LAPACK  3.4.1
LAPACK: Linear Algebra PACKage
sgqrts.f
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00001 *> \brief \b SGQRTS
00002 *
00003 *  =========== DOCUMENTATION ===========
00004 *
00005 * Online html documentation available at 
00006 *            http://www.netlib.org/lapack/explore-html/ 
00007 *
00008 *  Definition:
00009 *  ===========
00010 *
00011 *       SUBROUTINE SGQRTS( N, M, P, A, AF, Q, R, LDA, TAUA, B, BF, Z, T,
00012 *                          BWK, LDB, TAUB, WORK, LWORK, RWORK, RESULT )
00013 * 
00014 *       .. Scalar Arguments ..
00015 *       INTEGER            LDA, LDB, LWORK, M, P, N
00016 *       ..
00017 *       .. Array Arguments ..
00018 *       REAL               A( LDA, * ), AF( LDA, * ), R( LDA, * ),
00019 *      $                   Q( LDA, * ), B( LDB, * ), BF( LDB, * ),
00020 *      $                   T( LDB, * ), Z( LDB, * ), BWK( LDB, * ),
00021 *      $                   TAUA( * ), TAUB( * ), RESULT( 4 ),
00022 *      $                   RWORK( * ), WORK( LWORK )
00023 *       ..
00024 *  
00025 *
00026 *> \par Purpose:
00027 *  =============
00028 *>
00029 *> \verbatim
00030 *>
00031 *> SGQRTS tests SGGQRF, which computes the GQR factorization of an
00032 *> N-by-M matrix A and a N-by-P matrix B: A = Q*R and B = Q*T*Z.
00033 *> \endverbatim
00034 *
00035 *  Arguments:
00036 *  ==========
00037 *
00038 *> \param[in] N
00039 *> \verbatim
00040 *>          N is INTEGER
00041 *>          The number of rows of the matrices A and B.  N >= 0.
00042 *> \endverbatim
00043 *>
00044 *> \param[in] M
00045 *> \verbatim
00046 *>          M is INTEGER
00047 *>          The number of columns of the matrix A.  M >= 0.
00048 *> \endverbatim
00049 *>
00050 *> \param[in] P
00051 *> \verbatim
00052 *>          P is INTEGER
00053 *>          The number of columns of the matrix B.  P >= 0.
00054 *> \endverbatim
00055 *>
00056 *> \param[in] A
00057 *> \verbatim
00058 *>          A is REAL array, dimension (LDA,M)
00059 *>          The N-by-M matrix A.
00060 *> \endverbatim
00061 *>
00062 *> \param[out] AF
00063 *> \verbatim
00064 *>          AF is REAL array, dimension (LDA,N)
00065 *>          Details of the GQR factorization of A and B, as returned
00066 *>          by SGGQRF, see SGGQRF for further details.
00067 *> \endverbatim
00068 *>
00069 *> \param[out] Q
00070 *> \verbatim
00071 *>          Q is REAL array, dimension (LDA,N)
00072 *>          The M-by-M orthogonal matrix Q.
00073 *> \endverbatim
00074 *>
00075 *> \param[out] R
00076 *> \verbatim
00077 *>          R is REAL array, dimension (LDA,MAX(M,N))
00078 *> \endverbatim
00079 *>
00080 *> \param[in] LDA
00081 *> \verbatim
00082 *>          LDA is INTEGER
00083 *>          The leading dimension of the arrays A, AF, R and Q.
00084 *>          LDA >= max(M,N).
00085 *> \endverbatim
00086 *>
00087 *> \param[out] TAUA
00088 *> \verbatim
00089 *>          TAUA is REAL array, dimension (min(M,N))
00090 *>          The scalar factors of the elementary reflectors, as returned
00091 *>          by SGGQRF.
00092 *> \endverbatim
00093 *>
00094 *> \param[in] B
00095 *> \verbatim
00096 *>          B is REAL array, dimension (LDB,P)
00097 *>          On entry, the N-by-P matrix A.
00098 *> \endverbatim
00099 *>
00100 *> \param[out] BF
00101 *> \verbatim
00102 *>          BF is REAL array, dimension (LDB,N)
00103 *>          Details of the GQR factorization of A and B, as returned
00104 *>          by SGGQRF, see SGGQRF for further details.
00105 *> \endverbatim
00106 *>
00107 *> \param[out] Z
00108 *> \verbatim
00109 *>          Z is REAL array, dimension (LDB,P)
00110 *>          The P-by-P orthogonal matrix Z.
00111 *> \endverbatim
00112 *>
00113 *> \param[out] T
00114 *> \verbatim
00115 *>          T is REAL array, dimension (LDB,max(P,N))
00116 *> \endverbatim
00117 *>
00118 *> \param[out] BWK
00119 *> \verbatim
00120 *>          BWK is REAL array, dimension (LDB,N)
00121 *> \endverbatim
00122 *>
00123 *> \param[in] LDB
00124 *> \verbatim
00125 *>          LDB is INTEGER
00126 *>          The leading dimension of the arrays B, BF, Z and T.
00127 *>          LDB >= max(P,N).
00128 *> \endverbatim
00129 *>
00130 *> \param[out] TAUB
00131 *> \verbatim
00132 *>          TAUB is REAL array, dimension (min(P,N))
00133 *>          The scalar factors of the elementary reflectors, as returned
00134 *>          by SGGRQF.
00135 *> \endverbatim
00136 *>
00137 *> \param[out] WORK
00138 *> \verbatim
00139 *>          WORK is REAL array, dimension (LWORK)
00140 *> \endverbatim
00141 *>
00142 *> \param[in] LWORK
00143 *> \verbatim
00144 *>          LWORK is INTEGER
00145 *>          The dimension of the array WORK, LWORK >= max(N,M,P)**2.
00146 *> \endverbatim
00147 *>
00148 *> \param[out] RWORK
00149 *> \verbatim
00150 *>          RWORK is REAL array, dimension (max(N,M,P))
00151 *> \endverbatim
00152 *>
00153 *> \param[out] RESULT
00154 *> \verbatim
00155 *>          RESULT is REAL array, dimension (4)
00156 *>          The test ratios:
00157 *>            RESULT(1) = norm( R - Q'*A ) / ( MAX(M,N)*norm(A)*ULP)
00158 *>            RESULT(2) = norm( T*Z - Q'*B ) / (MAX(P,N)*norm(B)*ULP)
00159 *>            RESULT(3) = norm( I - Q'*Q ) / ( M*ULP )
00160 *>            RESULT(4) = norm( I - Z'*Z ) / ( P*ULP )
00161 *> \endverbatim
00162 *
00163 *  Authors:
00164 *  ========
00165 *
00166 *> \author Univ. of Tennessee 
00167 *> \author Univ. of California Berkeley 
00168 *> \author Univ. of Colorado Denver 
00169 *> \author NAG Ltd. 
00170 *
00171 *> \date November 2011
00172 *
00173 *> \ingroup single_eig
00174 *
00175 *  =====================================================================
00176       SUBROUTINE SGQRTS( N, M, P, A, AF, Q, R, LDA, TAUA, B, BF, Z, T,
00177      $                   BWK, LDB, TAUB, WORK, LWORK, RWORK, RESULT )
00178 *
00179 *  -- LAPACK test routine (version 3.4.0) --
00180 *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
00181 *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
00182 *     November 2011
00183 *
00184 *     .. Scalar Arguments ..
00185       INTEGER            LDA, LDB, LWORK, M, P, N
00186 *     ..
00187 *     .. Array Arguments ..
00188       REAL               A( LDA, * ), AF( LDA, * ), R( LDA, * ),
00189      $                   Q( LDA, * ), B( LDB, * ), BF( LDB, * ),
00190      $                   T( LDB, * ), Z( LDB, * ), BWK( LDB, * ),
00191      $                   TAUA( * ), TAUB( * ), RESULT( 4 ),
00192      $                   RWORK( * ), WORK( LWORK )
00193 *     ..
00194 *
00195 *  =====================================================================
00196 *
00197 *     .. Parameters ..
00198       REAL               ZERO, ONE
00199       PARAMETER          ( ZERO = 0.0E+0, ONE = 1.0E+0 )
00200       REAL               ROGUE
00201       PARAMETER          ( ROGUE = -1.0E+10 )
00202 *     ..
00203 *     .. Local Scalars ..
00204       INTEGER            INFO
00205       REAL               ANORM, BNORM, ULP, UNFL, RESID
00206 *     ..
00207 *     .. External Functions ..
00208       REAL               SLAMCH, SLANGE, SLANSY
00209       EXTERNAL           SLAMCH, SLANGE, SLANSY
00210 *     ..
00211 *     .. External Subroutines ..
00212       EXTERNAL           SGEMM, SLACPY, SLASET, SORGQR,
00213      $                   SORGRQ, SSYRK
00214 *     ..
00215 *     .. Intrinsic Functions ..
00216       INTRINSIC          MAX, MIN, REAL
00217 *     ..
00218 *     .. Executable Statements ..
00219 *
00220       ULP = SLAMCH( 'Precision' )
00221       UNFL = SLAMCH( 'Safe minimum' )
00222 *
00223 *     Copy the matrix A to the array AF.
00224 *
00225       CALL SLACPY( 'Full', N, M, A, LDA, AF, LDA )
00226       CALL SLACPY( 'Full', N, P, B, LDB, BF, LDB )
00227 *
00228       ANORM = MAX( SLANGE( '1', N, M, A, LDA, RWORK ), UNFL )
00229       BNORM = MAX( SLANGE( '1', N, P, B, LDB, RWORK ), UNFL )
00230 *
00231 *     Factorize the matrices A and B in the arrays AF and BF.
00232 *
00233       CALL SGGQRF( N, M, P, AF, LDA, TAUA, BF, LDB, TAUB, WORK,
00234      $             LWORK, INFO )
00235 *
00236 *     Generate the N-by-N matrix Q
00237 *
00238       CALL SLASET( 'Full', N, N, ROGUE, ROGUE, Q, LDA )
00239       CALL SLACPY( 'Lower', N-1, M, AF( 2,1 ), LDA, Q( 2,1 ), LDA )
00240       CALL SORGQR( N, N, MIN( N, M ), Q, LDA, TAUA, WORK, LWORK, INFO )
00241 *
00242 *     Generate the P-by-P matrix Z
00243 *
00244       CALL SLASET( 'Full', P, P, ROGUE, ROGUE, Z, LDB )
00245       IF( N.LE.P ) THEN
00246          IF( N.GT.0 .AND. N.LT.P )
00247      $      CALL SLACPY( 'Full', N, P-N, BF, LDB, Z( P-N+1, 1 ), LDB )
00248          IF( N.GT.1 )
00249      $      CALL SLACPY( 'Lower', N-1, N-1, BF( 2, P-N+1 ), LDB,
00250      $                    Z( P-N+2, P-N+1 ), LDB )
00251       ELSE
00252          IF( P.GT.1)
00253      $      CALL SLACPY( 'Lower', P-1, P-1, BF( N-P+2, 1 ), LDB,
00254      $                    Z( 2, 1 ), LDB )
00255       END IF
00256       CALL SORGRQ( P, P, MIN( N, P ), Z, LDB, TAUB, WORK, LWORK, INFO )
00257 *
00258 *     Copy R
00259 *
00260       CALL SLASET( 'Full', N, M, ZERO, ZERO, R, LDA )
00261       CALL SLACPY( 'Upper', N, M, AF, LDA, R, LDA )
00262 *
00263 *     Copy T
00264 *
00265       CALL SLASET( 'Full', N, P, ZERO, ZERO, T, LDB )
00266       IF( N.LE.P ) THEN
00267          CALL SLACPY( 'Upper', N, N, BF( 1, P-N+1 ), LDB, T( 1, P-N+1 ),
00268      $                LDB )
00269       ELSE
00270          CALL SLACPY( 'Full', N-P, P, BF, LDB, T, LDB )
00271          CALL SLACPY( 'Upper', P, P, BF( N-P+1, 1 ), LDB, T( N-P+1, 1 ),
00272      $                LDB )
00273       END IF
00274 *
00275 *     Compute R - Q'*A
00276 *
00277       CALL SGEMM( 'Transpose', 'No transpose', N, M, N, -ONE, Q, LDA, A,
00278      $            LDA, ONE, R, LDA )
00279 *
00280 *     Compute norm( R - Q'*A ) / ( MAX(M,N)*norm(A)*ULP ) .
00281 *
00282       RESID = SLANGE( '1', N, M, R, LDA, RWORK )
00283       IF( ANORM.GT.ZERO ) THEN
00284          RESULT( 1 ) = ( ( RESID / REAL( MAX(1,M,N) ) ) / ANORM ) / ULP
00285       ELSE
00286          RESULT( 1 ) = ZERO
00287       END IF
00288 *
00289 *     Compute T*Z - Q'*B
00290 *
00291       CALL SGEMM( 'No Transpose', 'No transpose', N, P, P, ONE, T, LDB,
00292      $            Z, LDB, ZERO, BWK, LDB )
00293       CALL SGEMM( 'Transpose', 'No transpose', N, P, N, -ONE, Q, LDA,
00294      $            B, LDB, ONE, BWK, LDB )
00295 *
00296 *     Compute norm( T*Z - Q'*B ) / ( MAX(P,N)*norm(A)*ULP ) .
00297 *
00298       RESID = SLANGE( '1', N, P, BWK, LDB, RWORK )
00299       IF( BNORM.GT.ZERO ) THEN
00300          RESULT( 2 ) = ( ( RESID / REAL( MAX(1,P,N ) ) )/BNORM ) / ULP
00301       ELSE
00302          RESULT( 2 ) = ZERO
00303       END IF
00304 *
00305 *     Compute I - Q'*Q
00306 *
00307       CALL SLASET( 'Full', N, N, ZERO, ONE, R, LDA )
00308       CALL SSYRK( 'Upper', 'Transpose', N, N, -ONE, Q, LDA, ONE, R,
00309      $            LDA )
00310 *
00311 *     Compute norm( I - Q'*Q ) / ( N * ULP ) .
00312 *
00313       RESID = SLANSY( '1', 'Upper', N, R, LDA, RWORK )
00314       RESULT( 3 ) = ( RESID / REAL( MAX( 1, N ) ) ) / ULP
00315 *
00316 *     Compute I - Z'*Z
00317 *
00318       CALL SLASET( 'Full', P, P, ZERO, ONE, T, LDB )
00319       CALL SSYRK( 'Upper', 'Transpose', P, P, -ONE, Z, LDB, ONE, T,
00320      $            LDB )
00321 *
00322 *     Compute norm( I - Z'*Z ) / ( P*ULP ) .
00323 *
00324       RESID = SLANSY( '1', 'Upper', P, T, LDB, RWORK )
00325       RESULT( 4 ) = ( RESID / REAL( MAX( 1, P ) ) ) / ULP
00326 *
00327       RETURN
00328 *
00329 *     End of SGQRTS
00330 *
00331       END
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