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| 1 | SUBROUTINE CROTG(CA,CB,C,S) |
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| 2 | * .. Scalar Arguments .. |
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| 3 | COMPLEX CA,CB,S |
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| 4 | REAL C |
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| 5 | * .. |
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| 6 | * |
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| 7 | * Purpose |
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| 8 | * ======= |
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| 9 | * |
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| 10 | * CROTG determines a complex Givens rotation. |
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| 11 | * |
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| 12 | * .. Local Scalars .. |
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| 13 | COMPLEX ALPHA |
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| 14 | REAL NORM,SCALE |
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| 15 | * .. |
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| 16 | * .. Intrinsic Functions .. |
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| 17 | INTRINSIC CABS,CONJG,SQRT |
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| 18 | * .. |
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| 19 | IF (CABS(CA).NE.0.) GO TO 10 |
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| 20 | C = 0. |
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| 21 | S = (1.,0.) |
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| 22 | CA = CB |
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| 23 | GO TO 20 |
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| 24 | 10 CONTINUE |
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| 25 | SCALE = CABS(CA) + CABS(CB) |
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| 26 | NORM = SCALE*SQRT((CABS(CA/SCALE))**2+ (CABS(CB/SCALE))**2) |
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| 27 | ALPHA = CA/CABS(CA) |
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| 28 | C = CABS(CA)/NORM |
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| 29 | S = ALPHA*CONJG(CB)/NORM |
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| 30 | CA = ALPHA*NORM |
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| 31 | 20 CONTINUE |
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| 32 | RETURN |
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| 33 | END |
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