1*> \brief \b STZT02 2* 3* =========== DOCUMENTATION =========== 4* 5* Online html documentation available at 6* http://www.netlib.org/lapack/explore-html/ 7* 8* Definition: 9* =========== 10* 11* REAL FUNCTION STZT02( M, N, AF, LDA, TAU, WORK, 12* LWORK ) 13* 14* .. Scalar Arguments .. 15* INTEGER LDA, LWORK, M, N 16* .. 17* .. Array Arguments .. 18* REAL AF( LDA, * ), TAU( * ), WORK( LWORK ) 19* .. 20* 21* 22*> \par Purpose: 23* ============= 24*> 25*> \verbatim 26*> 27*> STZT02 returns 28*> || I - Q'*Q || / ( M * eps) 29*> where the matrix Q is defined by the Householder transformations 30*> generated by STZRQF. 31*> \endverbatim 32* 33* Arguments: 34* ========== 35* 36*> \param[in] M 37*> \verbatim 38*> M is INTEGER 39*> The number of rows of the matrix AF. 40*> \endverbatim 41*> 42*> \param[in] N 43*> \verbatim 44*> N is INTEGER 45*> The number of columns of the matrix AF. 46*> \endverbatim 47*> 48*> \param[in] AF 49*> \verbatim 50*> AF is REAL array, dimension (LDA,N) 51*> The output of STZRQF. 52*> \endverbatim 53*> 54*> \param[in] LDA 55*> \verbatim 56*> LDA is INTEGER 57*> The leading dimension of the array AF. 58*> \endverbatim 59*> 60*> \param[in] TAU 61*> \verbatim 62*> TAU is REAL array, dimension (M) 63*> Details of the Householder transformations as returned by 64*> STZRQF. 65*> \endverbatim 66*> 67*> \param[out] WORK 68*> \verbatim 69*> WORK is REAL array, dimension (LWORK) 70*> \endverbatim 71*> 72*> \param[in] LWORK 73*> \verbatim 74*> LWORK is INTEGER 75*> length of WORK array. Must be >= N*N+N 76*> \endverbatim 77* 78* Authors: 79* ======== 80* 81*> \author Univ. of Tennessee 82*> \author Univ. of California Berkeley 83*> \author Univ. of Colorado Denver 84*> \author NAG Ltd. 85* 86*> \date November 2011 87* 88*> \ingroup single_lin 89* 90* ===================================================================== 91 REAL FUNCTION STZT02( M, N, AF, LDA, TAU, WORK, 92 $ LWORK ) 93* 94* -- LAPACK test routine (version 3.4.0) -- 95* -- LAPACK is a software package provided by Univ. of Tennessee, -- 96* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- 97* November 2011 98* 99* .. Scalar Arguments .. 100 INTEGER LDA, LWORK, M, N 101* .. 102* .. Array Arguments .. 103 REAL AF( LDA, * ), TAU( * ), WORK( LWORK ) 104* .. 105* 106* ===================================================================== 107* 108* .. Parameters .. 109 REAL ZERO, ONE 110 PARAMETER ( ZERO = 0.0E0, ONE = 1.0E0 ) 111* .. 112* .. Local Scalars .. 113 INTEGER I 114* .. 115* .. Local Arrays .. 116 REAL RWORK( 1 ) 117* .. 118* .. External Functions .. 119 REAL SLAMCH, SLANGE 120 EXTERNAL SLAMCH, SLANGE 121* .. 122* .. External Subroutines .. 123 EXTERNAL SLATZM, SLASET, XERBLA 124* .. 125* .. Intrinsic Functions .. 126 INTRINSIC MAX, REAL 127* .. 128* .. Executable Statements .. 129* 130 STZT02 = ZERO 131* 132 IF( LWORK.LT.N*N+N ) THEN 133 CALL XERBLA( 'STZT02', 7 ) 134 RETURN 135 END IF 136* 137* Quick return if possible 138* 139 IF( M.LE.0 .OR. N.LE.0 ) 140 $ RETURN 141* 142* Q := I 143* 144 CALL SLASET( 'Full', N, N, ZERO, ONE, WORK, N ) 145* 146* Q := P(1) * ... * P(m) * Q 147* 148 DO 10 I = M, 1, -1 149 CALL SLATZM( 'Left', N-M+1, N, AF( I, M+1 ), LDA, TAU( I ), 150 $ WORK( I ), WORK( M+1 ), N, WORK( N*N+1 ) ) 151 10 CONTINUE 152* 153* Q := P(m) * ... * P(1) * Q 154* 155 DO 20 I = 1, M 156 CALL SLATZM( 'Left', N-M+1, N, AF( I, M+1 ), LDA, TAU( I ), 157 $ WORK( I ), WORK( M+1 ), N, WORK( N*N+1 ) ) 158 20 CONTINUE 159* 160* Q := Q - I 161* 162 DO 30 I = 1, N 163 WORK( ( I-1 )*N+I ) = WORK( ( I-1 )*N+I ) - ONE 164 30 CONTINUE 165* 166 STZT02 = SLANGE( 'One-norm', N, N, WORK, N, RWORK ) / 167 $ ( SLAMCH( 'Epsilon' )*REAL( MAX( M, N ) ) ) 168 RETURN 169* 170* End of STZT02 171* 172 END 173