DOUBLE PRECISION FUNCTION ZTZT02( M, N, AF, LDA, TAU, WORK, \$ LWORK ) * * -- LAPACK test routine (version 3.1) -- * Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. * November 2006 * * .. Scalar Arguments .. INTEGER LDA, LWORK, M, N * .. * .. Array Arguments .. COMPLEX*16 AF( LDA, * ), TAU( * ), WORK( LWORK ) * .. * * Purpose * ======= * * ZTZT02 returns * || I - Q'*Q || / ( M * eps) * where the matrix Q is defined by the Householder transformations * generated by ZTZRQF. * * Arguments * ========= * * M (input) INTEGER * The number of rows of the matrix AF. * * N (input) INTEGER * The number of columns of the matrix AF. * * AF (input) COMPLEX*16 array, dimension (LDA,N) * The output of ZTZRQF. * * LDA (input) INTEGER * The leading dimension of the array AF. * * TAU (input) COMPLEX*16 array, dimension (M) * Details of the Householder transformations as returned by * ZTZRQF. * * WORK (workspace) COMPLEX*16 array, dimension (LWORK) * * LWORK (input) INTEGER * length of WORK array. Must be >= N*N+N * * ===================================================================== * * .. Parameters .. DOUBLE PRECISION ZERO, ONE PARAMETER ( ZERO = 0.0D0, ONE = 1.0D0 ) * .. * .. Local Scalars .. INTEGER I * .. * .. Local Arrays .. DOUBLE PRECISION RWORK( 1 ) * .. * .. External Functions .. DOUBLE PRECISION DLAMCH, ZLANGE EXTERNAL DLAMCH, ZLANGE * .. * .. External Subroutines .. EXTERNAL XERBLA, ZLASET, ZLATZM * .. * .. Intrinsic Functions .. INTRINSIC DBLE, DCMPLX, DCONJG, MAX * .. * .. Executable Statements .. * ZTZT02 = ZERO * IF( LWORK.LT.N*N+N ) THEN CALL XERBLA( 'ZTZT02', 7 ) RETURN END IF * * Quick return if possible * IF( M.LE.0 .OR. N.LE.0 ) \$ RETURN * * Q := I * CALL ZLASET( 'Full', N, N, DCMPLX( ZERO ), DCMPLX( ONE ), WORK, \$ N ) * * Q := P(1) * ... * P(m) * Q * DO 10 I = M, 1, -1 CALL ZLATZM( 'Left', N-M+1, N, AF( I, M+1 ), LDA, TAU( I ), \$ WORK( I ), WORK( M+1 ), N, WORK( N*N+1 ) ) 10 CONTINUE * * Q := P(m)' * ... * P(1)' * Q * DO 20 I = 1, M CALL ZLATZM( 'Left', N-M+1, N, AF( I, M+1 ), LDA, \$ DCONJG( TAU( I ) ), WORK( I ), WORK( M+1 ), N, \$ WORK( N*N+1 ) ) 20 CONTINUE * * Q := Q - I * DO 30 I = 1, N WORK( ( I-1 )*N+I ) = WORK( ( I-1 )*N+I ) - ONE 30 CONTINUE * ZTZT02 = ZLANGE( 'One-norm', N, N, WORK, N, RWORK ) / \$ ( DLAMCH( 'Epsilon' )*DBLE( MAX( M, N ) ) ) RETURN * * End of ZTZT02 * END