# dgglse.f - Man Page

## Synopsis

### Functions/Subroutines

subroutine **dgglse** (M, **N**, P, A, **LDA**, B, **LDB**, C, D, X, WORK, LWORK, INFO)

**DGGLSE solves overdetermined or underdetermined systems for OTHER matrices**

## Function/Subroutine Documentation

### subroutine dgglse (integer M, integer N, integer P, double precision, dimension( lda, * ) A, integer LDA, double precision, dimension( ldb, * ) B, integer LDB, double precision, dimension( * ) C, double precision, dimension( * ) D, double precision, dimension( * ) X, double precision, dimension( * ) WORK, integer LWORK, integer INFO)

**DGGLSE solves overdetermined or underdetermined systems for OTHER matrices**

**Purpose:**

DGGLSE solves the linear equality-constrained least squares (LSE) problem: minimize || c - A*x ||_2 subject to B*x = d where A is an M-by-N matrix, B is a P-by-N matrix, c is a given M-vector, and d is a given P-vector. It is assumed that P <= N <= M+P, and rank(B) = P and rank( (A) ) = N. ( (B) ) These conditions ensure that the LSE problem has a unique solution, which is obtained using a generalized RQ factorization of the matrices (B, A) given by B = (0 R)*Q, A = Z*T*Q.

**Parameters:***M*M is INTEGER The number of rows of the matrix A. M >= 0.

*N*N is INTEGER The number of columns of the matrices A and B. N >= 0.

*P*P is INTEGER The number of rows of the matrix B. 0 <= P <= N <= M+P.

*A*A is DOUBLE PRECISION array, dimension (LDA,N) On entry, the M-by-N matrix A. On exit, the elements on and above the diagonal of the array contain the min(M,N)-by-N upper trapezoidal matrix T.

*LDA*LDA is INTEGER The leading dimension of the array A. LDA >= max(1,M).

*B*B is DOUBLE PRECISION array, dimension (LDB,N) On entry, the P-by-N matrix B. On exit, the upper triangle of the subarray B(1:P,N-P+1:N) contains the P-by-P upper triangular matrix R.

*LDB*LDB is INTEGER The leading dimension of the array B. LDB >= max(1,P).

*C*C is DOUBLE PRECISION array, dimension (M) On entry, C contains the right hand side vector for the least squares part of the LSE problem. On exit, the residual sum of squares for the solution is given by the sum of squares of elements N-P+1 to M of vector C.

*D*D is DOUBLE PRECISION array, dimension (P) On entry, D contains the right hand side vector for the constrained equation. On exit, D is destroyed.

*X*X is DOUBLE PRECISION array, dimension (N) On exit, X is the solution of the LSE problem.

*WORK*WORK is DOUBLE PRECISION array, dimension (MAX(1,LWORK)) On exit, if INFO = 0, WORK(1) returns the optimal LWORK.

*LWORK*LWORK is INTEGER The dimension of the array WORK. LWORK >= max(1,M+N+P). For optimum performance LWORK >= P+min(M,N)+max(M,N)*NB, where NB is an upper bound for the optimal blocksizes for DGEQRF, SGERQF, DORMQR and SORMRQ. If LWORK = -1, then a workspace query is assumed; the routine only calculates the optimal size of the WORK array, returns this value as the first entry of the WORK array, and no error message related to LWORK is issued by XERBLA.

*INFO*INFO is INTEGER = 0: successful exit. < 0: if INFO = -i, the i-th argument had an illegal value. = 1: the upper triangular factor R associated with B in the generalized RQ factorization of the pair (B, A) is singular, so that rank(B) < P; the least squares solution could not be computed. = 2: the (N-P) by (N-P) part of the upper trapezoidal factor T associated with A in the generalized RQ factorization of the pair (B, A) is singular, so that rank( (A) ) < N; the least squares solution could not ( (B) ) be computed.

**Author:**Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

**Date:**December 2016

Definition at line 182 of file dgglse.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page dgglse(3) is an alias of dgglse.f(3).

Tue Nov 14 2017 Version 3.8.0 LAPACK