  ERRTOL   Relative Truncation
C                                    error less than
C                           1.0E-3    4.0E-18
C                           3.0E-3    3.0E-15
C                           1.0E-2    4.0E-12
C                           3.0E-2    3.0E-9
C                           1.0E-1    4.0E-6
C
C                    Decreasing ERRTOL by a factor of 10 yields six more
C                    decimal digits of accuracy at the expense of one or
C                    two more iterations of the duplication theorem.
C
C *Long Description:
C
C   RJ Special Comments
C
C
C          Check by addition theorem: RJ(X,X+Z,X+W,X+P)
C          + RJ(Y,Y+Z,Y+W,Y+P) + (A-B) * RJ(A,B,B,A) + 3 / SQRT(A)
C          = RJ(0,Z,W,P), where X,Y,Z,W,P are positive and X * Y
C          = Z * W,  A = P * P * (X+Y+Z+W),  B = P * (P+X) * (P+Y),
C          and B - A = P * (P-Z) * (P-W).  The sum of the third and
C          fourth terms on the left side is 3 * RC(A,B).
C
C
C          On Input:
C
C          X, Y, Z, and P are the variables in the integral RJ(X,Y,Z,P).
C
C
C          On Output:
C
C
C          X, Y, Z, and P are unaltered.
C
C          ********************************************************
C
C          Warning: Changes in the program may improve speed at the
C                   expense of robustness.
C
C ------------------------------------------------------------
C
C
C   Special Functions via RJ and RF
C
C
C                  Legendre form of ELLIPTIC INTEGRAL of 3rd kind
C                  ----------------------------------------------
C
C
C                               PHI         2         -1
C                  P(PHI,K,N) = INT (1+N SIN (THETA) )   *
C                                0
C
C                                      2    2         -1/2
C                                 *(1-K  SIN (THETA) )     D THETA
C
C
C                                         2          2   2
C                       = SIN (PHI) RF(COS (PHI), 1-K SIN (PHI),1)
C
C                                  3            2         2   2
C                        -(N/3) SIN (PHI) RJ(COS (PHI),1-K SIN (PHI),
C
C                                 2
C                        1,1+N SIN (PHI))
C
C
C
C                  Bulirsch form of ELLIPTIC INTEGRAL of 3rd kind
C                  ----------------------------------------------
C
C
C                                           2 2    2
C                  EL3(X,KC,P) = X RF(1,1+KC X ,1+X ) +
C
C                                            3          2 2    2     2
C                               +(1/3)(1-P) X  RJ(1,1+KC X ,1+X ,1+PX )
C
C
C                                           2
C                  CEL(KC,P,A,B) = A RF(0,KC ,1) +
C
C                                                     2
C                                 +(1/3)(B-PA) RJ(0,KC ,1,P)
C
C
C
C
C                  Heuman's LAMBDA function
C                  ------------------------
C
C
C                                 2                     2      2    1/2
C                  L(A,B,P) = (COS(A)SIN(B)COS(B)/(1-COS (A)SIN (B))   )
C
C                                           2         2       2
C                            *(SIN(P) RF(COS (P),1-SIN (A) SIN (P),1)
C
C                                 2       3            2       2
C                            +(SIN (A) SIN (P)/(3(1-COS (A) SIN (B))))
C
C                                   2         2       2
C                            *RJ(COS (P),1-SIN (A) SIN (P),1,1-
C
C                                2       2          2       2
C                            -SIN (A) SIN (P)/(1-COS (A) SIN (B))))
C
C
C
C
C                  (PI/2) LAMBDA0(A,B) =L(A,B,PI/2) =
C
C
C                    2                         2       2    -1/2
C               = COS (A)  SIN(B) COS(B) (1-COS (A) SIN (B))
C
C                           2                  2       2
C                  *RF(0,COS (A),1) + (1/3) SIN (A) COS (A)
C
C                                       2       2    -3/2
C                  *SIN(B) COS(B) (1-COS (A) SIN (B))
C
C                           2         2       2          2       2
C                  *RJ(0,COS (A),1,COS (A) COS (B)/(1-COS (A) SIN (B)))
C
C
C
C                  Jacobi ZETA function
C                  --------------------
C
C
C                             2                     2   2    1/2
C                  Z(B,K) = (K/3) SIN(B) COS(B) (1-K SIN (B))
C
C
C                                      2      2   2                2
C                             *RJ(0,1-K ,1,1-K SIN (B)) / RF (0,1-K ,1)
C
C
C    -------------------------------------------------------------------
C
C***REFERENCES  B. C. Carlson and E. M. Notis, Algorithms for incomplete
C                 elliptic integrals, ACM Transactions on Mathematical
C                 Software 7, 3 (September 1981), pp. 398-403.
C               B. C. Carlson, Computing elliptic integrals by
C                 duplication, Numerische Mathematik 33, (1979),
C                 pp. 1-16.
C               B. C. Carlson, Elliptic integrals of the first kind,
C                 SIAM Journal of Mathematical Analysis 8, (1977),
C                 pp. 231-242.
C***ROUTINES CALLED  R1MACH, RC, XERMSG
C***REVISION HISTORY  (YYMMDD)
C   790801  DATE WRITTEN
C   890531  Changed all specific intrinsics to generic.  (WRB)
C   891009  Removed unreferenced statement labels.  (WRB)
C   891009  REVISION DATE from Version 3.2
C   891214  Prologue converted to Version 4.0 format.  (BAB)
C   900315  CALLs to XERROR changed to CALLs to XERMSG.  (THJ)
C   900326  Removed duplicate information from DESCRIPTION section.
C           (WRB)
C   900510  Changed calls to XERMSG to standard form, and some
C           editorial changes.  (RWC)).
C   920501  Reformatted the REFERENCES section.  (WRB)
C***END PROLOGUE  RJ