29 lines
950 B
FortranFixed
29 lines
950 B
FortranFixed
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SUBROUTINE ZUCHK(YR, YI, NZ, ASCLE, TOL)
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C***BEGIN PROLOGUE ZUCHK
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C***REFER TO ZSERI,ZUOIK,ZUNK1,ZUNK2,ZUNI1,ZUNI2,ZKSCL
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C
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C Y ENTERS AS A SCALED QUANTITY WHOSE MAGNITUDE IS GREATER THAN
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C EXP(-ALIM)=ASCLE=1.0E+3*D1MACH(1)/TOL. THE TEST IS MADE TO SEE
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C IF THE MAGNITUDE OF THE REAL OR IMAGINARY PART WOULD UNDERFLOW
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C WHEN Y IS SCALED (BY TOL) TO ITS PROPER VALUE. Y IS ACCEPTED
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C IF THE UNDERFLOW IS AT LEAST ONE PRECISION BELOW THE MAGNITUDE
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C OF THE LARGEST COMPONENT; OTHERWISE THE PHASE ANGLE DOES NOT HAVE
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C ABSOLUTE ACCURACY AND AN UNDERFLOW IS ASSUMED.
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C
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C***ROUTINES CALLED (NONE)
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C***END PROLOGUE ZUCHK
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C
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C COMPLEX Y
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DOUBLE PRECISION ASCLE, SS, ST, TOL, WR, WI, YR, YI
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INTEGER NZ
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NZ = 0
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WR = DABS(YR)
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WI = DABS(YI)
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ST = DMIN1(WR,WI)
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IF (ST.GT.ASCLE) RETURN
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SS = DMAX1(WR,WI)
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ST = ST/TOL
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IF (SS.LT.ST) NZ = 1
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RETURN
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END
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