*DECK ZKSCL SUBROUTINE ZKSCL (ZRR, ZRI, FNU, N, YR, YI, NZ, RZR, RZI, ASCLE, + TOL, ELIM) C***BEGIN PROLOGUE ZKSCL C***SUBSIDIARY C***PURPOSE Subsidiary to ZBESK C***LIBRARY SLATEC C***TYPE ALL (CKSCL-A, ZKSCL-A) C***AUTHOR Amos, D. E., (SNL) C***DESCRIPTION C C SET K FUNCTIONS TO ZERO ON UNDERFLOW, CONTINUE RECURRENCE C ON SCALED FUNCTIONS UNTIL TWO MEMBERS COME ON SCALE, THEN C RETURN WITH MIN(NZ+2,N) VALUES SCALED BY 1/TOL. C C***SEE ALSO ZBESK C***ROUTINES CALLED ZABS, ZLOG, ZUCHK C***REVISION HISTORY (YYMMDD) C 830501 DATE WRITTEN C 910415 Prologue converted to Version 4.0 format. (BAB) C 930122 Added ZLOG to EXTERNAL statement. (RWC) C***END PROLOGUE ZKSCL C COMPLEX CK,CS,CY,CZERO,RZ,S1,S2,Y,ZR,ZD,CELM DOUBLE PRECISION ACS, AS, ASCLE, CKI, CKR, CSI, CSR, CYI, * CYR, ELIM, FN, FNU, RZI, RZR, STR, S1I, S1R, S2I, * S2R, TOL, YI, YR, ZEROI, ZEROR, ZRI, ZRR, ZABS, * ZDR, ZDI, CELMR, ELM, HELIM, ALAS INTEGER I, IC, IDUM, KK, N, NN, NW, NZ DIMENSION YR(N), YI(N), CYR(2), CYI(2) EXTERNAL ZABS, ZLOG DATA ZEROR,ZEROI / 0.0D0 , 0.0D0 / C***FIRST EXECUTABLE STATEMENT ZKSCL NZ = 0 IC = 0 NN = MIN(2,N) DO 10 I=1,NN S1R = YR(I) S1I = YI(I) CYR(I) = S1R CYI(I) = S1I AS = ZABS(S1R,S1I) ACS = -ZRR + LOG(AS) NZ = NZ + 1 YR(I) = ZEROR YI(I) = ZEROI IF (ACS.LT.(-ELIM)) GO TO 10 CALL ZLOG(S1R, S1I, CSR, CSI, IDUM) CSR = CSR - ZRR CSI = CSI - ZRI STR = EXP(CSR)/TOL CSR = STR*COS(CSI) CSI = STR*SIN(CSI) CALL ZUCHK(CSR, CSI, NW, ASCLE, TOL) IF (NW.NE.0) GO TO 10 YR(I) = CSR YI(I) = CSI IC = I NZ = NZ - 1 10 CONTINUE IF (N.EQ.1) RETURN IF (IC.GT.1) GO TO 20 YR(1) = ZEROR YI(1) = ZEROI NZ = 2 20 CONTINUE IF (N.EQ.2) RETURN IF (NZ.EQ.0) RETURN FN = FNU + 1.0D0 CKR = FN*RZR CKI = FN*RZI S1R = CYR(1) S1I = CYI(1) S2R = CYR(2) S2I = CYI(2) HELIM = 0.5D0*ELIM ELM = EXP(-ELIM) CELMR = ELM ZDR = ZRR ZDI = ZRI C C FIND TWO CONSECUTIVE Y VALUES ON SCALE. SCALE RECURRENCE IF C S2 GETS LARGER THAN EXP(ELIM/2) C DO 30 I=3,N KK = I CSR = S2R CSI = S2I S2R = CKR*CSR - CKI*CSI + S1R S2I = CKI*CSR + CKR*CSI + S1I S1R = CSR S1I = CSI CKR = CKR + RZR CKI = CKI + RZI AS = ZABS(S2R,S2I) ALAS = LOG(AS) ACS = -ZDR + ALAS NZ = NZ + 1 YR(I) = ZEROR YI(I) = ZEROI IF (ACS.LT.(-ELIM)) GO TO 25 CALL ZLOG(S2R, S2I, CSR, CSI, IDUM) CSR = CSR - ZDR CSI = CSI - ZDI STR = EXP(CSR)/TOL CSR = STR*COS(CSI) CSI = STR*SIN(CSI) CALL ZUCHK(CSR, CSI, NW, ASCLE, TOL) IF (NW.NE.0) GO TO 25 YR(I) = CSR YI(I) = CSI NZ = NZ - 1 IF (IC.EQ.KK-1) GO TO 40 IC = KK GO TO 30 25 CONTINUE IF(ALAS.LT.HELIM) GO TO 30 ZDR = ZDR - ELIM S1R = S1R*CELMR S1I = S1I*CELMR S2R = S2R*CELMR S2I = S2I*CELMR 30 CONTINUE NZ = N IF(IC.EQ.N) NZ=N-1 GO TO 45 40 CONTINUE NZ = KK - 2 45 CONTINUE DO 50 I=1,NZ YR(I) = ZEROR YI(I) = ZEROI 50 CONTINUE RETURN END