root / src / blas / crotg.f @ 10
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SUBROUTINE CROTG(CA,CB,C,S) |
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* .. Scalar Arguments .. |
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COMPLEX CA,CB,S |
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REAL C |
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* .. |
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* |
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* Purpose |
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* ======= |
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* |
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* CROTG determines a complex Givens rotation. |
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* |
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* .. Local Scalars .. |
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COMPLEX ALPHA |
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REAL NORM,SCALE |
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* .. |
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* .. Intrinsic Functions .. |
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INTRINSIC CABS,CONJG,SQRT |
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* .. |
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IF (CABS(CA).NE.0.) GO TO 10 |
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C = 0. |
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S = (1.,0.) |
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CA = CB |
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GO TO 20 |
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10 CONTINUE |
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SCALE = CABS(CA) + CABS(CB) |
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NORM = SCALE*SQRT((CABS(CA/SCALE))**2+ (CABS(CB/SCALE))**2) |
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ALPHA = CA/CABS(CA) |
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C = CABS(CA)/NORM |
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S = ALPHA*CONJG(CB)/NORM |
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CA = ALPHA*NORM |
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20 CONTINUE |
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RETURN |
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END |