C QG8 10
C ..................................................................QG8 20
C QG8 30
C SUBROUTINE QG8 QG8 40
C QG8 50
C PURPOSE QG8 60
C TO COMPUTE INTEGRAL(FCT(X), SUMMED OVER X FROM XL TO XU) QG8 70
C QG8 80
C USAGE QG8 90
C CALL QG8 (XL,XU,FCT,Y) QG8 100
C PARAMETER FCT REQUIRES AN EXTERNAL STATEMENT QG8 110
C QG8 120
C DESCRIPTION OF PARAMETERS QG8 130
C XL - THE LOWER BOUND OF THE INTERVAL. QG8 140
C XU - THE UPPER BOUND OF THE INTERVAL. QG8 150
C FCT - THE NAME OF AN EXTERNAL FUNCTION SUBPROGRAM USED. QG8 160
C Y - THE RESULTING INTEGRAL VALUE. QG8 170
C QG8 180
C REMARKS QG8 190
C NONE QG8 200
C QG8 210
C SUBROUTINES AND FUNCTION SUBPROGRAMS REQUIRED QG8 220
C THE EXTERNAL FUNCTION SUBPROGRAM FCT(X) MUST BE FURNISHED QG8 230
C BY THE USER. QG8 240
C QG8 250
C METHOD QG8 260
C EVALUATION IS DONE BY MEANS OF 8-POINT GAUSS QUADRATURE QG8 270
C FORMULA, WHICH INTEGRATES POLYNOMIALS UP TO DEGREE 15 QG8 280
C EXACTLY. QG8 290
C FOR REFERENCE, SEE QG8 300
C V.I.KRYLOV, APPROXIMATE CALCULATION OF INTEGRALS, QG8 310
C MACMILLAN, NEW YORK/LONDON, 1962, PP.100-111 AND 337-338. QG8 320
C QG8 330
C ..................................................................QG8 340
C QG8 350
SUBROUTINE QG8(XL,XU,FCT,Y) QG8 360
C QG8 370
C QG8 380
A=.5*(XU+XL) QG8 390
B=XU-XL QG8 400
C=.4801449*B QG8 410
Y=.05061427*(FCT(A+C)+FCT(A-C)) QG8 420
C=.3983332*B QG8 430
Y=Y+.1111905*(FCT(A+C)+FCT(A-C)) QG8 440
C=.2627662*B QG8 450
Y=Y+.1568533*(FCT(A+C)+FCT(A-C)) QG8 460
C=.09171732*B QG8 470
Y=B*(Y+.1813419*(FCT(A+C)+FCT(A-C))) QG8 480
RETURN QG8 490
END QG8 500