cuchk.f

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      SUBROUTINE cuchk(Y, NZ, ASCLE, TOL)
C***BEGIN PROLOGUE  CUCHK
C***REFER TO CSERI,CUOIK,CUNK1,CUNK2,CUNI1,CUNI2,CKSCL
C
C      Y ENTERS AS A SCALED QUANTITY WHOSE MAGNITUDE IS GREATER THAN
C      EXP(-ALIM)=ASCLE=1.0E+3*R1MACH(1)/TOL. THE TEST IS MADE TO SEE
C      IF THE MAGNITUDE OF THE REAL OR IMAGINARY PART WOULD UNDER FLOW
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  CUCHK
C
      COMPLEX y
      REAL ascle, ss, st, tol, yr, yi
      INTEGER nz
      nz = 0
      yr = REAL(y)
      yi = aimag(y)
      yr = abs(yr)
      yi = abs(yi)
      st = amin1(yr,yi)
      IF (st.GT.ascle) RETURN
      ss = amax1(yr,yi)
      st=st/tol
      IF (ss.LT.st) nz = 1
      RETURN
      END