C DTFE 10
C ..................................................................DTFE 20
C DTFE 30
C SUBROUTINE DQTFE DTFE 40
C DTFE 50
C PURPOSE DTFE 60
C TO COMPUTE THE VECTOR OF INTEGRAL VALUES FOR A GIVEN DTFE 70
C EQUIDISTANT TABLE OF FUNCTION VALUES. DTFE 80
C DTFE 90
C USAGE DTFE 100
C CALL DQTFE (H,Y,Z,NDIM) DTFE 110
C DTFE 120
C DESCRIPTION OF PARAMETERS DTFE 130
C H - DOUBLE PRECISION INCREMENT OF ARGUMENT VALUES. DTFE 140
C Y - DOUBLE PRECISION INPUT VECTOR OF FUNCTION VALUES. DTFE 150
C Z - RESULTING DOUBLE PRECISION VECTOR OF INTEGRAL DTFE 160
C VALUES. Z MAY BE IDENTICAL WITH Y. DTFE 170
C NDIM - THE DIMENSION OF VECTORS Y AND Z. DTFE 180
C DTFE 190
C REMARKS DTFE 200
C NO ACTION IN CASE NDIM LESS THAN 1. DTFE 210
C DTFE 220
C SUBROUTINES AND FUNCTION SUBPROGRAMS REQUIRED DTFE 230
C NONE DTFE 240
C DTFE 250
C METHOD DTFE 260
C BEGINNING WITH Z(1)=0, EVALUATION OF VECTOR Z IS DONE BY DTFE 270
C MEANS OF TRAPEZOIDAL RULE (SECOND ORDER FORMULA). DTFE 280
C FOR REFERENCE, SEE DTFE 290
C F.B.HILDEBRAND, INTRODUCTION TO NUMERICAL ANALYSIS, DTFE 300
C MCGRAW-HILL, NEW YORK/TORONTO/LONDON, 1956, PP.75. DTFE 310
C DTFE 320
C ..................................................................DTFE 330
C DTFE 340
SUBROUTINE DQTFE(H,Y,Z,NDIM) DTFE 350
C DTFE 360
C DTFE 370
DIMENSION Y(1),Z(1) DTFE 380
DOUBLE PRECISION Y,Z,H,HH,SUM1,SUM2 DTFE 390
C DTFE 400
SUM2=0.D0 DTFE 410
IF(NDIM-1)4,3,1 DTFE 420
1 HH=.5D0*H DTFE 430
C DTFE 440
C INTEGRATION LOOP DTFE 450
DO 2 I=2,NDIM DTFE 460
SUM1=SUM2 DTFE 470
SUM2=SUM2+HH*(Y(I)+Y(I-1)) DTFE 480
2 Z(I-1)=SUM1 DTFE 490
3 Z(NDIM)=SUM2 DTFE 500
4 RETURN DTFE 510
END DTFE 520