3 * =========== DOCUMENTATION ===========
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6 * http://www.netlib.org/lapack/explore-html/
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21 * SUBROUTINE SGGGLM( N, M, P, A, LDA, B, LDB, D, X, Y, WORK, LWORK,
24 * .. Scalar Arguments ..
25 * INTEGER INFO, LDA, LDB, LWORK, M, N, P
27 * .. Array Arguments ..
28 * REAL A( LDA, * ), B( LDB, * ), D( * ), WORK( * ),
38 *> SGGGLM solves a general Gauss-Markov linear model (GLM) problem:
40 *> minimize || y ||_2 subject to d = A*x + B*y
43 *> where A is an N-by-M matrix, B is an N-by-P matrix, and d is a
44 *> given N-vector. It is assumed that M <= N <= M+P, and
46 *> rank(A) = M and rank( A B ) = N.
48 *> Under these assumptions, the constrained equation is always
49 *> consistent, and there is a unique solution x and a minimal 2-norm
50 *> solution y, which is obtained using a generalized QR factorization
51 *> of the matrices (A, B) given by
53 *> A = Q*(R), B = Q*T*Z.
56 *> In particular, if matrix B is square nonsingular, then the problem
57 *> GLM is equivalent to the following weighted linear least squares
60 *> minimize || inv(B)*(d-A*x) ||_2
63 *> where inv(B) denotes the inverse of B.
72 *> The number of rows of the matrices A and B. N >= 0.
78 *> The number of columns of the matrix A. 0 <= M <= N.
84 *> The number of columns of the matrix B. P >= N-M.
89 *> A is REAL array, dimension (LDA,M)
90 *> On entry, the N-by-M matrix A.
91 *> On exit, the upper triangular part of the array A contains
92 *> the M-by-M upper triangular matrix R.
98 *> The leading dimension of the array A. LDA >= max(1,N).
103 *> B is REAL array, dimension (LDB,P)
104 *> On entry, the N-by-P matrix B.
105 *> On exit, if N <= P, the upper triangle of the subarray
106 *> B(1:N,P-N+1:P) contains the N-by-N upper triangular matrix T;
107 *> if N > P, the elements on and above the (N-P)th subdiagonal
108 *> contain the N-by-P upper trapezoidal matrix T.
114 *> The leading dimension of the array B. LDB >= max(1,N).
119 *> D is REAL array, dimension (N)
120 *> On entry, D is the left hand side of the GLM equation.
121 *> On exit, D is destroyed.
126 *> X is REAL array, dimension (M)
131 *> Y is REAL array, dimension (P)
133 *> On exit, X and Y are the solutions of the GLM problem.
138 *> WORK is REAL array, dimension (MAX(1,LWORK))
139 *> On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
145 *> The dimension of the array WORK. LWORK >= max(1,N+M+P).
146 *> For optimum performance, LWORK >= M+min(N,P)+max(N,P)*NB,
147 *> where NB is an upper bound for the optimal blocksizes for
148 *> SGEQRF, SGERQF, SORMQR and SORMRQ.
150 *> If LWORK = -1, then a workspace query is assumed; the routine
151 *> only calculates the optimal size of the WORK array, returns
152 *> this value as the first entry of the WORK array, and no error
153 *> message related to LWORK is issued by XERBLA.
159 *> = 0: successful exit.
160 *> < 0: if INFO = -i, the i-th argument had an illegal value.
161 *> = 1: the upper triangular factor R associated with A in the
162 *> generalized QR factorization of the pair (A, B) is
163 *> singular, so that rank(A) < M; the least squares
164 *> solution could not be computed.
165 *> = 2: the bottom (N-M) by (N-M) part of the upper trapezoidal
166 *> factor T associated with B in the generalized QR
167 *> factorization of the pair (A, B) is singular, so that
168 *> rank( A B ) < N; the least squares solution could not
175 *> \author Univ. of Tennessee
176 *> \author Univ. of California Berkeley
177 *> \author Univ. of Colorado Denver
180 *> \date November 2015
182 *> \ingroup realOTHEReigen
184 * =====================================================================
185 SUBROUTINE SGGGLM( N, M, P, A, LDA, B, LDB, D, X, Y, WORK, LWORK,
188 * -- LAPACK driver routine (version 3.6.0) --
189 * -- LAPACK is a software package provided by Univ. of Tennessee, --
190 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
193 * .. Scalar Arguments ..
194 INTEGER INFO, LDA, LDB, LWORK, M, N, P
196 * .. Array Arguments ..
197 REAL A( LDA, * ), B( LDB, * ), D( * ), WORK( * ),
201 * ===================================================================
205 PARAMETER ( ZERO = 0.0E+0, ONE = 1.0E+0 )
207 * .. Local Scalars ..
209 INTEGER I, LOPT, LWKMIN, LWKOPT, NB, NB1, NB2, NB3,
212 * .. External Subroutines ..
213 EXTERNAL SCOPY, SGEMV, SGGQRF, SORMQR, SORMRQ, STRTRS,
216 * .. External Functions ..
220 * .. Intrinsic Functions ..
221 INTRINSIC INT, MAX, MIN
223 * .. Executable Statements ..
225 * Test the input parameters
229 LQUERY = ( LWORK.EQ.-1 )
232 ELSE IF( M.LT.0 .OR. M.GT.N ) THEN
234 ELSE IF( P.LT.0 .OR. P.LT.N-M ) THEN
236 ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
238 ELSE IF( LDB.LT.MAX( 1, N ) ) THEN
242 * Calculate workspace
249 NB1 = ILAENV( 1, 'SGEQRF', ' ', N, M, -1, -1 )
250 NB2 = ILAENV( 1, 'SGERQF', ' ', N, M, -1, -1 )
251 NB3 = ILAENV( 1, 'SORMQR', ' ', N, M, P, -1 )
252 NB4 = ILAENV( 1, 'SORMRQ', ' ', N, M, P, -1 )
253 NB = MAX( NB1, NB2, NB3, NB4 )
255 LWKOPT = M + NP + MAX( N, P )*NB
259 IF( LWORK.LT.LWKMIN .AND. .NOT.LQUERY ) THEN
265 CALL XERBLA( 'SGGGLM', -INFO )
267 ELSE IF( LQUERY ) THEN
271 * Quick return if possible
276 * Compute the GQR factorization of matrices A and B:
278 * Q**T*A = ( R11 ) M, Q**T*B*Z**T = ( T11 T12 ) M
279 * ( 0 ) N-M ( 0 T22 ) N-M
282 * where R11 and T22 are upper triangular, and Q and Z are
285 CALL SGGQRF( N, M, P, A, LDA, WORK, B, LDB, WORK( M+1 ),
286 $ WORK( M+NP+1 ), LWORK-M-NP, INFO )
287 LOPT = WORK( M+NP+1 )
289 * Update left-hand-side vector d = Q**T*d = ( d1 ) M
292 CALL SORMQR( 'Left', 'Transpose', N, 1, M, A, LDA, WORK, D,
293 $ MAX( 1, N ), WORK( M+NP+1 ), LWORK-M-NP, INFO )
294 LOPT = MAX( LOPT, INT( WORK( M+NP+1 ) ) )
296 * Solve T22*y2 = d2 for y2
299 CALL STRTRS( 'Upper', 'No transpose', 'Non unit', N-M, 1,
300 $ B( M+1, M+P-N+1 ), LDB, D( M+1 ), N-M, INFO )
307 CALL SCOPY( N-M, D( M+1 ), 1, Y( M+P-N+1 ), 1 )
312 DO 10 I = 1, M + P - N
316 * Update d1 = d1 - T12*y2
318 CALL SGEMV( 'No transpose', M, N-M, -ONE, B( 1, M+P-N+1 ), LDB,
319 $ Y( M+P-N+1 ), 1, ONE, D, 1 )
321 * Solve triangular system: R11*x = d1
324 CALL STRTRS( 'Upper', 'No Transpose', 'Non unit', M, 1, A, LDA,
334 CALL SCOPY( M, D, 1, X, 1 )
337 * Backward transformation y = Z**T *y
339 CALL SORMRQ( 'Left', 'Transpose', P, 1, NP,
340 $ B( MAX( 1, N-P+1 ), 1 ), LDB, WORK( M+1 ), Y,
341 $ MAX( 1, P ), WORK( M+NP+1 ), LWORK-M-NP, INFO )
342 WORK( 1 ) = M + NP + MAX( LOPT, INT( WORK( M+NP+1 ) ) )