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SUBROUTINE DGET10( M, N, A, LDA, B, LDB, WORK, RESULT )
*
* -- LAPACK test routine (version 3.0) --
* Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
* Courant Institute, Argonne National Lab, and Rice University
* February 29, 1992
*
* .. Scalar Arguments ..
INTEGER LDA, LDB, M, N
DOUBLE PRECISION RESULT
* ..
* .. Array Arguments ..
DOUBLE PRECISION A( LDA, * ), B( LDB, * ), WORK( * )
* ..
*
* Purpose
* =======
*
* DGET10 compares two matrices A and B and computes the ratio
* RESULT = norm( A - B ) / ( norm(A) * M * EPS )
*
* Arguments
* =========
*
* M (input) INTEGER
* The number of rows of the matrices A and B.
*
* N (input) INTEGER
* The number of columns of the matrices A and B.
*
* A (input) DOUBLE PRECISION array, dimension (LDA,N)
* The m by n matrix A.
*
* LDA (input) INTEGER
* The leading dimension of the array A. LDA >= max(1,M).
*
* B (input) DOUBLE PRECISION array, dimension (LDB,N)
* The m by n matrix B.
*
* LDB (input) INTEGER
* The leading dimension of the array B. LDB >= max(1,M).
*
* WORK (workspace) DOUBLE PRECISION array, dimension (M)
*
* RESULT (output) DOUBLE PRECISION
* RESULT = norm( A - B ) / ( norm(A) * M * EPS )
*
* =====================================================================
*
* .. Parameters ..
DOUBLE PRECISION ONE, ZERO
PARAMETER ( ONE = 1.0D+0, ZERO = 0.0D+0 )
* ..
* .. Local Scalars ..
INTEGER J
DOUBLE PRECISION ANORM, EPS, UNFL, WNORM
* ..
* .. External Functions ..
DOUBLE PRECISION DASUM, DLAMCH, DLANGE
EXTERNAL DASUM, DLAMCH, DLANGE
* ..
* .. External Subroutines ..
EXTERNAL DAXPY, DCOPY
* ..
* .. Intrinsic Functions ..
INTRINSIC DBLE, MAX, MIN
* ..
* .. Executable Statements ..
*
* Quick return if possible
*
IF( M.LE.0 .OR. N.LE.0 ) THEN
RESULT = ZERO
RETURN
END IF
*
UNFL = DLAMCH( 'Safe minimum' )
EPS = DLAMCH( 'Precision' )
*
WNORM = ZERO
DO 10 J = 1, N
CALL DCOPY( M, A( 1, J ), 1, WORK, 1 )
CALL DAXPY( M, -ONE, B( 1, J ), 1, WORK, 1 )
WNORM = MAX( WNORM, DASUM( N, WORK, 1 ) )
10 CONTINUE
*
ANORM = MAX( DLANGE( '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, DBLE( M ) ) / ( M*EPS )
END IF
END IF
*
RETURN
*
* End of DGET10
*
END
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