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40 lines
1.3 KiB
Fortran
40 lines
1.3 KiB
Fortran
*DECK ZUCHK
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SUBROUTINE ZUCHK (YR, YI, NZ, ASCLE, TOL)
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C***BEGIN PROLOGUE ZUCHK
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C***SUBSIDIARY
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C***PURPOSE Subsidiary to SERI, ZUOIK, ZUNK1, ZUNK2, ZUNI1, ZUNI2 and
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C ZKSCL
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C***LIBRARY SLATEC
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C***TYPE ALL (CUCHK-A, ZUCHK-A)
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C***AUTHOR Amos, D. E., (SNL)
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C***DESCRIPTION
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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***SEE ALSO SERI, ZKSCL, ZUNI1, ZUNI2, ZUNK1, ZUNK2, ZUOIK
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C***ROUTINES CALLED (NONE)
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C***REVISION HISTORY (YYMMDD)
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C ?????? DATE WRITTEN
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C 910415 Prologue converted to Version 4.0 format. (BAB)
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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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C***FIRST EXECUTABLE STATEMENT ZUCHK
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NZ = 0
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WR = ABS(YR)
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WI = ABS(YI)
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ST = MIN(WR,WI)
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IF (ST.GT.ASCLE) RETURN
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SS = MAX(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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