121 lines
3.3 KiB
FortranFixed
121 lines
3.3 KiB
FortranFixed
SUBROUTINE CGET03( N, A, LDA, AINV, LDAINV, WORK, LDWORK, RWORK,
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$ RCOND, RESID )
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*
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* -- LAPACK test routine (version 3.1) --
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* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
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* November 2006
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*
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* .. Scalar Arguments ..
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INTEGER LDA, LDAINV, LDWORK, N
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REAL RCOND, RESID
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* ..
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* .. Array Arguments ..
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REAL RWORK( * )
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COMPLEX A( LDA, * ), AINV( LDAINV, * ),
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$ WORK( LDWORK, * )
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* ..
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*
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* Purpose
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* =======
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*
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* CGET03 computes the residual for a general matrix times its inverse:
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* norm( I - AINV*A ) / ( N * norm(A) * norm(AINV) * EPS ),
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* where EPS is the machine epsilon.
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*
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* Arguments
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* ==========
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*
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* N (input) INTEGER
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* The number of rows and columns of the matrix A. N >= 0.
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*
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* A (input) COMPLEX array, dimension (LDA,N)
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* The original N x N matrix A.
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*
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* LDA (input) INTEGER
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* The leading dimension of the array A. LDA >= max(1,N).
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*
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* AINV (input) COMPLEX array, dimension (LDAINV,N)
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* The inverse of the matrix A.
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*
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* LDAINV (input) INTEGER
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* The leading dimension of the array AINV. LDAINV >= max(1,N).
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*
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* WORK (workspace) COMPLEX array, dimension (LDWORK,N)
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*
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* LDWORK (input) INTEGER
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* The leading dimension of the array WORK. LDWORK >= max(1,N).
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*
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* RWORK (workspace) REAL array, dimension (N)
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*
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* RCOND (output) REAL
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* The reciprocal of the condition number of A, computed as
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* ( 1/norm(A) ) / norm(AINV).
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*
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* RESID (output) REAL
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* norm(I - AINV*A) / ( N * norm(A) * norm(AINV) * EPS )
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*
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* =====================================================================
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*
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* .. Parameters ..
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REAL ZERO, ONE
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PARAMETER ( ZERO = 0.0E+0, ONE = 1.0E+0 )
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COMPLEX CZERO, CONE
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PARAMETER ( CZERO = ( 0.0E+0, 0.0E+0 ),
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$ CONE = ( 1.0E+0, 0.0E+0 ) )
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* ..
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* .. Local Scalars ..
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INTEGER I
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REAL AINVNM, ANORM, EPS
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* ..
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* .. External Functions ..
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REAL CLANGE, SLAMCH
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EXTERNAL CLANGE, SLAMCH
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* ..
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* .. External Subroutines ..
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EXTERNAL CGEMM
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* ..
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* .. Intrinsic Functions ..
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INTRINSIC REAL
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* ..
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* .. Executable Statements ..
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*
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* Quick exit if N = 0.
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*
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IF( N.LE.0 ) THEN
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RCOND = ONE
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RESID = ZERO
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RETURN
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END IF
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*
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* Exit with RESID = 1/EPS if ANORM = 0 or AINVNM = 0.
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*
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EPS = SLAMCH( 'Epsilon' )
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ANORM = CLANGE( '1', N, N, A, LDA, RWORK )
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AINVNM = CLANGE( '1', N, N, AINV, LDAINV, RWORK )
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IF( ANORM.LE.ZERO .OR. AINVNM.LE.ZERO ) THEN
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RCOND = ZERO
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RESID = ONE / EPS
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RETURN
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END IF
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RCOND = ( ONE/ANORM ) / AINVNM
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*
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* Compute I - A * AINV
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*
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CALL CGEMM( 'No transpose', 'No transpose', N, N, N, -CONE,
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$ AINV, LDAINV, A, LDA, CZERO, WORK, LDWORK )
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DO 10 I = 1, N
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WORK( I, I ) = CONE + WORK( I, I )
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10 CONTINUE
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*
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* Compute norm(I - AINV*A) / (N * norm(A) * norm(AINV) * EPS)
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*
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RESID = CLANGE( '1', N, N, WORK, LDWORK, RWORK )
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*
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RESID = ( ( RESID*RCOND )/EPS ) / REAL( N )
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*
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RETURN
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*
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* End of CGET03
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*
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END
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