DOUBLE PRECISION FUNCTION DPCHIA(N,X,F,D,INCFD,SKIP,A,B,IERR)
C***BEGIN PROLOGUE  DPCHIA
C***DATE WRITTEN   820730   (YYMMDD)
C***REVISION DATE  870707   (YYMMDD)
C***CATEGORY NO.  E3,H2A2
C***KEYWORDS  LIBRARY=SLATEC(PCHIP),
C             TYPE=DOUBLE PRECISION(PCHIA-S DPCHIA-D),
C             CUBIC HERMITE INTERPOLATION,NUMERICAL INTEGRATION,
C             QUADRATURE
C***AUTHOR  FRITSCH, F. N., (LLNL)
C             MATHEMATICS AND STATISTICS DIVISION
C             LAWRENCE LIVERMORE NATIONAL LABORATORY
C             P.O. BOX 808  (L-316)
C             LIVERMORE, CA  94550
C             FTS 532-4275, (415) 422-4275
C***PURPOSE  Evaluate the definite integral of a piecewise cubic
C            Hermite function over an arbitrary interval.
C***DESCRIPTION
C
C       **** Double Precision version of PCHIA ****
C
C          DPCHIA:  Piecewise Cubic Hermite Integrator, Arbitrary limits
C
C     Evaluates the definite integral of the cubic Hermite function
C     defined by  N, X, F, D  over the interval [A, B].
C
C     To provide compatibility with DPCHIM and DPCHIC, includes an
C     increment between successive values of the F- and D-arrays.
C
C ----------------------------------------------------------------------
C
C  Calling sequence:
C
C        PARAMETER  (INCFD = ...)
C        INTEGER  N, IERR
C        DOUBLE PRECISION  X(N), F(INCFD,N), D(INCFD,N), A, B
C        DOUBLE PRECISION  VALUE, DPCHIA
C        LOGICAL  SKIP
C
C        VALUE = DPCHIA (N, X, F, D, INCFD, SKIP, A, B, IERR)
C
C   Parameters:
C
C     VALUE -- (output) value of the requested integral.
C
C     N -- (input) number of data points.  (Error return if N.LT.2 .)
C
C     X -- (input) real*8 array of independent variable values.  The
C           elements of X must be strictly increasing:
C                X(I-1) .LT. X(I),  I = 2(1)N.
C           (Error return if not.)
C
C     F -- (input) real*8 array of function values.  F(1+(I-1)*INCFD) is
C           the value corresponding to X(I).
C
C     D -- (input) real*8 array of derivative values.  D(1+(I-1)*INCFD)
C           is the value corresponding to X(I).
C
C     INCFD -- (input) increment between successive values in F and D.
C           (Error return if  INCFD.LT.1 .)
C
C     SKIP -- (input/output) logical variable which should be set to
C           .TRUE. if the user wishes to skip checks for validity of
C           preceding parameters, or to .FALSE. otherwise.
C           This will save time in case these checks have already
C           been performed (say, in DPCHIM or DPCHIC).
C           SKIP will be set to .TRUE. on return with IERR.GE.0 .
C
C     A,B -- (input) the limits of integration.
C           NOTE:  There is no requirement that [A,B] be contained in
C                  [X(1),X(N)].  However, the resulting integral value
C                  will be highly suspect, if not.
C
C     IERR -- (output) error flag.
C           Normal return:
C              IERR = 0  (no errors).
C           Warning errors:
C              IERR = 1  if  A  is outside the interval [X(1),X(N)].
C              IERR = 2  if  B  is outside the interval [X(1),X(N)].
C              IERR = 3  if both of the above are true.  (Note that this
C                        means that either [A,B] contains data interval
C                        or the intervals do not intersect at all.)
C           "Recoverable" errors:
C              IERR = -1  if N.LT.2 .
C              IERR = -2  if INCFD.LT.1 .
C              IERR = -3  if the X-array is not strictly increasing.
C                (Value has not been computed in any of these cases.)
C               NOTE:  The above errors are checked in the order listed,
C                   and following arguments have **NOT** been validated.
C
C***REFERENCES  (NONE)
C***ROUTINES CALLED  DCHFIV,DPCHID,XERROR
C***END PROLOGUE  DPCHIA