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SUBROUTINE DLADIV( A, B, C, D, P, Q )
* * -- LAPACK auxiliary routine (version 3.2) -- * -- LAPACK is a software package provided by Univ. of Tennessee, -- * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- * November 2006 * * .. Scalar Arguments .. DOUBLE PRECISION A, B, C, D, P, Q * .. * * Purpose * ======= * * DLADIV performs complex division in real arithmetic * * a + i*b * p + i*q = --------- * c + i*d * * The algorithm is due to Robert L. Smith and can be found * in D. Knuth, The art of Computer Programming, Vol.2, p.195 * * Arguments * ========= * * A (input) DOUBLE PRECISION * B (input) DOUBLE PRECISION * C (input) DOUBLE PRECISION * D (input) DOUBLE PRECISION * The scalars a, b, c, and d in the above expression. * * P (output) DOUBLE PRECISION * Q (output) DOUBLE PRECISION * The scalars p and q in the above expression. * * ===================================================================== * * .. Local Scalars .. DOUBLE PRECISION E, F * .. * .. Intrinsic Functions .. INTRINSIC ABS * .. * .. Executable Statements .. * IF( ABS( D ).LT.ABS( C ) ) THEN E = D / C F = C + D*E P = ( A+B*E ) / F Q = ( B-A*E ) / F ELSE E = C / D F = D + C*E P = ( B+A*E ) / F Q = ( -A+B*E ) / F END IF * RETURN * * End of DLADIV * END |