*> \brief \b SCNRM2 * * =========== DOCUMENTATION =========== * * Online html documentation available at * http://www.netlib.org/lapack/explore-html/ * * Definition: * =========== * * REAL FUNCTION SCNRM2(N,X,INCX) * * .. Scalar Arguments .. * INTEGER INCX,N * .. * .. Array Arguments .. * COMPLEX X(*) * .. * * *> \par Purpose: * ============= *> *> \verbatim *> *> SCNRM2 returns the euclidean norm of a vector via the function *> name, so that *> *> SCNRM2 := sqrt( x**H*x ) *> \endverbatim * * Authors: * ======== * *> \author Univ. of Tennessee *> \author Univ. of California Berkeley *> \author Univ. of Colorado Denver *> \author NAG Ltd. * *> \date December 2016 * *> \ingroup single_blas_level1 * *> \par Further Details: * ===================== *> *> \verbatim *> *> -- This version written on 25-October-1982. *> Modified on 14-October-1993 to inline the call to CLASSQ. *> Sven Hammarling, Nag Ltd. *> \endverbatim *> * ===================================================================== REAL FUNCTION SCNRM2(N,X,INCX) * * -- Reference BLAS level1 routine (version 3.7.0) -- * -- Reference BLAS is a software package provided by Univ. of Tennessee, -- * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- * December 2016 * * .. Scalar Arguments .. INTEGER INCX,N * .. * .. Array Arguments .. COMPLEX X(*) * .. * * ===================================================================== * * .. Parameters .. REAL ONE,ZERO PARAMETER (ONE=1.0E+0,ZERO=0.0E+0) * .. * .. Local Scalars .. REAL NORM,SCALE,SSQ,TEMP INTEGER IX * .. * .. Intrinsic Functions .. INTRINSIC ABS,AIMAG,REAL,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 CLASSQ( N, X, INCX, SCALE, SSQ ) * DO 10 IX = 1,1 + (N-1)*INCX,INCX IF (REAL(X(IX)).NE.ZERO) THEN TEMP = ABS(REAL(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 (AIMAG(X(IX)).NE.ZERO) THEN TEMP = ABS(AIMAG(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 * SCNRM2 = NORM RETURN * * End of SCNRM2. * END