The routine and its subsidiaries will now return an error status as supplied by
SUBROUTINE PDA_DBSQAD (T, BCOEF, N, K, X1, X2, BQUAD, WORK, STATUS)
***BEGIN PROLOGUE PDA_DBSQAD
***PURPOSE Compute the integral of a K-th order B-spline using the
***CATEGORY H2A2A1, E3, K6
***TYPE DOUBLE PRECISION (BSQAD-S, PDA_DBSQAD-D)
***KEYWORDS INTEGRAL OF B-SPLINES, QUADRATURE
***AUTHOR Amos, D. E., (SNLA)
Abstract **** a double precision routine ****
PDA_DBSQAD computes the integral on (X1,X2) of a K-th order
B-spline using the B-representation (T,BCOEF,N,K). Orders
K as high as 20 are permitted by applying a 2, 6, or 10
point Gauss formula on subintervals of (X1,X2) which are
formed by included (distinct) knots.
If orders K greater than 20 are needed, use DBFQAD with
F(X) = 1.
The maximum number of significant digits obtainable in
PDA_DBSQAD is the smaller of 18 and the number of digits
carried in double precision arithmetic.
Description of Arguments
Input T,BCOEF,X1,X2 are double precision
T - knot array of length N+K
BCOEF - B-spline coefficient array of length N
N - length of coefficient array
K - order of B-spline, 1 .LE. K .LE. 20
X1,X2 - end points of quadrature interval in
T(K) .LE. X .LE. T(N+1)
Output BQUAD,WORK are double precision
BQUAD - integral of the B-spline over (X1,X2)
WORK - work vector of length 3*K
STATUS - Returned error status.
The status must be zero on entry. This
routine does not check the status on entry.
Improper input is a fatal error
***REFERENCES D. E. Amos, Quadrature subroutines for splines and
B-splines, Report SAND79-1825, Sandia Laboratories,
***ROUTINES CALLED PDA_DBVALU, PDA_DINTRV, PDA_XERMSG
***REVISION HISTORY (YYMMDD)
800901 DATE WRITTEN
890531 Changed all specific intrinsics to generic. (WRB)
890531 REVISION DATE from Version 3.2
891214 Prologue converted to Version 4.0 format. (BAB)
900315 CALLs to XERROR changed to CALLs to PDA_XERMSG. (THJ)
900326 Removed duplicate information from DESCRIPTION section.
920501 Reformatted the REFERENCES section. (WRB)
950403 Implement status. (HME)
***END PROLOGUE PDA_DBSQAD