2019-03-20 12:25:42 +02:00
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SUBROUTINE AZSQRT(AR, AI, BR, BI)
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C***BEGIN PROLOGUE AZSQRT
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2019-03-19 16:42:47 +02:00
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C***REFER TO ZBESH,ZBESI,ZBESJ,ZBESK,ZBESY,ZAIRY,ZBIRY
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C
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C DOUBLE PRECISION COMPLEX SQUARE ROOT, B=CSQRT(A)
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C
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2019-03-20 12:25:42 +02:00
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C***ROUTINES CALLED AZABS
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C***END PROLOGUE AZSQRT
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2019-03-19 16:42:47 +02:00
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DOUBLE PRECISION AR, AI, BR, BI, ZM, DTHETA, DPI, DRT
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2019-03-20 12:25:42 +02:00
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DOUBLE PRECISION AZABS
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2019-03-19 16:42:47 +02:00
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DATA DRT , DPI / 7.071067811865475244008443621D-1,
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1 3.141592653589793238462643383D+0/
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2019-03-20 12:25:42 +02:00
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ZM = AZABS(AR,AI)
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2019-03-19 16:42:47 +02:00
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ZM = DSQRT(ZM)
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IF (AR.EQ.0.0D+0) GO TO 10
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IF (AI.EQ.0.0D+0) GO TO 20
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DTHETA = DATAN(AI/AR)
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IF (DTHETA.LE.0.0D+0) GO TO 40
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IF (AR.LT.0.0D+0) DTHETA = DTHETA - DPI
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GO TO 50
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10 IF (AI.GT.0.0D+0) GO TO 60
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IF (AI.LT.0.0D+0) GO TO 70
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BR = 0.0D+0
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BI = 0.0D+0
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RETURN
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20 IF (AR.GT.0.0D+0) GO TO 30
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BR = 0.0D+0
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BI = DSQRT(DABS(AR))
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RETURN
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30 BR = DSQRT(AR)
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BI = 0.0D+0
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RETURN
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40 IF (AR.LT.0.0D+0) DTHETA = DTHETA + DPI
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50 DTHETA = DTHETA*0.5D+0
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BR = ZM*DCOS(DTHETA)
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BI = ZM*DSIN(DTHETA)
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RETURN
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60 BR = ZM*DRT
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BI = ZM*DRT
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RETURN
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70 BR = ZM*DRT
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BI = -ZM*DRT
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RETURN
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END
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