*> \brief \b DZNRM2 * * =========== DOCUMENTATION =========== * * Online html documentation available at * http://www.netlib.org/lapack/explore-html/ * * Definition: * =========== * * DOUBLE PRECISION FUNCTION DZNRM2(N,X,INCX) * * .. Scalar Arguments .. * INTEGER INCX,N * .. * .. Array Arguments .. * COMPLEX*16 X(*) * .. * * *> \par Purpose: * ============= *> *> \verbatim *> *> DZNRM2 returns the euclidean norm of a vector via the function *> name, so that *> *> DZNRM2 := sqrt( x**H*x ) *> \endverbatim * * Arguments: * ========== * *> \param[in] N *> \verbatim *> N is INTEGER *> number of elements in input vector(s) *> \endverbatim *> *> \param[in] X *> \verbatim *> X is COMPLEX*16 array, dimension (N) *> complex vector with N elements *> \endverbatim *> *> \param[in] INCX *> \verbatim *> INCX is INTEGER *> storage spacing between elements of X *> \endverbatim * * Authors: * ======== * *> \author Univ. of Tennessee *> \author Univ. of California Berkeley *> \author Univ. of Colorado Denver *> \author NAG Ltd. * *> \date November 2017 * *> \ingroup double_blas_level1 * *> \par Further Details: * ===================== *> *> \verbatim *> *> -- This version written on 25-October-1982. *> Modified on 14-October-1993 to inline the call to ZLASSQ. *> Sven Hammarling, Nag Ltd. *> \endverbatim *> * ===================================================================== DOUBLE PRECISION FUNCTION DZNRM2(N,X,INCX) * * -- Reference BLAS level1 routine (version 3.8.0) -- * -- Reference BLAS is a software package provided by Univ. of Tennessee, -- * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- * November 2017 * * .. Scalar Arguments .. INTEGER INCX,N * .. * .. Array Arguments .. COMPLEX*16 X(*) * .. * * ===================================================================== * * .. Parameters .. DOUBLE PRECISION ONE,ZERO PARAMETER (ONE=1.0D+0,ZERO=0.0D+0) * .. * .. Local Scalars .. DOUBLE PRECISION NORM,SCALE,SSQ,TEMP INTEGER IX * .. * .. Intrinsic Functions .. INTRINSIC ABS,DBLE,DIMAG,SQRT * .. IF (N.LT.1 .OR. INCX.LT.1) THEN NORM = ZERO ELSE SCALE = ZERO SSQ = ONE * The following loop is equivalent to this call to the LAPACK * auxiliary routine: * CALL ZLASSQ( N, X, INCX, SCALE, SSQ ) * DO 10 IX = 1,1 + (N-1)*INCX,INCX IF (DBLE(X(IX)).NE.ZERO) THEN TEMP = ABS(DBLE(X(IX))) IF (SCALE.LT.TEMP) THEN SSQ = ONE + SSQ* (SCALE/TEMP)**2 SCALE = TEMP ELSE SSQ = SSQ + (TEMP/SCALE)**2 END IF END IF IF (DIMAG(X(IX)).NE.ZERO) THEN TEMP = ABS(DIMAG(X(IX))) IF (SCALE.LT.TEMP) THEN SSQ = ONE + SSQ* (SCALE/TEMP)**2 SCALE = TEMP ELSE SSQ = SSQ + (TEMP/SCALE)**2 END IF END IF 10 CONTINUE NORM = SCALE*SQRT(SSQ) END IF * DZNRM2 = NORM RETURN * * End of DZNRM2. * END