dgels - solve overdetermined or underdetermined real linear systems involving an M-by-N matrix A, or its transpose, using a QR or LQ factorization of A
SUBROUTINE DGELS( TRANSA, M, N, NRHS, A, LDA, B, LDB, WORK, LDWORK, * INFO) CHARACTER * 1 TRANSA INTEGER M, N, NRHS, LDA, LDB, LDWORK, INFO DOUBLE PRECISION A(LDA,*), B(LDB,*), WORK(*)
SUBROUTINE DGELS_64( TRANSA, M, N, NRHS, A, LDA, B, LDB, WORK, * LDWORK, INFO) CHARACTER * 1 TRANSA INTEGER*8 M, N, NRHS, LDA, LDB, LDWORK, INFO DOUBLE PRECISION A(LDA,*), B(LDB,*), WORK(*)
SUBROUTINE GELS( [TRANSA], [M], [N], [NRHS], A, [LDA], B, [LDB], * [WORK], [LDWORK], [INFO]) CHARACTER(LEN=1) :: TRANSA INTEGER :: M, N, NRHS, LDA, LDB, LDWORK, INFO REAL(8), DIMENSION(:) :: WORK REAL(8), DIMENSION(:,:) :: A, B
SUBROUTINE GELS_64( [TRANSA], [M], [N], [NRHS], A, [LDA], B, [LDB], * [WORK], [LDWORK], [INFO]) CHARACTER(LEN=1) :: TRANSA INTEGER(8) :: M, N, NRHS, LDA, LDB, LDWORK, INFO REAL(8), DIMENSION(:) :: WORK REAL(8), DIMENSION(:,:) :: A, B
#include <sunperf.h>
void dgels(char transa, int m, int n, int nrhs, double *a, int lda, double *b, int ldb, int *info);
void dgels_64(char transa, long m, long n, long nrhs, double *a, long lda, double *b, long ldb, long *info);
dgels solves overdetermined or underdetermined real linear systems involving an M-by-N matrix A, or its transpose, using a QR or LQ factorization of A. It is assumed that A has full rank.
The following options are provided:
1. If TRANS = 'N' and m >= n: find the least squares solution of an overdetermined system, i.e., solve the least squares problem minimize || B - A*X ||.
2. If TRANS = 'N' and m < n: find the minimum norm solution of an underdetermined system A * X = B.
3. If TRANS = 'T' and m >= n: find the minimum norm solution of an undetermined system A**T * X = B.
4. If TRANS = 'T' and m < n: find the least squares solution of an overdetermined system, i.e., solve the least squares problem minimize || B - A**T * X ||.
Several right hand side vectors b and solution vectors x can be handled in a single call; they are stored as the columns of the M-by-NRHS right hand side matrix B and the N-by-NRHS solution matrix X.
= 'N': the linear system involves A;
= 'T': the linear system involves A**T.
WORK(1)
returns the optimal LDWORK.
min(M,N)
and NB is the optimum block size.
If LDWORK = -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 LDWORK is issued by XERBLA.
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value