| 123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263 |
- *DECK ZS1S2
- SUBROUTINE ZS1S2 (ZRR, ZRI, S1R, S1I, S2R, S2I, NZ, ASCLE, ALIM,
- + IUF)
- C***BEGIN PROLOGUE ZS1S2
- C***SUBSIDIARY
- C***PURPOSE Subsidiary to ZAIRY and ZBESK
- C***LIBRARY SLATEC
- C***TYPE ALL (CS1S2-A, ZS1S2-A)
- C***AUTHOR Amos, D. E., (SNL)
- C***DESCRIPTION
- C
- C ZS1S2 TESTS FOR A POSSIBLE UNDERFLOW RESULTING FROM THE
- C ADDITION OF THE I AND K FUNCTIONS IN THE ANALYTIC CON-
- C TINUATION FORMULA WHERE S1=K FUNCTION AND S2=I FUNCTION.
- C ON KODE=1 THE I AND K FUNCTIONS ARE DIFFERENT ORDERS OF
- C MAGNITUDE, BUT FOR KODE=2 THEY CAN BE OF THE SAME ORDER
- C OF MAGNITUDE AND THE MAXIMUM MUST BE AT LEAST ONE
- C PRECISION ABOVE THE UNDERFLOW LIMIT.
- C
- C***SEE ALSO ZAIRY, ZBESK
- C***ROUTINES CALLED ZABS, ZEXP, ZLOG
- C***REVISION HISTORY (YYMMDD)
- C 830501 DATE WRITTEN
- C 910415 Prologue converted to Version 4.0 format. (BAB)
- C 930122 Added ZEXP and ZLOG to EXTERNAL statement. (RWC)
- C***END PROLOGUE ZS1S2
- C COMPLEX CZERO,C1,S1,S1D,S2,ZR
- DOUBLE PRECISION AA, ALIM, ALN, ASCLE, AS1, AS2, C1I, C1R, S1DI,
- * S1DR, S1I, S1R, S2I, S2R, ZEROI, ZEROR, ZRI, ZRR, ZABS
- INTEGER IUF, IDUM, NZ
- EXTERNAL ZABS, ZEXP, ZLOG
- DATA ZEROR,ZEROI / 0.0D0 , 0.0D0 /
- C***FIRST EXECUTABLE STATEMENT ZS1S2
- NZ = 0
- AS1 = ZABS(S1R,S1I)
- AS2 = ZABS(S2R,S2I)
- IF (S1R.EQ.0.0D0 .AND. S1I.EQ.0.0D0) GO TO 10
- IF (AS1.EQ.0.0D0) GO TO 10
- ALN = -ZRR - ZRR + LOG(AS1)
- S1DR = S1R
- S1DI = S1I
- S1R = ZEROR
- S1I = ZEROI
- AS1 = ZEROR
- IF (ALN.LT.(-ALIM)) GO TO 10
- CALL ZLOG(S1DR, S1DI, C1R, C1I, IDUM)
- C1R = C1R - ZRR - ZRR
- C1I = C1I - ZRI - ZRI
- CALL ZEXP(C1R, C1I, S1R, S1I)
- AS1 = ZABS(S1R,S1I)
- IUF = IUF + 1
- 10 CONTINUE
- AA = MAX(AS1,AS2)
- IF (AA.GT.ASCLE) RETURN
- S1R = ZEROR
- S1I = ZEROI
- S2R = ZEROR
- S2I = ZEROI
- NZ = 1
- IUF = 0
- RETURN
- END
|
