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*> \brief \b SGET10
*
* =========== DOCUMENTATION ===========
*
* Online html documentation available at
* http://www.netlib.org/lapack/explore-html/
*
* Definition:
* ===========
*
* SUBROUTINE SGET10( M, N, A, LDA, B, LDB, WORK, RESULT )
*
* .. Scalar Arguments ..
* INTEGER LDA, LDB, M, N
* REAL RESULT
* ..
* .. Array Arguments ..
* REAL A( LDA, * ), B( LDB, * ), WORK( * )
* ..
*
*
*> \par Purpose:
* =============
*>
*> \verbatim
*>
*> SGET10 compares two matrices A and B and computes the ratio
*> RESULT = norm( A - B ) / ( norm(A) * M * EPS )
*> \endverbatim
*
* Arguments:
* ==========
*
*> \param[in] M
*> \verbatim
*> M is INTEGER
*> The number of rows of the matrices A and B.
*> \endverbatim
*>
*> \param[in] N
*> \verbatim
*> N is INTEGER
*> The number of columns of the matrices A and B.
*> \endverbatim
*>
*> \param[in] A
*> \verbatim
*> A is REAL array, dimension (LDA,N)
*> The m by n matrix A.
*> \endverbatim
*>
*> \param[in] LDA
*> \verbatim
*> LDA is INTEGER
*> The leading dimension of the array A. LDA >= max(1,M).
*> \endverbatim
*>
*> \param[in] B
*> \verbatim
*> B is REAL array, dimension (LDB,N)
*> The m by n matrix B.
*> \endverbatim
*>
*> \param[in] LDB
*> \verbatim
*> LDB is INTEGER
*> The leading dimension of the array B. LDB >= max(1,M).
*> \endverbatim
*>
*> \param[out] WORK
*> \verbatim
*> WORK is REAL array, dimension (M)
*> \endverbatim
*>
*> \param[out] RESULT
*> \verbatim
*> RESULT is REAL
*> RESULT = norm( A - B ) / ( norm(A) * M * EPS )
*> \endverbatim
*
* Authors:
* ========
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \date December 2016
*
*> \ingroup single_eig
*
* =====================================================================
SUBROUTINE SGET10( M, N, A, LDA, B, LDB, WORK, RESULT )
*
* -- LAPACK test 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 LDA, LDB, M, N
REAL RESULT
* ..
* .. Array Arguments ..
REAL A( LDA, * ), B( LDB, * ), WORK( * )
* ..
*
* =====================================================================
*
* .. Parameters ..
REAL ONE, ZERO
PARAMETER ( ONE = 1.0E+0, ZERO = 0.0E+0 )
* ..
* .. Local Scalars ..
INTEGER J
REAL ANORM, EPS, UNFL, WNORM
* ..
* .. External Functions ..
REAL SASUM, SLAMCH, SLANGE
EXTERNAL SASUM, SLAMCH, SLANGE
* ..
* .. External Subroutines ..
EXTERNAL SAXPY, SCOPY
* ..
* .. Intrinsic Functions ..
INTRINSIC MAX, MIN, REAL
* ..
* .. Executable Statements ..
*
* Quick return if possible
*
IF( M.LE.0 .OR. N.LE.0 ) THEN
RESULT = ZERO
RETURN
END IF
*
UNFL = SLAMCH( 'Safe minimum' )
EPS = SLAMCH( 'Precision' )
*
WNORM = ZERO
DO 10 J = 1, N
CALL SCOPY( M, A( 1, J ), 1, WORK, 1 )
CALL SAXPY( M, -ONE, B( 1, J ), 1, WORK, 1 )
WNORM = MAX( WNORM, SASUM( N, WORK, 1 ) )
10 CONTINUE
*
ANORM = MAX( SLANGE( '1', M, N, A, LDA, WORK ), UNFL )
*
IF( ANORM.GT.WNORM ) THEN
RESULT = ( WNORM / ANORM ) / ( M*EPS )
ELSE
IF( ANORM.LT.ONE ) THEN
RESULT = ( MIN( WNORM, M*ANORM ) / ANORM ) / ( M*EPS )
ELSE
RESULT = MIN( WNORM / ANORM, REAL( M ) ) / ( M*EPS )
END IF
END IF
*
RETURN
*
* End of SGET10
*
END
|
