Mercurial > octave-nkf
view libcruft/amos/cwrsk.f @ 14164:a737b3fb9c4d stable ss-3-5-92
snapshot 3.5.92
* configure.ac (AC_INIT): Version is now 3.5.92.
(OCTAVE_RELEASE_DATE): Now 2012-01-06.
author | John W. Eaton <jwe@octave.org> |
---|---|
date | Fri, 06 Jan 2012 14:34:06 -0500 |
parents | 82be108cc558 |
children |
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SUBROUTINE CWRSK(ZR, FNU, KODE, N, Y, NZ, CW, TOL, ELIM, ALIM) C***BEGIN PROLOGUE CWRSK C***REFER TO CBESI,CBESK C C CWRSK COMPUTES THE I BESSEL FUNCTION FOR RE(Z).GE.0.0 BY C NORMALIZING THE I FUNCTION RATIOS FROM CRATI BY THE WRONSKIAN C C***ROUTINES CALLED CBKNU,CRATI,R1MACH C***END PROLOGUE CWRSK COMPLEX CINU, CSCL, CT, CW, C1, C2, RCT, ST, Y, ZR REAL ACT, ACW, ALIM, ASCLE, ELIM, FNU, S1, S2, TOL, YY INTEGER I, KODE, N, NW, NZ DIMENSION Y(N), CW(2) C----------------------------------------------------------------------- C I(FNU+I-1,Z) BY BACKWARD RECURRENCE FOR RATIOS C Y(I)=I(FNU+I,Z)/I(FNU+I-1,Z) FROM CRATI NORMALIZED BY THE C WRONSKIAN WITH K(FNU,Z) AND K(FNU+1,Z) FROM CBKNU. C----------------------------------------------------------------------- NZ = 0 CALL CBKNU(ZR, FNU, KODE, 2, CW, NW, TOL, ELIM, ALIM) IF (NW.NE.0) GO TO 50 CALL CRATI(ZR, FNU, N, Y, TOL) C----------------------------------------------------------------------- C RECUR FORWARD ON I(FNU+1,Z) = R(FNU,Z)*I(FNU,Z), C R(FNU+J-1,Z)=Y(J), J=1,...,N C----------------------------------------------------------------------- CINU = CMPLX(1.0E0,0.0E0) IF (KODE.EQ.1) GO TO 10 YY = AIMAG(ZR) S1 = COS(YY) S2 = SIN(YY) CINU = CMPLX(S1,S2) 10 CONTINUE C----------------------------------------------------------------------- C ON LOW EXPONENT MACHINES THE K FUNCTIONS CAN BE CLOSE TO BOTH C THE UNDER AND OVERFLOW LIMITS AND THE NORMALIZATION MUST BE C SCALED TO PREVENT OVER OR UNDERFLOW. CUOIK HAS DETERMINED THAT C THE RESULT IS ON SCALE. C----------------------------------------------------------------------- ACW = CABS(CW(2)) ASCLE = 1.0E+3*R1MACH(1)/TOL CSCL = CMPLX(1.0E0,0.0E0) IF (ACW.GT.ASCLE) GO TO 20 CSCL = CMPLX(1.0E0/TOL,0.0E0) GO TO 30 20 CONTINUE ASCLE = 1.0E0/ASCLE IF (ACW.LT.ASCLE) GO TO 30 CSCL = CMPLX(TOL,0.0E0) 30 CONTINUE C1 = CW(1)*CSCL C2 = CW(2)*CSCL ST = Y(1) C----------------------------------------------------------------------- C CINU=CINU*(CONJG(CT)/CABS(CT))*(1.0E0/CABS(CT) PREVENTS C UNDER- OR OVERFLOW PREMATURELY BY SQUARING CABS(CT) C----------------------------------------------------------------------- CT = ZR*(C2+ST*C1) ACT = CABS(CT) RCT = CMPLX(1.0E0/ACT,0.0E0) CT = CONJG(CT)*RCT CINU = CINU*RCT*CT Y(1) = CINU*CSCL IF (N.EQ.1) RETURN DO 40 I=2,N CINU = ST*CINU ST = Y(I) Y(I) = CINU*CSCL 40 CONTINUE RETURN 50 CONTINUE NZ = -1 IF(NW.EQ.(-2)) NZ=-2 RETURN END