1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
|
SUBROUTINE ZUCHK(YR, YI, NZ, ASCLE, TOL)
C***BEGIN PROLOGUE ZUCHK
C***REFER TO ZSERI,ZUOIK,ZUNK1,ZUNK2,ZUNI1,ZUNI2,ZKSCL
C
C Y ENTERS AS A SCALED QUANTITY WHOSE MAGNITUDE IS GREATER THAN
C EXP(-ALIM)=ASCLE=1.0E+3*D1MACH(1)/TOL. THE TEST IS MADE TO SEE
C IF THE MAGNITUDE OF THE REAL OR IMAGINARY PART WOULD UNDERFLOW
C WHEN Y IS SCALED (BY TOL) TO ITS PROPER VALUE. Y IS ACCEPTED
C IF THE UNDERFLOW IS AT LEAST ONE PRECISION BELOW THE MAGNITUDE
C OF THE LARGEST COMPONENT; OTHERWISE THE PHASE ANGLE DOES NOT HAVE
C ABSOLUTE ACCURACY AND AN UNDERFLOW IS ASSUMED.
C
C***ROUTINES CALLED (NONE)
C***END PROLOGUE ZUCHK
C
C COMPLEX Y
DOUBLE PRECISION ASCLE, SS, ST, TOL, WR, WI, YR, YI
INTEGER NZ
NZ = 0
WR = DABS(YR)
WI = DABS(YI)
ST = DMIN1(WR,WI)
IF (ST.GT.ASCLE) RETURN
SS = DMAX1(WR,WI)
ST = ST/TOL
IF (SS.LT.ST) NZ = 1
RETURN
END
|
