SLATEC Routines --- QAWCE ---

```*DECK QAWCE
SUBROUTINE QAWCE (F, A, B, C, EPSABS, EPSREL, LIMIT, RESULT,
+   ABSERR, NEVAL, IER, ALIST, BLIST, RLIST, ELIST, IORD, LAST)
C***BEGIN PROLOGUE  QAWCE
C***PURPOSE  The routine calculates an approximation result to a
C            CAUCHY PRINCIPAL VALUE I = Integral of F*W over (A,B)
C            (W(X) = 1/(X-C), (C.NE.A, C.NE.B), hopefully satisfying
C            following claim for accuracy
C            ABS(I-RESULT).LE.MAX(EPSABS,EPSREL*ABS(I))
C***CATEGORY  H2A2A1, J4
C***TYPE      SINGLE PRECISION (QAWCE-S, DQAWCE-D)
C***KEYWORDS  AUTOMATIC INTEGRATOR, CAUCHY PRINCIPAL VALUE,
C             SPECIAL-PURPOSE
C***AUTHOR  Piessens, Robert
C             Applied Mathematics and Programming Division
C             K. U. Leuven
C           de Doncker, Elise
C             Applied Mathematics and Programming Division
C             K. U. Leuven
C***DESCRIPTION
C
C        Computation of a CAUCHY PRINCIPAL VALUE
C        Standard fortran subroutine
C        Real version
C
C        PARAMETERS
C         ON ENTRY
C            F      - Real
C                     Function subprogram defining the integrand
C                     function F(X). The actual name for F needs to be
C                     declared E X T E R N A L in the driver program.
C
C            A      - Real
C                     Lower limit of integration
C
C            B      - Real
C                     Upper limit of integration
C
C            C      - Real
C                     Parameter in the WEIGHT function, C.NE.A, C.NE.B
C                     If C = A OR C = B, the routine will end with
C                     IER = 6.
C
C            EPSABS - Real
C                     Absolute accuracy requested
C            EPSREL - Real
C                     Relative accuracy requested
C                     If  EPSABS.LE.0
C                     and EPSREL.LT.MAX(50*REL.MACH.ACC.,0.5D-28),
C                     the routine will end with IER = 6.
C
C            LIMIT  - Integer
C                     Gives an upper bound on the number of subintervals
C                     in the partition of (A,B), LIMIT.GE.1
C
C         ON RETURN
C            RESULT - Real
C                     Approximation to the integral
C
C            ABSERR - Real
C                     Estimate of the modulus of the absolute error,
C                     which should equal or exceed ABS(I-RESULT)
C
C            NEVAL  - Integer
C                     Number of integrand evaluations
C
C            IER    - Integer
C                     IER = 0 Normal and reliable termination of the
C                             routine. It is assumed that the requested
C                             accuracy has been achieved.
C                     IER.GT.0 Abnormal termination of the routine
C                             the estimates for integral and error are
C                             less reliable. It is assumed that the
C                             requested accuracy has not been achieved.
C            ERROR MESSAGES
C                     IER = 1 Maximum number of subdivisions allowed
C                             has been achieved. One can allow more sub-
C                             divisions by increasing the value of
C                             LIMIT. However, if this yields no
C                             improvement it is advised to analyze the
C                             the integrand, in order to determine the
C                             the integration difficulties. If the
C                             position of a local difficulty can be
C                             determined (e.g. SINGULARITY,
C                             DISCONTINUITY within the interval) one
C                             will probably gain from splitting up the
C                             interval at this point and calling
C                             appropriate integrators on the subranges.
C                         = 2 The occurrence of roundoff error is detec-
C                             ted, which prevents the requested
C                             tolerance from being achieved.
C                         = 3 Extremely bad integrand behaviour
C                             occurs at some interior points of
C                             the integration interval.
C                         = 6 The input is invalid, because
C                             C = A or C = B or
C                             (EPSABS.LE.0 and
C                              EPSREL.LT.MAX(50*REL.MACH.ACC.,0.5D-28))
C                             or LIMIT.LT.1.
C                             RESULT, ABSERR, NEVAL, RLIST(1), ELIST(1),
C                             IORD(1) and LAST are set to zero. ALIST(1)
C                             and BLIST(1) are set to A and B
C                             respectively.
C
C            ALIST   - Real
C                      Vector of dimension at least LIMIT, the first
C                       LAST  elements of which are the left
C                      end points of the subintervals in the partition
C                      of the given integration range (A,B)
C
C            BLIST   - Real
C                      Vector of dimension at least LIMIT, the first
C                       LAST  elements of which are the right
C                      end points of the subintervals in the partition
C                      of the given integration range (A,B)
C
C            RLIST   - Real
C                      Vector of dimension at least LIMIT, the first
C                       LAST  elements of which are the integral
C                      approximations on the subintervals
C
C            ELIST   - Real
C                      Vector of dimension LIMIT, the first  LAST
C                      elements of which are the moduli of the absolute
C                      error estimates on the subintervals
C
C            IORD    - Integer
C                      Vector of dimension at least LIMIT, the first K
C                      elements of which are pointers to the error
C                      estimates over the subintervals, so that
C                      ELIST(IORD(1)), ..., ELIST(IORD(K)) with K = LAST
C                      If LAST.LE.(LIMIT/2+2), and K = LIMIT+1-LAST
C                      otherwise, form a decreasing sequence
C
C            LAST    - Integer
C                      Number of subintervals actually produced in
C                      the subdivision process
C
C***REFERENCES  (NONE)
C***ROUTINES CALLED  QC25C, QPSRT, R1MACH
C***REVISION HISTORY  (YYMMDD)
C   800101  DATE WRITTEN
C   890531  Changed all specific intrinsics to generic.  (WRB)
C   890831  Modified array declarations.  (WRB)
C   890831  REVISION DATE from Version 3.2
C   891214  Prologue converted to Version 4.0 format.  (BAB)
C***END PROLOGUE  QAWCE
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