148 lines
4.0 KiB
Fortran
148 lines
4.0 KiB
Fortran
*> \brief \b CLA_GERPVGRW multiplies a square real matrix by a complex matrix.
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*
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* =========== DOCUMENTATION ===========
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*
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* Online html documentation available at
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* http://www.netlib.org/lapack/explore-html/
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*
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*> \htmlonly
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*> Download CLA_GERPVGRW + dependencies
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/cla_gerpvgrw.f">
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*> [TGZ]</a>
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/cla_gerpvgrw.f">
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*> [ZIP]</a>
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/cla_gerpvgrw.f">
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*> [TXT]</a>
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*> \endhtmlonly
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*
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* Definition:
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* ===========
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*
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* REAL FUNCTION CLA_GERPVGRW( N, NCOLS, A, LDA, AF, LDAF )
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*
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* .. Scalar Arguments ..
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* INTEGER N, NCOLS, LDA, LDAF
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* ..
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* .. Array Arguments ..
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* COMPLEX A( LDA, * ), AF( LDAF, * )
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* ..
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*
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*
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*> \par Purpose:
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* =============
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*>
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*> \verbatim
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*>
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*>
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*> CLA_GERPVGRW computes the reciprocal pivot growth factor
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*> norm(A)/norm(U). The "max absolute element" norm is used. If this is
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*> much less than 1, the stability of the LU factorization of the
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*> (equilibrated) matrix A could be poor. This also means that the
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*> solution X, estimated condition numbers, and error bounds could be
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*> unreliable.
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*> \endverbatim
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*
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* Arguments:
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* ==========
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*
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*> \param[in] N
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*> \verbatim
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*> N is INTEGER
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*> The number of linear equations, i.e., the order of the
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*> matrix A. N >= 0.
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*> \endverbatim
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*>
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*> \param[in] NCOLS
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*> \verbatim
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*> NCOLS is INTEGER
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*> The number of columns of the matrix A. NCOLS >= 0.
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*> \endverbatim
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*>
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*> \param[in] A
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*> \verbatim
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*> A is COMPLEX array, dimension (LDA,N)
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*> On entry, the N-by-N matrix A.
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*> \endverbatim
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*>
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*> \param[in] LDA
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*> \verbatim
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*> LDA is INTEGER
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*> The leading dimension of the array A. LDA >= max(1,N).
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*> \endverbatim
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*>
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*> \param[in] AF
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*> \verbatim
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*> AF is COMPLEX array, dimension (LDAF,N)
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*> The factors L and U from the factorization
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*> A = P*L*U as computed by CGETRF.
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*> \endverbatim
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*>
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*> \param[in] LDAF
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*> \verbatim
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*> LDAF is INTEGER
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*> The leading dimension of the array AF. LDAF >= max(1,N).
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*> \endverbatim
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*
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* Authors:
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* ========
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*
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*> \author Univ. of Tennessee
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*> \author Univ. of California Berkeley
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*> \author Univ. of Colorado Denver
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*> \author NAG Ltd.
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*
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*> \date September 2012
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*
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*> \ingroup complexGEcomputational
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*
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* =====================================================================
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REAL FUNCTION CLA_GERPVGRW( N, NCOLS, A, LDA, AF, LDAF )
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*
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* -- LAPACK computational routine (version 3.4.2) --
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* -- LAPACK is a software package provided by Univ. of Tennessee, --
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* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
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* September 2012
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*
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* .. Scalar Arguments ..
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INTEGER N, NCOLS, LDA, LDAF
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* ..
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* .. Array Arguments ..
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COMPLEX A( LDA, * ), AF( LDAF, * )
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* ..
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*
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* =====================================================================
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*
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* .. Local Scalars ..
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INTEGER I, J
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REAL AMAX, UMAX, RPVGRW
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COMPLEX ZDUM
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* ..
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* .. Intrinsic Functions ..
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INTRINSIC MAX, MIN, ABS, REAL, AIMAG
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* ..
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* .. Statement Functions ..
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REAL CABS1
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* ..
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* .. Statement Function Definitions ..
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CABS1( ZDUM ) = ABS( REAL( ZDUM ) ) + ABS( AIMAG( ZDUM ) )
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* ..
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* .. Executable Statements ..
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*
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RPVGRW = 1.0
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DO J = 1, NCOLS
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AMAX = 0.0
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UMAX = 0.0
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DO I = 1, N
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AMAX = MAX( CABS1( A( I, J ) ), AMAX )
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END DO
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DO I = 1, J
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UMAX = MAX( CABS1( AF( I, J ) ), UMAX )
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END DO
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IF ( UMAX /= 0.0 ) THEN
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RPVGRW = MIN( AMAX / UMAX, RPVGRW )
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END IF
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END DO
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CLA_GERPVGRW = RPVGRW
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END
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