*> \brief \b SRSCL multiplies a vector by the reciprocal of a real scalar. * * =========== DOCUMENTATION =========== * * Online html documentation available at * http://www.netlib.org/lapack/explore-html/ * *> \htmlonly *> Download SRSCL + dependencies *> *> [TGZ] *> *> [ZIP] *> *> [TXT] *> \endhtmlonly * * Definition: * =========== * * SUBROUTINE SRSCL( N, SA, SX, INCX ) * * .. Scalar Arguments .. * INTEGER INCX, N * REAL SA * .. * .. Array Arguments .. * REAL SX( * ) * .. * * *> \par Purpose: * ============= *> *> \verbatim *> *> SRSCL multiplies an n-element real vector x by the real scalar 1/a. *> This is done without overflow or underflow as long as *> the final result x/a does not overflow or underflow. *> \endverbatim * * Arguments: * ========== * *> \param[in] N *> \verbatim *> N is INTEGER *> The number of components of the vector x. *> \endverbatim *> *> \param[in] SA *> \verbatim *> SA is REAL *> The scalar a which is used to divide each component of x. *> SA must be >= 0, or the subroutine will divide by zero. *> \endverbatim *> *> \param[in,out] SX *> \verbatim *> SX is REAL array, dimension *> (1+(N-1)*abs(INCX)) *> The n-element vector x. *> \endverbatim *> *> \param[in] INCX *> \verbatim *> INCX is INTEGER *> The increment between successive values of the vector SX. *> > 0: SX(1) = X(1) and SX(1+(i-1)*INCX) = x(i), 1< i<= n *> \endverbatim * * Authors: * ======== * *> \author Univ. of Tennessee *> \author Univ. of California Berkeley *> \author Univ. of Colorado Denver *> \author NAG Ltd. * *> \date December 2016 * *> \ingroup realOTHERauxiliary * * ===================================================================== SUBROUTINE SRSCL( N, SA, SX, INCX ) * * -- LAPACK auxiliary routine (version 3.7.0) -- * -- LAPACK 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 REAL SA * .. * .. Array Arguments .. REAL SX( * ) * .. * * ===================================================================== * * .. Parameters .. REAL ONE, ZERO PARAMETER ( ONE = 1.0E+0, ZERO = 0.0E+0 ) * .. * .. Local Scalars .. LOGICAL DONE REAL BIGNUM, CDEN, CDEN1, CNUM, CNUM1, MUL, SMLNUM * .. * .. External Functions .. REAL SLAMCH EXTERNAL SLAMCH * .. * .. External Subroutines .. EXTERNAL SLABAD, SSCAL * .. * .. Intrinsic Functions .. INTRINSIC ABS * .. * .. Executable Statements .. * * Quick return if possible * IF( N.LE.0 ) \$ RETURN * * Get machine parameters * SMLNUM = SLAMCH( 'S' ) BIGNUM = ONE / SMLNUM CALL SLABAD( SMLNUM, BIGNUM ) * * Initialize the denominator to SA and the numerator to 1. * CDEN = SA CNUM = ONE * 10 CONTINUE CDEN1 = CDEN*SMLNUM CNUM1 = CNUM / BIGNUM IF( ABS( CDEN1 ).GT.ABS( CNUM ) .AND. CNUM.NE.ZERO ) THEN * * Pre-multiply X by SMLNUM if CDEN is large compared to CNUM. * MUL = SMLNUM DONE = .FALSE. CDEN = CDEN1 ELSE IF( ABS( CNUM1 ).GT.ABS( CDEN ) ) THEN * * Pre-multiply X by BIGNUM if CDEN is small compared to CNUM. * MUL = BIGNUM DONE = .FALSE. CNUM = CNUM1 ELSE * * Multiply X by CNUM / CDEN and return. * MUL = CNUM / CDEN DONE = .TRUE. END IF * * Scale the vector X by MUL * CALL SSCAL( N, MUL, SX, INCX ) * IF( .NOT.DONE ) \$ GO TO 10 * RETURN * * End of SRSCL * END