C DSPS 10
C ..................................................................DSPS 20
C DSPS 30
C SUBROUTINE DCSPS DSPS 40
C DSPS 50
C PURPOSE DSPS 60
C COMPUTES THE VALUE OF AN N-TERM EXPANSION IN SHIFTED DSPS 70
C CHEBYSHEV POLYNOMIALS WITH COEFFICIENT VECTOR C DSPS 80
C FOR ARGUMENT VALUE X. DSPS 90
C DSPS 100
C USAGE DSPS 110
C CALL DCSPS(Y,X,C,N) DSPS 120
C DSPS 130
C DESCRIPTION OF PARAMETERS DSPS 140
C Y - RESULT VALUE DSPS 150
C DOUBLE PRECISION VARIABLE DSPS 160
C X - ARGUMENT VALUE DSPS 170
C DOUBLE PRECISION VARIABLE DSPS 180
C C - COEFFICIENT VECTOR OF GIVEN EXPANSION DSPS 190
C COEFFICIENTS ARE ORDERED FROM LOW TO HIGH DSPS 200
C DOUBLE PRECISION VECTOR DSPS 210
C N - DIMENSION OF COEFFICIENT VECTOR C DSPS 220
C DSPS 230
C REMARKS DSPS 240
C OPERATION IS BYPASSED IN CASE N LESS THAN 1 DSPS 250
C DSPS 260
C SUBROUTINES AND FUNCTION SUBPROGRAMS REQUIRED DSPS 270
C NONE DSPS 280
C DSPS 290
C METHOD DSPS 300
C DEFINITION DSPS 310
C Y=SUM(C(I)*TS(I-1,X), SUMMED OVER I FROM 1 TO N). DSPS 320
C EVALUATION IS DONE BY MEANS OF BACKWARD RECURSION DSPS 330
C USING THE RECURRENCE EQUATION FOR SHIFTED DSPS 340
C CHEBYSHEV POLYNOMIALS DSPS 350
C TS(N+1,X)=(4*X-2)*TS(N,X)-TS(N-1,X). DSPS 360
C DSPS 370
C ..................................................................DSPS 380
C DSPS 390
SUBROUTINE DCSPS(Y,X,C,N) DSPS 400
C DSPS 410
DIMENSION C(1) DSPS 420
DOUBLE PRECISION C,Y,X,H0,H1,H2,ARG DSPS 430
C DSPS 440
C TEST OF DIMENSION DSPS 450
IF(N)1,1,2 DSPS 460
1 RETURN DSPS 470
C DSPS 480
2 IF(N-2)3,4,4 DSPS 490
3 Y=C(1) DSPS 500
RETURN DSPS 510
C DSPS 520
C INITIALIZATION DSPS 530
4 ARG=X+X-1.D0 DSPS 540
ARG=ARG+ARG DSPS 550
H1=0.D0 DSPS 560
H0=0.D0 DSPS 570
DO 5 I=1,N DSPS 580
K=N-I DSPS 590
H2=H1 DSPS 600
H1=H0 DSPS 610
5 H0=ARG*H1-H2+C(K+1) DSPS 620
Y=0.5D0*(C(1)-H2+H0) DSPS 630
RETURN DSPS 640
END DSPS 650