114 lines
2.8 KiB
FortranFixed
114 lines
2.8 KiB
FortranFixed
DOUBLE PRECISION FUNCTION DTZT02( M, N, AF, LDA, TAU, WORK,
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$ LWORK )
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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, LWORK, M, N
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* ..
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* .. Array Arguments ..
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DOUBLE PRECISION AF( LDA, * ), TAU( * ), WORK( LWORK )
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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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* DTZT02 returns
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* || I - Q'*Q || / ( M * eps)
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* where the matrix Q is defined by the Householder transformations
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* generated by DTZRQF.
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*
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* Arguments
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* =========
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*
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* M (input) INTEGER
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* The number of rows of the matrix AF.
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*
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* N (input) INTEGER
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* The number of columns of the matrix AF.
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*
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* AF (input) DOUBLE PRECISION array, dimension (LDA,N)
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* The output of DTZRQF.
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*
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* LDA (input) INTEGER
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* The leading dimension of the array AF.
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*
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* TAU (input) DOUBLE PRECISION array, dimension (M)
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* Details of the Householder transformations as returned by
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* DTZRQF.
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*
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* WORK (workspace) DOUBLE PRECISION array, dimension (LWORK)
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*
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* LWORK (input) INTEGER
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* length of WORK array. Must be >= N*N+N
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*
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* =====================================================================
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*
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* .. Parameters ..
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DOUBLE PRECISION ZERO, ONE
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PARAMETER ( ZERO = 0.0D0, ONE = 1.0D0 )
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* ..
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* .. Local Scalars ..
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INTEGER I
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* ..
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* .. Local Arrays ..
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DOUBLE PRECISION RWORK( 1 )
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* ..
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* .. External Functions ..
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DOUBLE PRECISION DLAMCH, DLANGE
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EXTERNAL DLAMCH, DLANGE
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* ..
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* .. External Subroutines ..
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EXTERNAL DLASET, DLATZM, XERBLA
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* ..
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* .. Intrinsic Functions ..
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INTRINSIC DBLE, MAX
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* ..
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* .. Executable Statements ..
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*
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DTZT02 = ZERO
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*
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IF( LWORK.LT.N*N+N ) THEN
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CALL XERBLA( 'DTZT02', 7 )
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RETURN
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END IF
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*
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* Quick return if possible
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*
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IF( M.LE.0 .OR. N.LE.0 )
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$ RETURN
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*
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* Q := I
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*
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CALL DLASET( 'Full', N, N, ZERO, ONE, WORK, N )
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*
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* Q := P(1) * ... * P(m) * Q
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*
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DO 10 I = M, 1, -1
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CALL DLATZM( 'Left', N-M+1, N, AF( I, M+1 ), LDA, TAU( I ),
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$ WORK( I ), WORK( M+1 ), N, WORK( N*N+1 ) )
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10 CONTINUE
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*
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* Q := P(m) * ... * P(1) * Q
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*
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DO 20 I = 1, M
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CALL DLATZM( 'Left', N-M+1, N, AF( I, M+1 ), LDA, TAU( I ),
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$ WORK( I ), WORK( M+1 ), N, WORK( N*N+1 ) )
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20 CONTINUE
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*
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* Q := Q - I
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*
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DO 30 I = 1, N
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WORK( ( I-1 )*N+I ) = WORK( ( I-1 )*N+I ) - ONE
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30 CONTINUE
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*
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DTZT02 = DLANGE( 'One-norm', N, N, WORK, N, RWORK ) /
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$ ( DLAMCH( 'Epsilon' )*DBLE( MAX( M, N ) ) )
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RETURN
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*
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* End of DTZT02
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*
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END
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