124 lines
3.2 KiB
FortranFixed
124 lines
3.2 KiB
FortranFixed
DOUBLE PRECISION FUNCTION DTZT01( M, N, A, 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 A( LDA, * ), AF( LDA, * ), TAU( * ),
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$ 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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* DTZT01 returns
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* || A - R*Q || / ( M * eps * ||A|| )
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* for an upper trapezoidal A that was factored with 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 matrices A and AF.
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*
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* N (input) INTEGER
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* The number of columns of the matrices A and AF.
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*
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* A (input) DOUBLE PRECISION array, dimension (LDA,N)
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* The original upper trapezoidal M by N matrix A.
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*
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* AF (input) DOUBLE PRECISION array, dimension (LDA,N)
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* The output of DTZRQF for input matrix A.
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* The lower triangle is not referenced.
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*
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* LDA (input) INTEGER
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* The leading dimension of the arrays A and 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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* The length of the array WORK. LWORK >= m*n + m.
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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, J
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DOUBLE PRECISION NORMA
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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 DAXPY, 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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DTZT01 = ZERO
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*
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IF( LWORK.LT.M*N+M ) THEN
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CALL XERBLA( 'DTZT01', 8 )
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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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NORMA = DLANGE( 'One-norm', M, N, A, LDA, RWORK )
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*
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* Copy upper triangle R
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*
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CALL DLASET( 'Full', M, N, ZERO, ZERO, WORK, M )
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DO 20 J = 1, M
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DO 10 I = 1, J
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WORK( ( J-1 )*M+I ) = AF( I, J )
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10 CONTINUE
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20 CONTINUE
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*
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* R = R * P(1) * ... *P(m)
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*
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DO 30 I = 1, M
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CALL DLATZM( 'Right', I, N-M+1, AF( I, M+1 ), LDA, TAU( I ),
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$ WORK( ( I-1 )*M+1 ), WORK( M*M+1 ), M,
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$ WORK( M*N+1 ) )
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30 CONTINUE
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*
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* R = R - A
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*
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DO 40 I = 1, N
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CALL DAXPY( M, -ONE, A( 1, I ), 1, WORK( ( I-1 )*M+1 ), 1 )
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40 CONTINUE
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*
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DTZT01 = DLANGE( 'One-norm', M, N, WORK, M, RWORK )
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*
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DTZT01 = DTZT01 / ( DLAMCH( 'Epsilon' )*DBLE( MAX( M, N ) ) )
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IF( NORMA.NE.ZERO )
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$ DTZT01 = DTZT01 / NORMA
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*
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RETURN
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*
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* End of DTZT01
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*
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END
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