DEVCHK(3)

SYNOPSIS
SUBROUTINE DEVCHK (LOUT, KPRINT, NPTS, XEV, FEV, DEV, FEV2, FAIL)

NAME
devchk - Test evaluation accuracy of DCHFDV and DCHFEV for DPCHQ1.

LIBRARY
SLATEC (PCHIP)

TYPE
DOUBLE PRECISION (EVCHCK-S, DEVCHK-D)

KEYWORDS
PCHIP EVALUATOR QUICK CHECK

AUTHOR
Fritsch, F. N., (LLNL)

DESCRIPTION
-------- CODE TO TEST EVALUATION ACCURACY OF DCHFDV AND DCHFEV ------- USING FUNCTION AND DERIVATIVE VALUES FROM A CUBIC (COMPUTED IN DOUBLE PRECISION) AT NINT DIFFERENT (X1,X2) PAIRS: 1. CHECKS THAT DCHFDV AND DCHFEV BOTH REPRODUCE ENDPOINT VALUES. 2. EVALUATES AT NPTS POINTS, 10 OF WHICH ARE OUTSIDE THE INTERVAL AND: A. CHECKS ACCURACY OF DCHFDV FUNCTION AND DERIVATIVE VALUES AGAINST EXACT VALUES. B. CHECKS THAT RETURNED VALUES OF NEXT SUM TO 10. C. CHECKS THAT FUNCTION VALUES FROM DCHFEV AGREE WITH THOSE FROM DCHFDV. FORTRAN INTRINSICS USED: ABS, MAX, MIN. FORTRAN LIBRARY ROUTINES USED: SQRT, (READ), (WRITE). SLATEC LIBRARY ROUTINES USED: DCHFDV, DCHFEV, D1MACH, RAND. OTHER ROUTINES USED: DFDTRU.

ROUTINES CALLED
D1MACH, DCHFDV, DCHFEV, DFDTRU, RAND

REVISION HISTORY (YYMMDD)
820601 DATE WRITTEN
820624 CONVERTED TO QUICK CHECK FOR SLATEC LIBRARY.
820630 1. MODIFIED DEFINITIONS OF RELATIVE ERROR AND TEST TOLERANCES. 2. VARIOUS IMPROVEMENTS TO OUTPUT FORMATS.
820716 1. SET MACHEP VIA A CALL TO D1MACH. 2. CHANGED FROM FORTLIB'S RANF TO SLATEC'S RAND.
890628 1. Removed unnecessary IMPLICIT declaration. 2. Removed unnecessary variable NEV. 3. Other changes to reduce S.P./D.P. differences.
890629 Added RERR to DOUBLE PRECISION declaration.
890706 Cosmetic changes to prologue. (WRB)
890831 Modified array declarations. (WRB)
890911 Removed unnecessary intrinsics. (WRB)
891214 Prologue converted to Version 4.0 format. (BAB)
900315 Revised prologue and improved some output formats. (FNF) Also moved formats to end to be consistent with other PCHIP quick checks.
900316 Additional minor cosmetic changes. (FNF)
900321 Changed name of DFTRUE to DFDTRU and made additional minor cosmetic changes. (FNF)
901130 Added 1P's to formats and revised some to reduce maximum line length. (FNF)
910708 Minor modifications in use of KPRINT. (WRB)
910801 Added EXTERNAL statement for RAND due to problem on IBM RS 6000. (WRB)
910819 Changed argument to RAND function from a D.P. zero to a S.P. zero. (WRB)